Overheat!

[Arryhall]

Now I'm scared from all the horror stories.

I was driving around today and noticed the fan coming on a fair bit, but then it has been and was hot. About 200 yards from home, the needle went straight into the red from half way where it had been all day, the IPK said "Enngine temperature" and then everything dropped back to normal.

I coasted home as I was that close, and opened the bonnet. After a while of cooling, I opened the coolant reservoir and it was fine. Then it guggled and burbled and belched and went down a fair bit! I added about a litre and a bit of coolant and it is now full again.

Right: how worried should I be?
I've read repeatedly about HGF from overheating and I have been careful to check fluid levels a lot. There was obviously an air lock, and I've had the air con going full blast, but I don't know if this will make a difference.

Wasn't thrashing the car, hadn't been going that far really, shoved my head under the car after filling up with coolant but didn't see ANY drops of water anywhere. Didn't see any hint of fluid in the engine bay or under the car. In fact, apart from a general misting of oil (coz I haven't ever cleaned the engine!) the whole area was bone dry.

Anyone have any advise? What should I do?????

[SD1too]

Originally Posted by Arryhall

What should I do?

Hi Matthew,

First, don't panic!

Secondly, check the coolant level in the expansion tank frequently and when the engine is cold. Remember not to overfill it; the 'max' marker is right down near the bottom of the tank.

Thirdly, perform the 'demist test' to ensure that your radiator fan is working on the slow speed. When running the air con. it should be, so if it was switching on and off that's probably your problem.

Fourth, tell us if you have had any work carried out on the cooling system recently.

Simon

[Arryhall]

Thanks Simon!

In the last couple of months, after I bought it I noticed the passenger side heat wasn't actually hot, so I ran engine flush through it, drained it and filled up with new antifreeze. It took the handbook recommended quantity (6.something) litres eventually and seemed to be settled as every time I checked it, which was daily, it was the same level. Had to add just a bit a couple of times as it gradually belched out the last air pockets (or so I thought).

Couple of weeks ago, I had the air con serviced, but I have no idea if that would effect anything.

I topped it up after the engine had cooled, and have been out a few times watching the engine temp. and checking the coolant a lot, and it now seems fine. Looked under the car and still can't see any leaks or any signs of a leak.

The engine fan seems to run fine with the air con, and the fan kicked into high speed when the engine said it was overheating so the fan seems fine.

Slightly curious about the overfilling thing though. I found that in order to fill it to the max mark, to reach that mark, I had to slightly over fill it as the marker is, as you said, right at the bottom. Seems a bit of a daft design to me.

Hopefully it was just an anomaly, but the horror stories of overheating due to coolant loss meaning instant head failure is scary when the car suddenly overheats, hence the panic!

[T-Cut]

Originally Posted by Arryhall

Slightly curious about the overfilling thing though. I found that in order to fill it to the max mark, to reach that mark, I had to slightly over fill it as the marker is, as you said, right at the bottom.

Just flood the marker so 'MAX' is covered. Anywhere from there to 10mm deep is fine. This allows around half a litre free space for thermal expansion without submerging the relief valve. The valve needs to vent air and water vapour, but not coolant.

This is about right:



TC

[SD1too]

Originally Posted by Arryhall

... drained it and filled up with new antifreeze.

Ahh, did you follow the MGR approved procedure for refilling and bleeding using the special plug in the radiator bottom hose? If not, you probably have an air lock. I can post the procedure for you later tonight if you need it.

Simon

[Arryhall]

Originally Posted by SD1too

Ahh, did you follow the MGR approved procedure for refilling and bleeding using the special plug in the radiator bottom hose? If not, you probably have an air lock. I can post the procedure for you later tonight if you need it.

Simon

Errrrr.....I didn't know there was a bottom hose, let alone a special plug! I asked a mate of mine who talked me through it a bit, but I admit to probably having made a hash of it. It seems to have been okay for about 800 miles until the other day, so thought I'd got it right, but apparently not!

[SD1too]

Originally Posted by Arryhall

I didn't know there was a bottom hose, let alone a special plug!

It's large diameter and can be found in the battery box area. The bleed screw on the 1.8 is actually hexagon headed in a short length of pipe I believe, with a hose at both ends.

Here's the MGR procedure. It's worth a try.

Simon