coolant system circulation

[FLENG2008]

hello all
i have a 1.9 tdi 115 and i could do with some of your ideas
i have a problem with the circulation of the coolant, i think its an air lock but i also think i may have a blockage and thats why i cant get the air out..
sometimes the heater drops cold, and when you check under the bonnet the top hose is hot along with a few other and bottom hose getts slightly warm at the top
from what i can feel the rad gets hot but not sure if this has a blockage as i cant seem to get this air lock out
after a run the bottom hose still doesnt get warm all the way down just still at the top and the expansion cap hisses air slightly
it never over heats but it has crept up over 90 degrees a couple of times when i peg it down the dual carrage way
i have had a sniffer test so its not the head gasket
i have had a cap fitted
i had a slight water leak but now fixed

not sure exactly what is wrong with it, i have a feeling its the rad thats blocked, cause ive never heard the fan switch cut in and the fresh coolant thats was put in recently has now turned a bit rusty coloured

anyway please help cause i dont want to get head gasket problems from a stupid air lock:aargh4:

thankyou

[zollaf]

water pump, i think. these are self bleeding, so shouldny air lock. incidentally, the sniffer test( blue fluid that turns green/yellow)are unreliable on a diesel. if it does change colour, you have a blown gasket, if it doesnt change, it means nothing.

[kite]

As Zollaf says waterpump, these are known to fail, also a good idea to change the stat

[FLENG2008]

ok if you guys are sure ill go for that
is there anyway to tell for sure or is it trial and error..

[herby0001]

My money is on the waterpump. There have been previous posts on the forum regarding the heater blowing hot and cold and it's been just that. The coolant isn't getting pushed round the system properly, hencte the hot & cold heater and dodgy rad.

[FLENG2008]

thanks for the replies
appreciate it...

[FLENG2008]

swapped the pump but the old one was fine

anyone got any more idea's

[FLENG2008]

ended up being the thermostat

i was under the impression the thermostat was in the top of the top hose because the top hose got hot first
i didnt know until today it was in the bottom hose, i would of thought that anyone who knew that the thermostat was in the bottom hose would have pointed me in that direction first as the bottom hose only getting slightly warm at the top would have been a big indicator that the thermostat was blocked shut

so if your bottom hose doesn't get hot and your car overheats when going fast try your thermostat, it may not be water pump or head gasket like everyone assumes

[herby0001]

Thanks for pointing that out. Kite did suggest the 'stat', though like you and without consulting a Haynes manual, I would have assumed it was in a top hose too. We live and learn.

[FLENG2008]

i still have problems

sometimes the bottom hose gets hot but sometimes its stone cold
i think the thermostat housing maybe shot as i dont think the thermostat fitted in securley when i fitted it

and sometimes the heater fluctuate from warm to cold, they never really gett hott like my other tdi

just to let you know ive had a
thermostat
water pump
expansion cap
pressure test
sniffer test

i have a feeling i have a blockage or something simular, like radiator cause the coolant just doesnt seem to flow around like it should
any help appreciated
thanks for reading

[Col]

Your head gasket has failed and it will only get worse.

115hp AJM TDI's are notorious for this.

The mode of failure is not that of what is considered a classic head gasket failure and can be very hard to detect.

Take it to a specialist to confirm the diagnosis. A normal garage will probably go along the stat / water pump route, a specialist won't, they will go striaght for and investigate the HG.

[FLENG2008]

ok ive had a sniffer what else can i do to check the gasket?
thanks

[herby0001]

Probably best then to drop the rad, flush it out with a hose. You could also check for blockages by putting the hose into a coolant pipe and see if it flows through the engine block too. Maybe narrow it down that way?

[FLENG2008]

ok thanks

i was gonna give that a try before HG anyway

any other suggestions? or options i could try before i bite the bullet or if theres any way i could check if it is the gasket before i try more guess work

thanks for the replies

[AJB]

...and the fresh coolant thats was put in recently has now turned a bit rusty coloured

Was it the right sort of coolant that was added? If the factory G12 (pinky purpley colour) is mixed with the wrong sort of stuff, I think it can form brown sludge... Could that be blocking up the thermostat etc?

If so, then it might just need draining, a complete flush, and then filling with the correct coolant.

