2002 Audi A4 1.9tdi overheating?

goodstuff!

As above. When the car comes under load (pulling trailer) It rises in temperature rapidly.
Sometimes on short journey's the temperature stays normal but when its parked up after, water comes out from the expansion tank (under cap).
The electric fan seems to come on at unusual times, like when you start up from cold!
Can anyone shed any light on this?
Please don't say head gasket is gone, but if it is, what would be a definite giveaway?
Cheers.

goodstuff!

Anyone?

Nissan doctor

Very difficult to say without seeing it, several things could cause overheating. I presume you've checked the coolant level?

Tea drinker

Is the fan on when it's overheating> and it's pushing air the right direction ;-) ?

Might be a thermostat, assuming other things ok.
Maybe a flush of the cooling system would do no harm, apart from the hit on your wallet for coolant, but you could get that done when changing the thermostat

goodstuff!

goodstuff! wrote: »

As above. When the car comes under load (pulling trailer) It rises in temperature rapidly. .............

What about when it's not pulling a trailor? How long has it been like this?

goodstuff!

Coolant level is ok. I'm not sure about the fan being on when its overheating because i refuse to tow a trailer since it happened. But the coolant coming out under the cap when its cool is the main headache.
There was a new thermostat fitted and system flushed.
I'm baffled but all the problems must be connected some way!

goodstuff!

goodstuff! wrote: »

Coolant level is ok. I'm not sure about the fan being on when its overheating because i refuse to tow a trailer since it happened. But the coolant coming out under the cap when its cool is the main headache.
There was a new thermostat fitted and system flushed.
I'm baffled but all the problems must be connected some way!

Can we deduce from that post that the following is the story
- overheated while pulling a trailer
- mechanic reckoned stat was the fault so replaced it and flushed the system
- since then (or an unknown time since) the coolant system has been overpressured

???

goodstuff!

RoverJames wrote: »

What about when it's not pulling a trailor? How long has it been like this?

It showed no sign of any problems until i towed a trailer about 6 months ago. Showed no signs of any problems after towing the trailer, but changed the stat anyway. There was no problems again until i towed a trailer 2 weeks ago, it overheated again and since then all the rest of the problems occoured.

Nissan doctor

If a headgasket is failing it will show up initially when the engine is under most load, ie pulling a trailer.

You say it also pressurised when cold, this is also a sign as when the engine warms up it expands and will, partially at lest, conseal a leak.

You need to have a sniff test and leakdown test done to confirm.

goodstuff!

Cheers men, looking like a head gasket so! I was informed that the metal head gasket never goes on these, but i suppose there's always a first!

Nissan doctor

goodstuff! wrote: »

Cheers men, looking like a head gasket so! I was informed that the metal head gasket never goes on these, but i suppose there's always a first!

Any headgasket can fail, its usually made worse by other problems like poor quality coolant or topping up with normal water, low coolant or, whick might be your issue, excessive load on the engine.

What sort of trailer are we talking about?

goodstuff!

Nissan doctor wrote: »

Any headgasket can fail, its usually made worse by other problems like poor quality coolant or topping up with normal water, low coolant or, whick might be your issue, excessive load on the engine.

What sort of trailer are we talking about?

Car transporter with car on top! It was heavy alright.
How much wuold you say im looking at to get the gasket done?

Antikythera

I don't see how a blown head gasket would cause excessive coolant pressure.

Do these cars have electronically controlled coolant systems? If so, I would look there.

Nissan doctor

Antikythera wrote: »

I don't see how a blown head gasket would cause excessive coolant pressure.

Do these cars have electronically controlled coolant systems? If so, I would look there.

I'd advise some research on head gaskets and cooling systems so....

Tea drinker

Nissan doctor wrote: »

I'd advise some research on head gaskets and cooling systems so....

Aye, the high pressure from within the combustion chamber leaks past the faulty head gasket into the cooling system.

As the cylinder head needs cooling - coolant must go from the cylinder block passages to holes in the head.
As oil is needed for lubrication... same thing.
The head gasket has holes to allow the oil and water to flow to/ from the block into the head, and keep the fluids separate, all the while containing the mad pressure of the combustion chamber.

When the head gasket fails, several things can happen, the combustion pressure leaks into the cooling system and water loss and overheating result. Oil can get into the water resulting in "mayonaise" in your engine... look for it under the oil filler cap.
Water can leak into the combustion chamber and result in a sad day for the engine.

Sounds like the gasket is on the way out, maybe a pressure test or coolant test could show for sure. Check for mayonaise as well...

goodstuff!

Tea drinker wrote: »

Aye, the high pressure from within the combustion chamber leaks past the faulty head gasket into the cooling system.

As the cylinder head needs cooling - coolant must go from the cylinder block passages to holes in the head.
As oil is needed for lubrication... same thing.
The head gasket has holes to allow the oil and water to flow to/ from the block into the head, and keep the fluids separate, all the while containing the mad pressure of the combustion chamber.

When the head gasket fails, several things can happen, the combustion pressure leaks into the cooling system and water loss and overheating result. Oil can get into the water resulting in "mayonaise" in your engine... look for it under the oil filler cap.
Water can leak into the combustion chamber and result in a sad day for the engine.

Sounds like the gasket is on the way out, maybe a pressure test or coolant test could show for sure. Check for mayonaise as well...

No, there's no oil/water mix as yet, that's what has me so confused!

Antikythera

Nissan doctor wrote: »

I'd advise some research on head gaskets and cooling systems so....

