Coolant header tank venting on vx 1600 8 valve

[MartinL2]

Please can anyone advise why when the engine has been running for about 10 minutes it blows coolant out if the expansion tank cap. When I then stop the engine it seems to blow out a bit more coolant. Cheers Martin 

[Nigel Riches]

Hi Martin, there are various reasons for this situation, some easy and quick to fix, others not so.

Start at the easy quick end, have you had a look at the cap on the expansion tank? Is the system set up as a "recovery" system, sounds like it probably has been. So the coolant expelled as the engine heats up, is drawn back as it cools down, hence, expansion system. Now, if the seal in the cap is NFG the required system pressure will force fluid past the seal, so could be as simple as a new cap.

You mention it expels more fluid after stopping, probably because the coolant continues too heat up as it draws heat from the engine, thus continuing to expand. So, have a look at the expansion tank cap, or for a few coins, get a new one.

This is really at the cheap end of the problem range. And as I have no knowledge of the VX engine have no more detailed info, but, this sort of problem often indicates a failed cylinder head gasket, so hang on for further adventurers in 7 ownership.

Nigel.

[paul_w]

Hi Martin - from your previous thread on this issue it seems you replaced the cap, so it's unlikely to have failed again. If this and careful bleeding hasn't helped then it does point to potential head gasket issues, but there is a quirk to this particular engine that's you should be aware of. Caterham originally left the thermostat out on these engines, as they were having problems with air locks and overheating (hard to believe since it is a bit of a bodge, but true). It is possible to fit a thermostat, but you have to modify the coolant hose routing to prevent the issues - I did this on mine following previous threads on here and it worked a treat - I wanted my heater to work on cold days, not unreasonably!

So before looking at head gasket problems, I would check to see if someone has fitted a thermostat and try removing it as Caterham did and see if that helps. If so and you want to go back to a stat I can try to dig out the tweaks to add one.

Worth a try at least, since it won't cost you anything!

[Nigel Riches]

Back again Martin.

My apologies, I wasn't aware of your previous post on this matter.

Bailing out now, hope you get it sorted.

Nigel.