Over Heated Once But Hasn't Since

[DanRM 0 1 Cars]

I was driving to work last month when we had the 1st lot of real cold weather and i got about 9 miles before my 205 1.6 gti over heated to the point that the lights came on.

 

I checked the water and there was nothing in there (topped up 2 days before when i added more anti freeze). It hasnt lost water like that before nor since this happened. So I filled it up and came home with the expansion tank cap off. checked all pipes and places i can think of that may be leaking when i got home that night but could find nothing.

I have had the car off the road since then but finally got round having a better look at it this afternoon.

 

 

I drained the water and filled it back up 50:50 antifreeze bled the system and seemed fine, no leaks after running it at 3000rpm then left the car ticking over for half hour keeping an eye on the gauge and it went 3/4 of the way up before the fan kicked in and stayed around that temp.

 

I haven't been able to take it for a drive to test it as i dont have insurance on it but i feel happy that its not overheating again.

 

 

What could this be? It has only done this once cant find any leaks the water was clean before i changed it but there is a lot of condensation from the exhaust (not sure if its the weather)

 

Would you say its the head gasket or that there was an air lock? Or anything else?

 

Cheers

Dan

[Anthony 1,003]

Unfortunately, it's difficult to know for sure until you test it under load again.

 

If it was in the very cold weather, it could be that there wasn't sufficient anti-freeze and the cooling system was partly frozen, hence it overheated. Coolant loss in that situation could simply be it losing coolant through the expansion tank overflow pipe, especially if the cap is weak and no longer holding sufficent pressure.

 

Only other thing that you can quickly test at home is to see if the cooling system is pressuring excessively - coolant hoses going hard and lots of pressure release when the expansion cap is removed (and the engine not hot enough for suffient pressure to normally be there) are a good indication that there might be headgasket issues.

 

If it all seems OK on the driveway then when you've reinsured it just take it for a quick drive around the local area and see if it overheats or loses further coolant. A drinks bottle of similar on the end of the overflow pipe would confirm or rule out that the coolant was being lost from there.

[shalmaneser 26]

TBH it's always going to be hard to diagnose when it only happened once.

 

Same thing happened to me, just turned out that my water pump seal had given up the ghost and was leaking water, causing the heat to go up and the light to come on. because it only happened when hot and it was raining at the time it was hards to diagnose.

 

TBH as Anthony says you just need to drive it about really to see what it does under load. If you reckon it is the HG then a CO2 test will only be a few quid from a garage, then you know for sure one way or another.

[steve@cornwall 100]

Check the routing of the small bore return pipe from the expansion tank to the top of the rad - I trapped mine between the battery and the intake bracketing, making it overheat. Especially if the battery is not securely clamped.