timp928

Hi,

I have an issue with my 1990 S4 which I have had for 4 years, and have completed numerous maintenance jobs on (Inlet manifold refresh, timing belt etc etc you know the drill). I have enjoyed reading this forum, but do not post often.

My car has an Aluminium radiator built by a respected radiator builder that I installed 2 years ago (with a full cooling system refresh - thermostat, all hoses, o-rings, gaskets etc) . At the same time I also also replaced the plastic expansion tank with an aluminium one from the same manufacturer, with a different radiator cap (supplied with the tank). I have done 20,000+ enjoyable Kms since then.

The other day while driving (sedately) the coolant light came on, shortly followed by white vapour from under the bonnet. On inspection the radiator was leaking from the cores and the fans were distributing coolant over the engine - creating the white vapour. I topped up the coolant, waited for the peak hour traffic to subside then drove home.

My temp gauge runs about 1mm below the white line normally, at no time did the temp go above the white line, and there was no over-temperature alarm.

When I removed the radiator, coolant stains on the aluminium in 2 places were evident. (see attached Pic)

I returned the radiator to the manufacturer and they attempted repairs.
They reported back that the radiator was not repairable, as the end tanks had ballooned (see attached pic) , a few of the welds had cracked, as well as several leaks in the cores, and they found traces of oil in the radiator!!

They suspect that my car has blown a head gasket and this has damaged the radiator!!

I am shocked - I had no indication that anything was wrong with the vehicle, and now with the radiator out - I am like an animal caught in the headlights, don't know which way to turn!

The coolant was always maintained at 30%, I have the oil analysed every change, routinely check the block etc for oil leaks/ weeps etc - this is a well (over) maintained vehicle.

The oil in the dipstick is clear (recently changed) and under the oil filler cap is normal, water in the oil was ok less that 500kms ago: (Water (% by FTIR) <0.1), the exhaust is black.

Surely the head-gasket would have blown a radiator hose off, or the temperature sensor out before damaging the radiator?

My concern is that if I pay for a new radiator and install it - it may blow again due to an issue with the car!!
The the other side is - perhaps the radiator was faulty somehow.?

My questions to the forum are:
How can I check for a head gasket leak, without installing a radiator?
Am I chasing ghosts, or is it likely I have done a head gasket?
Could something else have caused the radiator to fail - perhaps the ATF cooler?
What further checks should I make of the radiator?

Looking forward to an enlightening discussion :-)

regards
TheTimp
90 S4
Black on Black

blown 87

Yes, I have seen a few different makes of cars blow the end tanks off on plastic end type tanks.

Find a shop that can do a chemical test for the presence of cumbustion chamber gasses.

jackson101

yes, and heater box/core also!

JHowell37

They're trying to weasel out of honoring the warranty on your radiator(if there is one.) There's been nothing else you've mentioned at this point that should indicate anything other then a faulty radiator. I don't think you have a bad head gasket, I think it's a bad radiator, plain and simple. If your car exhibited no overheating characteristics prior to the failure of the radiator, and your car didn't overheat when the radiator did fail, then I doubt it's a problem in the engine. I'd also like to see proof of engine oil in the radiator.

If this company really wanted to stand behind their product, they'd provide you with a replacement to see if you can replicate the problem. But they're just making up some BS so they can wash their hands of it.

86'928S MeteorGrey

Can't a compression test identify a blown head gasket?

86'928S MeteorGrey

You can also do a pressure test for the oil cooler leaking into the radiator. The oil pressure would be high enough to explode the end tank.....

JHowell37

If a high enough volume of oil entered the radiator to cause enough pressure to explode an end tank, I think there would be many other problems with the engine. Plus you'd need to dump in enough oil to raise the pressure of the entire cooling system high enough to start causing damage. I suppose anything is possible, but what is most likely is that the radiator was of dubious quality to begin with (I noticed a few scorch marks around the welds) and it failed. As I said earlier, the radiator shop is trying to weasel out of any responsibility here.

James Bailey

The radiator cap is the "fuse" it is designed to relieve any excess pressure. Maybe it failed to vent but not likely. You can loop the two radiator hoses together with a short piece of pipe and loop the trans oil cooler lines needs fittings or use the cooler out of the bad rad. and start the car and run it a bit to see what is happening as it warms up.

timp928

Thanks guys, I appreciate the quick response. I am pretty handy with the tools - but not a trained mechanic.