[FLENG2008]

yes it was g12
im gonna try a flush and see but i think its more than that, for some reason it doesnt seem to circulate fully, what should i use to flush it out with? i dont think its the head gasket but im running out of other options now

ill try a flush and im getting a block test done to see if that shows anything

[AJB]

yes it was g12
And was it definitely G12 that was in there before? I've just got a feeling that you get brown sludge if they mix, and I can't quite see why else your new coolant would have gone rusty coloured.


what should i use to flush it out with?
Someone else might have a better plan, but if it was me I'd just drain, fill with water, run for a bit to flush it round and repeat until the water stays clear. Then drain once more and fill with the correct coolant.

Don't know if the heater control on these is in the water flow or air flow, but might as well have the heater on hot whilst you're doing it.

[AJB]

Just to add, I'd run it up to temperature with just water in, so that the thermostat gets to open and the water gets to flow through the radiator too.

[FLENG2008]

alright thanks for the replys i will try that..

[FLENG2008]

i havent flushed it yet but i have noticed i deff have a circulation problem

am i right in thinking that the flow of the coolant is supposed to:

start in the engine and warm up
then the thermostat will open and the bottom hose gets hot and then the rad gets hot and pushes the cooler water back into the engine and so on..

[AJB]

I may get this very wrong, but my understanding is:

When the engine is cold, the thermostat is shut so the water pump just pumps water around the engine.

The engine warms up, and the thermostat (immersed in the water flowing round the engine, so it knows how hot it is) starts to open.

Once the thermostat is partly open, the water pump can suck cool water into the engine from the bottom of the radiator (where it is coolest, as hot water rises, cool water sinks), or pump hot water into the top of the radiator. There's no real difference between those two statements - the pump is both sucking and pushing, and whereever it is in the flow, the effect is the same - water is pushed through the radiator, and so cooled down.

In terms of the flow it doesn't matter whether the thermostat is near where the top hose joins the engine or the bottom hose - whether you close a tap on the way into the radiator or on the way out it'll have the same effect - water won't be able to flow. The difference is just in which temperature it's keeping constant. If it's at the top, then it's keeping the hot water coming out of the engine at a fixed temperature, and allowing more through the radiator if it gets too hot. If it's at the bottom, then it's keeping the cool water flowing into the engine at a fixed temperature, again allowing more through the radiator if it gets too hot. The difference is just that if the engine is producing more heat (ie working hard), do you want it to get hotter at the top (ie water coming into the bottom is at constant temperature), or colder at the bottom (ie water going out of the top is at constant temperature).

I've certainly worked on old cars where the thermostat is in the flow to the top radiator hose, but could well believe it might be by the bottom hose on others. I'm afraid I've no idea where it actually is on the VW - haven't had to change mine yet!

Hope that's some use - and hope it's right! Hopefully someone else will correct me if I'm wrong...

[FLENG2008]

I may get this very wrong, but my understanding is:

When the engine is cold, the thermostat is shut so the water pump just pumps water around the engine.

The engine warms up, and the thermostat (immersed in the water flowing round the engine, so it knows how hot it is) starts to open.

Once the thermostat is partly open, the water pump can suck cool water into the engine from the bottom of the radiator (where it is coolest, as hot water rises, cool water sinks), or pump hot water into the top of the radiator. There's no real difference between those two statements - the pump is both sucking and pushing, and whereever it is in the flow, the effect is the same - water is pushed through the radiator, and so cooled down.

In terms of the flow it doesn't matter whether the thermostat is near where the top hose joins the engine or the bottom hose - whether you close a tap on the way into the radiator or on the way out it'll have the same effect - water won't be able to flow. The difference is just in which temperature it's keeping constant. If it's at the top, then it's keeping the hot water coming out of the engine at a fixed temperature, and allowing more through the radiator if it gets too hot. If it's at the bottom, then it's keeping the cool water flowing into the engine at a fixed temperature, again allowing more through the radiator if it gets too hot. The difference is just that if the engine is producing more heat (ie working hard), do you want it to get hotter at the top (ie water coming into the bottom is at constant temperature), or colder at the bottom (ie water going out of the top is at constant temperature).

