[Jono]

I have a similar problem to Cosimo....except no puddle under the car. I was driving my son to a birthday party last Sunday when the warning lignt came on and the temp needle hit the red. Pulled over and left it for a few hours before limping home after topping up the radiator.



I've teken the car out for a couple of 30 minute runs since then and found I'm losing about a half litre (approx 1 pint) of coolant each time - no puddles on the garage floor, no white smoke on start-up and the engine oil looks clean and not milky so I'm thinking it's not a head gasket problem.



What could it be? A quick sarch of the forum reveals many causes of overheating but nothing about vaporizing coolant! I'm guessing maybe a radiator hose that fails under pressure since there's no loss of cooland while sitting in the garage. Thoughts?



TIA!

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[SILVY968]

Sounds like a bad water pump. The coolant will overheat and spit out of the overflow tube while driving, maybe not in the garage.

Also could be the far less expensive thermostat stuck in the closed position. If it turns out to be the thermostat I would drill a small hole in the thermostat to allow coolant to run through even if it gets stuck closed. You may also be able to get a new thermostat that remains open when broken instead of closed.

Be very careful running these engines hot, aluminum heads do not like this and will cause damage if allowed to run in a heated condition.



If this happens again turn on the heater, it will run the coolant through the heater core and help a bit...its better that nothing.

Brian

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[Georges]

I had a problem test driving a 968 years back. The temp went up and I stopped to check the coolant level. A bit low but not enough to explain. I let cool and try again. Temp is up and I check for leaks etc. and notice the coolant level is lower. On the third check the car definitely needs coolant. So I try to limp back to the dealer wondering where the coolant is going when there's no leak. On one of my stops to refil I happen to open the hood when the HCV is spraying steam. I notice that when it stops spraying everything is dry because of the engine heat. I let it sit and watch and the HCV sprays steam at interval. Mystery solved that day.



The benefit is I had the car for a lot longer than I expected. On most of my stops folks would come over and comliment on the car.

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[flash]

it has to be going somewhere



if there are no signs of leakage, you could have a head gasket issue - it is not an automatic given that coolant gets into the oil - if it is just getting into the combustion chamber, it will just burn off



pull the plugs and take a look



do a compression check - a coolant leak in the combustion chamber will usually show up as an increase in compression in a cylinder



sniff around the tailpipe when it is running - you should also smell something like maple syrup if you have coolant in there

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[Jono]

Thanks everyone, it seems the usual suspects are at play here, HCV, waterpump, thermosstat, head gasket.....I'll do some more troubleshooting - what's the most likely culprit do you think? The car's done 64k miles and no a/c. We've owned the car 5-6 years with absolutely no cooling problems in that time and the temp gauge rarely gets past the bottom mark (8-oclock).

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[unknown4u]

Hi Jono, your car does not hit almost the 10 o"clock mark in heavy traffic?

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[Jono]

[quote name='unknown4u' post='48009' date='Feb 23 2008, 11:19 PM']Hi Jono, your car does not hit almost the 10 o"clock mark in heavy traffic?[/quote]



No, it's never hit 10 - well not until last Sunday anyway! It's normally around 8-8.30 which seems lower than a lot of other people on the forum. We have a pretty temperate climate here between about 8-28C (about 46-82F) which might help it run cooler. No a/c either, not sure if that makes a difference.

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[flash]

clean the engine and look for leaks - that coolant has to be going somewhere - if it isn't leaking out, it's leaking in

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[sp4149]

[quote name='Jono' post='47926' date='Feb 21 2008, 07:28 PM']I have a similar problem to Cosimo....except no puddle under the car. I was driving my son to a birthday party last Sunday when the warning lignt came on and the temp needle hit the red. Pulled over and left it for a few hours before limping home after topping up the radiator.



I've teken the car out for a couple of 30 minute runs since then and found I'm losing about a half litre (approx 1 pint) of coolant each time - no puddles on the garage floor, no white smoke on start-up and the engine oil looks clean and not milky so I'm thinking it's not a head gasket problem.



What could it be? A quick sarch of the forum reveals many causes of overheating but nothing about vaporizing coolant! I'm guessing maybe a radiator hose that fails under pressure since there's no loss of cooland while sitting in the garage. Thoughts?



TIA![/quote]

Jono,

Sounds pretty much exactly what happened to our 95 Cab three years ago. Sudden overheating, Using coolant, but not leaking, no coolant on the floor, no coolant in oil and no oil in coolant. After trying to trouble shoot the problem for six+ weeks, finally got white smoke on start-up. It was the head gasket. There were a lot of posts about it on the old 968.net forum.

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[Jono]

[quote name='sp4149' post='48401' date='Feb 29 2008, 12:35 PM']Jono,

Sounds pretty much exactly what happened to our 95 Cab three years ago. Sudden overheating, Using coolant, but not leaking, no coolant on the floor, no coolant in oil and no oil in coolant. After trying to trouble shoot the problem for six+ weeks, finally got white smoke on start-up. It was the head gasket. There were a lot of posts about it on the old 968.net forum.[/quote]



Thanks sp4149, that sounds exactly like what we're experiencing. I was about to embark on the troubleshooting process this weekend but it looks like the head gasket is the prime candidate, I'll check again to see if we're getting white smoke on startup. Funny you should mention 968.net - I haven't been there for ages but checked it out to see if they has any info only to find the forums out-of-order.

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[flash]

unfortunately i too suspected the head gasket - handle it before it warps the head, or worse, cracks it



.net has been down for many weeks - likely permanent

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[Jono]

So it's been a while since I started this thread and it's about time I finished it off. It transpires that I had two cooling problems:

1) Radiator fans coming on intermittantly - replacing the thermoswitch fixed that. I originally thought the radiator fan relay was causing the problem (I've had to replace several relays) and almost replaced the fan relay before deciding to change the thermoswitch instead....good thing I did because the relay (a custom Bosch unit) is heinously expensive. The thermoswitches come in a variety of different temperatures, I can't recall whcih one I got but have found that the fans now start much later when the engine is hotter - around 10-oclock (under the red) rather than the 8.30-9.00 that it used to. No problems though, it still operates in a consistent manner. I'll look at changing the thermoswitch for one that comes on earlier in the future.

2) The 'missing coolant' problem was caused by the plastic end cap (for want of a better description - see http://www.968forums.com/index.php?showtopic=6619) on the end of the water pump held by two hex bolts. The o-ring had failed which I replaced but didn't help as the plastic assembly had warped slightly, so I replaced the entire plastic unit including o-ring for about USD12. At standstill the o-ring was weeping slightly and I suspect it was leaking a lot worse when the system was under pressure and goes some way to explaining why I was losing coolant for no apparent reason. Thankfully it wasn't the head gasket as I had feared!

I also changed the heater control valve for the heck of it since it has also been known to fail but I needn't have bothered. Still it's one less thing to worry about.

On the road again!

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