The Oil on the dipstick is not low, so if any oil has got into the coolant it would have to be less than 0.5 of a litre..

Chatting with some guys down under, we presumed the ATF lines would not be under much more than atmospheric pressure - have we got it wrong?
The radiator people are saying that the ATF cooler was not leaking..

So to summarise I should:
Compression test, get the coolant examined for combustion gases, and test the radiator cap..

I am interested in what you are saying James:
>run it a bit to see what is happening as it warms up.
I can connect up the radiator/ ATF lines without too much effort - but what should I look for?

Should I run it till the expansion tank cap vents, while looking for white smoke out the back? Is there a more "specific" test?

I am concerned that running the engine may cause more damage(?) - I have seen coolant in a cylinder crack the bore - I would prefer not to go down that path !

regards
TheTimp
90 S4
Black on Black

JHowell37

I just went and looked at your pic. I forgot that you've got an external engine oil cooler. There's really no possible way for engine oil to get inside the radiator on your car. If your ATF cooler was leaking it would dump a lot of ATF into the radiator quickly. And you would have seen it when you drained the coolant.

I really don't see a point in going through all of these tests on your engine. No offense, but you have a cobbled together radiator of dubious quality. That's the weak link. Did your car overheat at all? From what you said, it didn't even overheat when it started leaking. My own experience has shown me that you can probably lose about 30%-40% of your coolant before things start getting too hot. Even then if you can keep the car moving, you can probably get it home safely.

What I would do is source another radiator, put it in, drive the car down to their facility and let them see that your engine is fine. Then you can promptly remind them that most businesses live and die by word of mouth, and that you're not a happy customer.

timp928

>No offense, but you have a cobbled together radiator of dubious quality.
None taken, in fact that was my initial view, when it failed.

>Did your car overheat at all?
No, once the coolant alarm went off I pulled into a service station, let it cool down a bit, then topped up the coolant. I only had to do that once to get home. So twice in total - once when the problem appeared, and once more on the way home.

>If your ATF cooler was leaking it would dump a lot of ATF into the radiator quickly. And you would have seen it when you drained the coolant.
The coolant looked great - vibrant green - though I didn't see what leaked out on the road initially..but can assume it would have been the same.

But nagging doubt has taken hold , and it will take a couple of weeks to get hold of a replacement radiator - so I might as well do some checks in the interim. (I have pre-paid Oil/ Coolant Test kits on hand)

Funny (not really) I am almost due for the periodic 20,000 service, so coolant was due to be replaced-but I thought I could have kept the radiator!!!

>Then you can promptly remind them that most businesses live and die by word of mouth, and that you're not a happy customer.

Been mentioning that on the phone already!


regards
TheTimp
90 S4
Black on Black

Charles Parkinson

Hi Timp,
That's a real bummer but I reckon it is a radiator/cap/expansion tank issue as I've had boosted motors (not 928) eat head gaskets on track before and even then the radiator cap was able to vent the pressure fast enough to avoid damage to the radiators.
I'd be tempted to test the radiator cap and see what pressure it starts venting at which should be relatively easy and will answer one question. I would also be interested to know how much pressure would be needed to baloon the end tanks like that - any engineers got suggestions ?(Might be worth posting on landshark as I seem to remember Steve L from WA is an engineer who works with pumps / pressure vessels etc). Could be that the material for the end tanks are not up to the task and has balooned & fatigued over time which has led to the leaks.
I've got a spare "old" S4 radiator here in Sydney if you're desperate.
Cheers, Charles.

Lizard928

If you got a replacement expansion tank with cap from them too and they are saying this is due to excessive pressure then they have sunk their own boat. The rad cap can vent a TON of air/pressure fast.

The reason the tanks ballooned is because the material used to make the end tanks was too thin, this is also shown by there being leaks at the welds. In my opinion I would not take no for an answer and I would DEMAND a replacement or full money back. Them saying this was caused by a bad head gasket is a flat out lie.

fraggle

If the head gasket failed this badly a simple compression test would reveal the problem.

S4ordie

To me it seems the hoses would have blown off befor those radiator tanks would have bulged like that. I can't say specifically how much pressure it would take, but even a very thin aluminum tank should take a lot. Certainly more than the hoses on the engine.

I think the shop purposely over pressurized the tank and made it swell like that to get out of replacing it.