I've certainly worked on old cars where the thermostat is in the flow to the top radiator hose, but could well believe it might be by the bottom hose on others. I'm afraid I've no idea where it actually is on the VW - haven't had to change mine yet!

Hope that's some use - and hope it's right! Hopefully someone else will correct me if I'm wrong...

the stat is in the bottom hose which confused me a first cause evryother car ive had has been in the top hose

but you are right in what your saying, the water pump is pumping it all around, its just that the stat being in the bottom hose to me it just seems like that is the one that should get hot first, but on mine the top hose getts really hot first and sometimes cause's the rad fan to cut in but the bottom hose can still be cold (which is not the right way round), i could be wrong but it seems like my coolant is flowing the wrong way around, alot of plp suggesting head gasket but im not compeltely sure yet, fluctuating heaters and heaters never getting hott like they should, doing my head in

[kite]

i havent flushed it yet but i have noticed i deff have a circulation problem

am i right in thinking that the flow of the coolant is supposed to:

start in the engine and warm up
then the thermostat will open and the bottom hose gets hot and then the rad gets hot and pushes the cooler water back into the engine and so on..
You could have a waterpump starting to break up

[zollaf]

kite, weve all told him already to change his waterpump, including you, 2 pages ago.:D.

[pon]

swapped the pump but the old one was fine

anyone got any more idea's


Fleng2008 says that he has replaced the water pump

[kite]

kite, weve all told him already to change his waterpump, including you, 2 pages ago.:D.

Doh..............:Blush2:

[zollaf]

:biglaugh:

[AJB]

its just that the stat being in the bottom hose to me it just seems like that is the one that should get hot first
No - I'd still expect the top to get hot first. Wherever the stat is, I'd expect the engine to be sucking cooler water in from the bottom of the radiator and pumping hotter water into the top. From that point of view, it makes no difference which pipe the thermostat blocks off to reduce the flow. Doing it that way (cold from bottom of rad into engine) also means that the natural convection (hot water in the engine rises to the top, cold water in the radiator sinks to the bottom) will help out the water pump rather than fighting against it. I don't know about this particular engine, but I would still expect top to get hot first.


but on mine the top hose getts really hot first and sometimes cause's the rad fan to cut in but the bottom hose can still be cold
The rad fan should cut in when the rad gets too hot, or when the water coming out of the rad into the engine is too hot (assuming there's a separate switch for it somewhere, and depending on where it is). So if the circulation is ok, then I would expect the thermostat to be fully open and the bottom hose to be hot before the fan kicks in. If it isn't, it either implies that the coolant isn't circulating (so not being forced through rad for whatever reason), or that the fan switch is faulty and the fan is kicking in too early. It would be worth finding out where the fan switch is, and seeing whether that place is hot when the fan comes on.

Although the fan kicking in early wouldn't do much harm - the thermostat would close a bit to allow for the fact the rad is doing more cooling than before, and everything else should behave as normal.

Does the car ever overheat according to the temperature gauge? If the coolant isn't flowing through the rad, then the rad fan won't help cool it much, and I'd expect the temperature gauge to start to rise whilst the fan doesn't do much.

EDIT Having reread your original post:
OK it does creep above 90 degrees someimes. That implies circulation problem rather than fan coming on early. Or maybe head gasket as others have said causing exhaust gas to get into the coolant and heat it up more and/or introduce air locks.

[FLENG2008]

lol
yer thanks everyone
i have changed the pump and thermostat

i have just been out in the car and i did have heaters, they didn't get red hott but they wasn't bad, it did drop cold once but warm back up quickly when i continued driving
i felt the bottom hose and today it was starting to get hot at the top, but no where near as hot as the top hose

its really doing my head in now, some days the bottom hose doesnt get hot at all and ive got limited heating and hisses out the header tank, some days it acts half normal, its really strange

im still not sure whether it has any thing to do with the thermostat housing, cause when i replaced the stat it locked into place but it didnt look super tight in place as if it only locked in on one side of the housing, altho i could be being paranoid im really not sure

im just keeping the thread going as i cant get my head round it at all and has been an issue for a while now and im trying to get as many different opinions and options to try before i finally give in and go for the head gasket

as i mentioned in earlier posts im waiting for a block test and go from there but in the mean time just trying to figure out where its all going wrong :aargh4:

[AJB]

...and hisses out the header tank, some days it acts half normal, its really strange
Have to say hissing from tank after long run does sound a bit like head gasket. Once the coolant is all up to temperature, so has finished expanding, then whatever is coming out of the header tank must be coming from somewhere. If the car is actually boiling at that point, then coolant could be turning into steam (which is lots bigger), so the steam could hiss out. Or, if exhaust gasses are getting into the coolant (eg head gasket), then they will have to come out somewhere, and that will be through the header tank cap which has a pressure release valve in it...

