Overheating

[jenny]

Does anyone have any suggestions as to why I ended up with a huge airlock in my radiator at the weekend

The engine was overheating and I couldn't figure out why - realised the fan wasn't cutting in at 80 and thought the sensor for the fan needed replacing. Did that, still running at 110 degrees

Thought maybe it was the water pump so replaced that (hmmm, now realised that the bar I welded in to strenghten the chassis means that it takes 2 hours to get the pump off)

New shiny water pump in place, the bloody thing is still overheating. Took the cap off the header tank and had a look at the water level while the engine was running. Good job that I can move quickly as just as I got a bit closer to have a good look, it blew about 2 litres of boiling water and a hell of a lot of air out of the system

Filled her up again with the engine running and it's ok now, don't know what could have caused it though. Any suggestions ??

[wilf]

Jenny- it is not uncommon for folks to have trouble getting all the air out of the cooling system on these cars/engines if they have been emptied/refilled - sometimes called an "air lock". The process of getting the air out is often known as "burping".

As to the high temps you are seeing, firstly I would check the accuracy of your guage - I assume it is of the electrical type (i.e. a wire runs between the sensor and the guage, rather than a very small diameter copper pipe)?

Arrange to get the sensor into some boiling water whilst still connected into the car's systems - you will need to rig up an earth wire from the body of the sensor to the car's frame as well. See what reading you get on the guage - this tells you a lot.

As to causes of high temps - air lock, faulty thermostat, blocked radiator, collapsed radiator hose(s), faulty electrical cooling fan or temperature switch. There are some to be going on with.

My suspicions lie in the fact that you did have the fans cutting in at too high a temp - probably boiled the water a bit, introduced air into the system, caused air lock, gave rise to continuing high temps. Try bleeding air out of the system from the highest point you can access.

Also, now you know not to take the cap off the system if the engine is hot!

HTH

[jenny]

Yeah, that makes sense actually, I think the faulty sensor allowed the water to boil causing the airlock. Didn't think of that

Just want to point out that the engine was cool when I undid the cap - I ran it with the cap off the header tank and had a look just when it decided to 'burp' out the airlock I may be blonde but I'm not that daft (although some people might disagree with that)

Hopefully she's ok now, running at 80 degrees. Will just have to keep a close eye on the water (not too close)

Thanks

[neil still building it]

hi jenny
do make sure the water is 'boiling' too not just from a kettle ...they don't get as hot as most people assume.....use a cooking therm. if possible (ok with hamfisted mechanic types) so out with the saucepans...
good luck
NEIL