And I would advise you to do some research into coolant control modules. [so...]

Antikythera

goodstuff! wrote: »

No, there's no oil/water mix as yet, that's what has me so confused!

Find out what's controlling your radiator fan. Seems to me like the excessive coolant pressure is due to fan not doing its job properly.

Stoolbend

Does that model a4 have an electric cooling fan?

It's possible that the impeller on the water is starting to come loose and can't pump enough coolant.

goodstuff!

barry81 wrote: »

Does that model a4 have an electric cooling fan?

It's possible that the impeller on the water is starting to come loose and can't pump enough coolant.

No, she got a new water pump about 10k miles ago. It has a pully fan and an electric fan alright Barry.

Antikythera

goodstuff! wrote: »

The electric fan seems to come on at unusual times, like when you start up from cold!

Your fan is controlled by something like this:

http://www.iboldesign.com/store/99-00-01-02-03-vw-jetta-passat-bettle-audi-a4-fan-relay-module-1j0919506k-898972000/

These are not indestructible unfortunately.

johnayo

As Paint Doctor said early in the thread, too many possibilities without seeing the car.
It sounds to me that the rad core is blocked. That would answer the overheating while the engine is under pressure towing the trailer. Although it doesn't answer the fan coming on when the engine is cold.
I am aware you said you had the system flushed, but it can be extremely difficult to clear a blocked rad core.

johndaman66

goodstuff! wrote: »

No, there's no oil/water mix as yet, that's what has me so confused!

Need not always be the case though. I've had a head gasket go on me once and there was no oil whatsoever mixing with coolant. Coolant was seeping into the combustion chamber alright. If I had left the car sitting for a while it would run pretty roughly for a while so guess that was because a considerable drop of coolant had seeped into combustion chamber. I was actually driving around for quite a while before I got it repaired. At first it was only taking about a cupful of coolant every 3-400 miles but by the time I got the head gasket repaired it was using up to a jug full of coolant every 50 miles or so. Coolant was being blown out the exhaust which actually made sense.

Now I have had a few other cars with headgaskets go on me (they are a favourite of mine) and in each of them cases I was getting the usual oil mixing with coolant symptoms but as afore mentioned need not always be the case...

Nissan doctor

Antikythera wrote: »

And I would advise you to do some research into coolant control modules. [so...]

So, in your experience, how would the rad fan not working correctly cause the cooling system to pressureise when cold?

Antikythera

Nissan doctor wrote: »

So, in your experience, how would the rad fan not working correctly cause the cooling system to pressureise when cold?

Just trying to help OP.

Being a hobbyist, I haven't done many head gaskets, but I've done a few.

The last one I did, on completion of the work, the rad fan would start when the engine was cold and then cut out. When the engine was up to temp, the fan wouldn't cut in at all and this would result in overheating, thus excessive pressure in the cooling system (obviously).

After much head scratching and research, I was led to the coolant control module which sits in the front wing directly below the wash-wipe reservoir and the expansion tank (design fault?):rolleyes: On opening this up it resembled something that had been on the sea-bed rusting for a good while.

On changing the ccm for one found at a scrapyard all was rosy in the orchard.

In his opening post, OP comments that the fan cuts in at random times. This is why if I was a betting man I would wager his problem stems from whatever is controlling his radiator fan. I don't know this particular engine, but if I had to do the work, I would soon learn.

-Corkie-

Seems very complicated OP. I dont suppose you got the car scanned for fault codes. It may show up a broken sensor??

Antikythera

Nissan doctor wrote: »

So, in your experience, how would the rad fan not working correctly cause the cooling system to pressureise when cold?

Also... good question!

I wonder if OP meant 'cooling' as opposed to 'cool' when he mentioned coolant leaking from cap?

Will be interesting to hear results when (if?) he comes back.

Antikythera

Tea drinker wrote: »

Aye, the high pressure from within the combustion chamber leaks past the faulty head gasket into the cooling system.

As the cylinder head needs cooling - coolant must go from the cylinder block passages to holes in the head.
As oil is needed for lubrication... same thing.
The head gasket has holes to allow the oil and water to flow to/ from the block into the head, and keep the fluids separate, all the while containing the mad pressure of the combustion chamber.

When the head gasket fails, several things can happen, the combustion pressure leaks into the cooling system and water loss and overheating result. Oil can get into the water resulting in "mayonaise" in your engine... look for it under the oil filler cap.
Water can leak into the combustion chamber and result in a sad day for the engine.

Sounds like the gasket is on the way out, maybe a pressure test or coolant test could show for sure. Check for mayonaise as well...

Makes logical sense. Good post.

Tea drinker

Antikythera wrote: »

... was led to the coolant control module which sits in the front wing directly below the wash-wipe reservoir and the expansion tank (design fault?):rolleyes: On opening this up it resembled something that had been on the sea-bed rusting for a good while.

On changing the ccm for one found at a scrapyard all was rosy in the orchard.

interesting fault.........

would be some pain in the hole if the OP's new pump was faulty, I've heard some of the VW ones the impeller can spin on the shaft, or fins break.
Replacement ones are usually metal and less susceptable to this fault though.

Antikythera

Tea drinker wrote: »

interesting fault.........

would be some pain in the hole if the OP's new pump was faulty, I've heard some of the VW ones the impeller can spin on the shaft, or fins break.
Replacement ones are usually metal and less susceptable to this fault though.

Vauxhall Astra... Wasn't mine, honest:D

Coolant control module gathers information from temp sensor, among other sources, and sends signals to rad fan and aircon systems.