[FLENG2008]

No - I'd still expect the top to get hot first. Wherever the stat is, I'd expect the engine to be sucking cooler water in from the bottom of the radiator and pumping hotter water into the top. From that point of view, it makes no difference which pipe the thermostat blocks off to reduce the flow. Doing it that way (cold from bottom of rad into engine) also means that the natural convection (hot water in the engine rises to the top, cold water in the radiator sinks to the bottom) will help out the water pump rather than fighting against it. I don't know about this particular engine, but I would still expect top to get hot first.


The rad fan should cut in when the rad gets too hot, or when the water coming out of the rad into the engine is too hot (assuming there's a separate switch for it somewhere, and depending on where it is). So if the circulation is ok, then I would expect the thermostat to be fully open and the bottom hose to be hot before the fan kicks in. If it isn't, it either implies that the coolant isn't circulating (so not being forced through rad for whatever reason), or that the fan switch is faulty and the fan is kicking in too early. It would be worth finding out where the fan switch is, and seeing whether that place is hot when the fan comes on.

Although the fan kicking in early wouldn't do much harm - the thermostat would close a bit to allow for the fact the rad is doing more cooling than before, and everything else should behave as normal.

Does the car ever overheat according to the temperature gauge? If the coolant isn't flowing through the rad, then the rad fan won't help cool it much, and I'd expect the temperature gauge to start to rise whilst the fan doesn't do much.

EDIT Having reread your original post:
OK it does creep above 90 degrees someimes. That implies circulation problem rather than fan coming on early. Or maybe head gasket as others have said causing exhaust gas to get into the coolant and heat it up more and/or introduce air locks.


the fan doesnt kick in early cause last time i heard it i checked the rad between the fan blades and it was hot, but it was only hot around the top hose, as if the rad was getting hot from the top hose first altho i couldn't really get to the other side of the rad to feel properly
sometimes it does creep up when you welly it on a fast road , but i tried that just today and it didnt do it because it has been actin half normal today but days when heaters are hot and cold and bottom hose cold it occasionally rises over 90 on a fast road, which most people would suggest head gasket so im scared

[FLENG2008]

Have to say hissing from tank after long run does sound a bit like head gasket. Once the coolant is all up to temperature, so has finished expanding, then whatever is coming out of the header tank must be coming from somewhere. If the car is actually boiling at that point, then coolant could be turning into steam (which is lots bigger), so the steam could hiss out. Or, if exhaust gasses are getting into the coolant (eg head gasket), then they will have to come out somewhere, and that will be through the header tank cap which has a pressure release valve in it...


yer i know exaclty what you mean but some days it doesn't do it

somedays it acts half normal holds pressure and get some heat no hissin

really strange probably head gasket

[FLENG2008]

right the block test was another one of those blue fliud tester thingys
but it didnt work mechanic said it can be radiator or head gasket
and i dont think its the rad cause when you squeeze the bottom hose you can feel the pressure in the top hose coming through the rad, so its not blocked and the hot water isnt getting to the rad so im thinking head gasket

i tho block test was a test to check pressure in the cylinders to check for loss of pressure through the gasket and if it is a head hasket fault why wont it show on a sniffer test??

thanks for everyones replies very helpful
thankyou

[zollaf]

the blue fluid tester goes in the cooling system filler and turns green/yellow if carbon monoxide is present in the cooling system. these work 100% on petrol engines, but not on diesels. in fact, ive never seen one change colour on a diesel, even though gas was definately leaking into the cooling system.

[p4dyk]

Hi all,

I also have a 02 GOLF TDi PD ATD engine code. Yesterday when driving I noticed that my temperature went over the 90 mark on thhe gauge. This only happened as others have suggested when driving hard, when driving casually 40-50mph the temperature droped to 90 and stayed there.

