divil

'89 951...This morning I noticed my coolant was a little below the minimum mark. I topped it up and went for a drive.

When I got back I left the car idling for a minute or less, and when I came to switch it off, it was overheating...the needle was in the red. Just the beginning of the red, and it can't have been there for very long.

Then I saw coolant leaking out of the bottom on the driver's side. It seemed to be coming from underneath the coolant tank. The thing is, the leak stopped after a minute or so and the coolant level was back roughly to where it was this morning. I tried topping it up, but there was no sign of the leak coming back. I filled it all the way to the maximum and left the car to cool down, then started it again. So I presume it was overflowing?

I ran it for a few minutes, till the temp stabilized (gauge about 3/4 of the way up). Let it run like that for 5 minutes or so. No sign of overheating, no leak - not a drop.

Any ideas? So did the overheating cause the overflow, or would it be the other way around? It was a warm day and the car was running nice and hot.

arthropraxis

The leak is probably the overflow. Have you checked the fans operation? There are several things to look for, the coolant tank cap for one. If the seal isn't thigh enough to hold pressure the water boils at a lower temp.

divil

At least one of the fans was on when I first switched off the engine, when I noticed the overheating. It stopped if I removed the key though so I left that in until the fan stopped by itself. I wasn't 100% sure if this is right, I would have thought it should keep running even without the key? Anyway I didn't notice if both fans were on, I'll run it again tomorrow and check that.

As regards the tank cap...it looked normal to me. How do I check if there is something up with it?

arthropraxis

The cap seal is rubber and degrades over time, you should be able to tell by how it looks. I am throwing out the easy stuff to check. The fans should both be on at one time in low or high speed. The tempostat on the radiator that triggers the fans could be gone. There is a good writeup on Clarks-garage.com to check that.

divil

Thanks. I checked the coolant cap and it really looks fine. No signs of degradation in it at all really. I noticed today the coolant level is down a bit lower than where I topped it up to yesterday, but it's raining today so I can't tell if there has been a leak. I just ran the engine for 20 minutes and it didn't overheat. The fans were running on high any time the temp got near the top mark.

So I am still trying to figure out why I had overheating and overflow yesterday - what connects the two?

One thing I am not sure about...after idling for a while I drove a short distance and then stopped and let it idle again. The needle moved towards the top white mark, but if I revved the engine gently, it quickly moved back down to about the halfway mark. Why is that? Is it because the water is being pumped faster?

Leonel

I had a kind of similar problem, had it pressure tested and it turned out the radiator had a tiny little crack