Another ongoing cooling problem - Advice needed

[Noodleman]

Hi Guys,

I am looking for some advice here about an on going problem with my 1998 A4 1.9 TDI.

About 6 weeks ago I had the head gasget blow. This caused the oil to mix with the coolant, and gave me a froffy, orange foam in the cooling system, which then spent about 15 mins pouring out of the coolant reservoir via the cap/overflow.

I had the head gasget repaired, (new gasget/skimmed etc) and also had a new thermostat fitted. During the head gasget being fixed, the garage called me to say that the Radiator was also leaking. We agreed to try fixing it with some sealer instead of replacing it to keep the cost down.

I got my car back, and all was well for a couple of weeks, until the coolant started to disappear. At first, only a small amount, then it got worse as time went on. small amount being about 1/4th a litre, and worst so far was approx 10l required over 50 miles.

So, assuming the radiator was the problem, I then had this replaced.

I got my car back, and all was good again for about 2-3 days, and then coolant started to disappear again in the same manor, started off with just a top up now and then, and now results in needing a lot of fluid daily.

So, the car went back to the garage again, where they pressure tested the cooling system. It passed the test. They then re-tested the system with the engine hot, again it passed. so, we know that the radiator / reservoir etc is not leaking.

At this point in time, we also replaced the cap on the reservoir assuming it was letting fluids pass.

Today, whilst testing the car (60 mile round trip) i also lost coolant. in the first 30 miles, driving approx no more than 2000rpm it lost approx 1/2 litre.

The journey home I took some faster roads, and took the car up to 2500rpm / 2700rpm where possible. After a while I noticed the temperature guage creap up above its usual 90. I pulled over, expecting to find no coolant in the system thus the overheat. However, the reservoir was at least 3/4 full. So, with this in mind... I am wondering if the problem is the water pump. The car quickly returned to normal temp, 90 and I was able to drive it home, keeping the RPM reasonably low. It did not overheat again.

I am aware that the pump in the A4 is simply an impeller. Could it be that this is damaged and thus not able to pump the hot water from the engine. The water in the engine is then boiling, causing excess pressure and coolant to escape through the reservoir cap?

As a side note to the story which I am sure will fit into it somewhere is the heater. About 4 weeks before the head gasget died, the heater was not able to produce anywhere near its usual level of heat. This got better after the car was repaired, but nowhere near where it should be. I did read online that somebody who was having similar symptoms to myself foudn the problem caused by the water pump not having enough pressure to get the water into the heater block effeciently... does this sound right, or is it misguided guess work?

Ideally I am looking for peoples "best guesses" as to what the problem is likley to be?

Thanks in advance for any replies,

Alec.

[phil miller]

hi mate from what you have said it does sound like a water pump problem, do you know if the cylinder head was crack tested when it was skimmed? but if its passed to pressure tests then i wouldnt have thought the head was cracked, if i was you id have the water pump checked, one other thing tho, the impeller maybe tight on the water pump when its cold and as it gets up to temp it could go loose then so if in any doubt replace it bud

[Noodleman]

Thanks for the info.

I was informed that the cylinder head was inspected for cracks during the HG repair, and that nothing identified as cracked.

One of the ideas was it might be cracked, and that only be leaking when hot (slight expansion in metal when hot making crack appear). The idea behind compression testing this when hot was to check if this was an issue.

I forgot to add in my original post that I inspected the coolant, which didn't show any sign's of contamination. I was curious if maybe the HG repair was botched and still leaking.

Just to be on the safe side, I ordered a block testing kit today, which I can run without the garage knowing, just in case it shows a problem with the head again.

I have a gut feeling that it is likley to be the pump... I've spent a lot of time doing a lot of reading today, and seems that a few people have had similar problems to me :(

[phil miller]

Thanks for the info.


I have a gut feeling that it is likley to be the pump... I've spent a lot of time doing a lot of reading today, and seems that a few people have had similar problems to me :(

the first time i came across the water pump impeller problem it had been inspected by a garage who had said it was the HG i then carried out my tests and at the time was unsure, after an hour or so of doing other tests i was sure the HG was fine, so i checked the return flow to the header tank (seeing what was returning ) and there wasnt a return when the engine was at temp so i took the pump off but all seemed fine, i was getting ready to remove the head when i decided to put the pump in boiled water for 5 mins as sson as i checked it the impeller was spinning freely sence then ive replaced loads, now back to your car, it could very well be your W/pump impeller has come free when hot, over time this has damaged the rad which in turn blow the HG, i think the best thing to do is to check/replace the water pump just for piece of mind

[Noodleman]

the first time i came across the water pump impeller problem it had been inspected by a garage who had said it was the HG i then carried out my tests and at the time was unsure, after an hour or so of doing other tests i was sure the HG was fine, so i checked the return flow to the header tank (seeing what was returning ) and there wasnt a return when the engine was at temp so i took the pump off but all seemed fine, i was getting ready to remove the head when i decided to put the pump in boiled water for 5 mins as sson as i checked it the impeller was spinning freely sence then ive replaced loads, now back to your car, it could very well be your W/pump impeller has come free when hot, over time this has damaged the rad which in turn blow the HG, i think the best thing to do is to check/replace the water pump just for piece of mind

I agree. I intend to arrange for the pump to get replaced with the garage tomorrow.

The one thing that isn't clear, is if the pump wasn't pushing water through the cooling system,

would this cause loss of coolant at the levels I have been seeing?

Thanks,

Alec.

[phil miller]

I agree. I intend to arrange for the pump to get replaced with the garage tomorrow.