My top hoses coming from my rad to the n/s of the engine gets hot, however the hoses that comes from the engine to the bottom of the Rad does not seem to heat up. The heaters only warm up when driving hard and are cold otherwise. I took my thermostat out yesterday and this has now stopped the overheating the heaters are freezing which I was told to expect. I have checked the hoses after removing the stat and they are still the same top hose hot bottom hose cold. The bottom hose connects to the rad and the Thermostat housing on the front of the engine block.

I have described my problem to a local garage and he seems to think this is the water pump as says never heard of head gaskets being a problem on Golfs. I had cambelt changed aroung 120k and car now has close to 156k on. With this in mind I think a cambelt change is due which I will do the water pump and stat as well. What do you think about the possibility of my problem being the HG and what is the best and most productive way of checking it.

[FLENG2008]

i wouldnt change the pump unless you are sure its failed

take off the return hose and see

[mystic.bertie]

having been thru all this with my AJM engine it sounds very much like the head gasket however i was getting a lot of pressure in my coolant system, once the head gasket was sorted therte was hardly any pressure in the system.

if you remove all hoses you can run a water hose thru the engine, heater matrix and rad and if it flows easily you know its not blocked, mines flowed thru easily so no blocks.

you can remove the stat and run it just to eliminate a faulty one

from what i remomber you had to run/ drive the car fast to get the fan on as sitting on tickover never made it kick in

and as a few guys have already said, i also found out thru research the AJM are notorious for head gasket problems

[jlaspire]

Just a question really! Does the top hose on the car get hard as rock? Ive got the same problem and spent the night trying to get the air out which again hasn't worked! It seems im getting a build up of pressure at the start of the radiator but nothing else around the car. This only happens when ive drove the car and nothing when just on idle! No over heating or anything! Garage on friday so will let you know if they found anything! Have you flushed the radiator?

[FLENG2008]

Just a question really! Does the top hose on the car get hard as rock? Ive got the same problem and spent the night trying to get the air out which again hasn't worked! It seems im getting a build up of pressure at the start of the radiator but nothing else around the car. This only happens when ive drove the car and nothing when just on idle! No over heating or anything! Garage on friday so will let you know if they found anything! Have you flushed the radiator?

not sure if this was pointed at me but mine doesnt go rock hard but the top hose does get the hottest while the boottom is only warm..

have you done your thermostat?

[jlaspire]

Sorry it was for you! Just new to this! Ive not changed the thermostat yet as not had the chance! Due in the garage on friday! If you take a look at my post on the A6 section "no heat" ive put a link on which i found which you may find helpful.

[FLENG2008]

i would go for thermostst first cheap simple option

[FLENG2008]

to anyone who's bothered i just had a proper block test (snap on that screw to expansion tank with pink/red fluid NOT blue) came up within 10 mins that head gasket is leaking gases into the coolant

[herby0001]

Ahh shucks. Sorry to hear that.

[jlaspire]

Sorry to hear that mate!

[FLENG2008]

thanks
yes im wounded but i always knew i could be strong possability, i was just hoping it wasn't..

i also heard parts and enginering costs are around £500 and the cheapest quote from decent independant for labour is £400 so far

[jlaspire]

Major pain before Christmas! £500 is that for a new head as well? I had a rebuild done on a 205 gti head a few years ago and it was only about £90 for all new cut valve seats,seals,pressure test and skim! Seems alot

[p4dyk]

Hi all,

Just to let you know, I have just had my Water pump, Cam belt and Thermostat. Seems to have done the trick heaters working, not overheating etc. When mechanic took out the Water Pump the plastic propella had come of hence the problem of onerheating.

[FLENG2008]

Major pain before Christmas! £500 is that for a new head as well? I had a rebuild done on a 205 gti head a few years ago and it was only about £90 for all new cut valve seats,seals,pressure test and skim! Seems alot

£500 just for parts and engineering costs


Hi all,

Just to let you know, I have just had my Water pump, Cam belt and Thermostat. Seems to have done the trick heaters working, not overheating etc. When mechanic took out the Water Pump the plastic propella had come of hence the problem of onerheating.

well you got lucky mate, glad it wasnt head gasket for you too..

[hnael]

Hi,

I am new to this forum so apology if this isn’t the right page to post my query. I have recently bought an Audi “A4 3.0 v6 quattro 51reg” and I seems to have a similar problem to the one your page is about.

Anyway, I need your advice please and here is what want wrong on the second day I got the car:

Temperature meter doesn’t work and its reading 50c all the time, then the onboard computer came up with oil level warning and there was steam coming out of the front left side of car.

So, I pulled over and check the oil after leaving the car for about 20 min. When I check the dip stick, it seemed that the engine had no oil and I had to top it up and the same with the coolant water, that was almost empty too.

When I took it to the Audi approved dealer, the first thing he checked is the water pump and he also plugged in the computer to see if the computer recorded any faults.

The computer came back with no faults so he decided to check the water circulation. To check the circulation he turned on the heater inside the car and waited for few seconds. The heater works and it was blowing hot air so he said the water pump is working, by the way throughout the test the diagnostic computer was reading 90c but the temperature meter was inside the car was 50c and it hasn’t move.

He then decided to check the radiator. So he reached for a probe with a temperature LCD screen. When he checked the right side of the radiator the LCD on the temperature probe was readying 90c but when he inserted the temperature probe to the left side of the radiator it was reading 42c "radiator is blocked".

The car has had camp ballet and water pump changed at 80000 miles according to the Audi service book. The car is now at the approved dealer to investigate further and I feel that I have made a mistake going for an Audi.

Please can you advice me on what to do or if you have any idea why 2001 reg car has this issue.

Thank you in advance and I look forward to hearing from you.

Merry Christmas and happy new year to all.

Regards,

Nael

[herby0001]

Well, it sounds like you've had a bit of bad luck. Did you give it a proper look over, test drive, physical RAC check before buying? I would go for an Audi any day, they are great cars, as are VW's. BUT, as with any car, it can be abused. If you're handing over a lot of money, it's worth paying £130 for some peace of mind. If you bought the car from a dealer, you'll have a minimum 3 month warranty, but they often have MANY exclusions. If private purchase, well...

From what you're saying, it sounds like the Audi garage has identified a blocked rad. Good news anyway. I'd be a bit worried about the loss of oil.

There is an Audi section. Perhaps re-post there and the Audi experts can assist you further.

[jamie--golf3]

having similar problem with my mk3 golf... shes a 1.9 diesel!heater doesnt work any more and the pipe going to the coolant reservoir blew off today and filled the engine bay with gren coolant and i have a fella coming down to look at the car midweek before he buys it!!!!!!!!!:zx11::zx11::zx11::mad:

[producedapples]

ended up being the thermostat

i was under the impression the thermostat was in the top of the top hose because the top hose got hot first
i didnt know until today it was in the bottom hose, i would of thought that anyone who knew that the thermostat was in the bottom hose would have pointed me in that direction first as the bottom hose only getting slightly warm at the top would have been a big indicator that the thermostat was blocked shut

so if your bottom hose doesn't get hot and your car overheats when going fast try your thermostat, it may not be water pump or head gasket like everyone assumes


Yes I found that out too!! chaaged mine about 8 weeks ago, took that plastic housing off the top right hand side of the head, thinking...***!!! its the pipe which runs below the fuel inj pump into the block on a non PD derv golf, my bottom hose still doesnt get hot now, but runs at 90C now

[FLENG2008]

anyone who has coolant circulation problems should get a proper sniffer test done, i had 2 of the crap blue sniffers tests and both came up with not gasses found, i tried a proper snap on one with pink/red fluid and it showed up straight away that gasses were leaking into the coolant

[liam walsh]

FLENG2008 , does this sound familiar , my 1996 a4 110 tdi runs perfect , starts no problem , temp stay at 90 all the time but no heaters, I've replaced the main rad , thermostat, coolant , flushed the system numerous times , if i bleed the coolant system for about 15 mins after, the heaters work perfect then the temp starts to drop and after a while they are non existant and wont return unless I bleed the heaters through the bleed hole on the supply pipe for the heater matrix.
Is this sounding like head gasket to you?

Cheers,

Liam.