The one thing that isn't clear, is if the pump wasn't pushing water through the cooling system,

would this cause loss of coolant at the levels I have been seeing?

Thanks,

Alec.

it would cause the coolant to build up pressure and push it out of the header tank cap i would have thought, another thing to check if all is ok with the pump is to have the engine running and pressure test the coolantant system only leave it under pressure while the engines running and look for leaks or tell tale signs from hoses, exhaust and around all joints, the amount your losing the signs will show in about 5 mins of doing this, id still say its the pump tho bud

[Noodleman]

it would cause the coolant to build up pressure and push it out of the header tank cap i would have thought, another thing to check if all is ok with the pump is to have the engine running and pressure test the coolantant system only leave it under pressure while the engines running and look for leaks or tell tale signs from hoses, exhaust and around all joints, the amount your losing the signs will show in about 5 mins of doing this, id still say its the pump tho bud

Thanks for the info Phil.

I wasn't able to confirm 100% if the water was coming from the coolant cap today, because by the time I had gotten out of the car and lifted the hood it had stopped flowing, however there are signs that the it was coming from the box, with lots of water below.

do you know if adding antifreeze will reduce amount of steam/vapor that will come off of the water/coolant? Oddly, when the system has antifreeze in it, the problem is not as bad. It still happens, just slower. After topping up several times with just water, and the antifreeze is less concentrated, it seems to spaff itself more frequently.

I was wondering it this could be the reason for the issue starting off not so bad, and getting worse.

Trying to find some logic to it :)

[ike]

Antifreeze raises the boiling point.

[Noodleman]

Antifreeze raises the boiling point.

I thought it did too, but was told by a garage that it didn't do that. If it does, it also fits with my theory about the coolant leaking quicker when there is less or no antifreeze in the system, because it is boiling off quicker thus more pressure sooner...

[phil miller]

Antifreeze raises the boiling point.

what rise's the boiling point is the coolant is under pressure, nothing to do with antifreeze


I thought it did too, but was told by a garage that it didn't do that. If it does, it also fits with my theory about the coolant leaking quicker when there is less or no antifreeze in the system, because it is boiling off quicker thus more pressure sooner...

Normally when you have anti freeze in the coolant it will leak faster, not know why but its fairly well known that anti freeze will find a way out if there is a slight leak, modern anti freeze does alot more than it use to ie 15 yrs ago it lowered the point at which the coolant froze, nowadays it does that but also, lubs the water pump, stops corrosion and transfurs heat better now

[ike]

Originally Posted by ike
"Antifreeze raises the boiling point."

what rise's the boiling point is the coolant is under pressure, nothing to do with antifreeze.

To be exact, the antifreeze raises the boiling point IN ADDITION to the increase in boiling point through increased pressure. At 50% antifreeze the boiling point is raised to 106 degrees C. At 70% antifreeze content, the boiling point is 113 degrees C. The boiling point is then increased further with increasing pressure. The mixture also has a higher specific heat capacity i.e. the coolant can more efficiently transfer heat. That's one important reason to use 'G' spec. coolant.

[Noodleman]

Hey guys,

After talking with the garage again today, they are of the impression that there must be "some kind of crack somewhere within the engine"

They have flushed the system again, put in another new thermostat in case the last new one was faulty, given the car a long road test, but the car is still loosing coolant, and brings up the warning light about the low levels/temp.

They have said that there isn't much else they can do apart from testing for cracks, which is an expensive & time consuming process.

i've started car hunting!

[zollaf]

so have you had a new water pump ? is it loosing coolant because its overheating, or overheating because its loosing coolant ?

[Noodleman]

so have you had a new water pump ? is it loosing coolant because its overheating, or overheating because its loosing coolant ?

No, the water pump did not get replaced because the garage are 100% sure it isn't the issue because if it was the pump, the car would overheat then dump its water, rather than dump the water then overheat.

Sound logical?

[steve320cd]

Thanks for the info.

I was informed that the cylinder head was inspected for cracks during the HG repair, and that nothing identified as cracked.

One of the ideas was it might be cracked, and that only be leaking when hot (slight expansion in metal when hot making crack appear). The idea behind compression testing this when hot was to check if this was an issue.

I forgot to add in my original post that I inspected the coolant, which didn't show any sign's of contamination. I was curious if maybe the HG repair was botched and still leaking.

Just to be on the safe side, I ordered a block testing kit today, which I can run without the garage knowing, just in case it shows a problem with the head again.

I have a gut feeling that it is likley to be the pump... I've spent a lot of time doing a lot of reading today, and seems that a few people have had similar problems to me :(

Hi, my 98 tdi 110bhp A4 overheats like yours does or did, the engine is boiling and the radiator is cold and this forces the boiling water out of the header tank. Have you had the water pump replaced? If so did it fix the problem?. Did you also get a loud clicking noise when you turn but more so when pulling out of a junction turning left or right? My car has been making this loud clicking noise for months now and has got worse and worse and now the engine overheats if i go above 45mph ( a problem as i travel to work via a motorway!) I had the timing belt replaced and my m8 said the clicking could be the fan belt tensioner so he replaced that for me but the clicking noise stayed so im wondering if its the water pump making the clicking noise? I would appreciate your opinion please.
Thanks
Steve

[yaman]

Did you also get a loud clicking noise when you turn but more so when pulling out of a junction turning left or right? My car has been making this loud clicking noise for months now and has got worse and worse
Steve

Are you sure this clicking while turning is not worn CV joints?

Regards
Jim

[Noodleman]

After checking the paperwork before i got rid of the car, i found the water pump was replaced when the belts were done, which was not that long ago, fairly sure it wasn't the pump in this instance.