M20 overheating while driving
 

Driving my new to me vert yesterday I noticed the temp gauge creeping towards the red. This was happening despite driving at 80+kph and it was only 16 celcius outside.

Any ideas on what the source of the problem could be? Faulty thermostat? Clogged radiator?

Thanks a lot,

-Andrew

more then likely thermostat... usually they fail open, but it's possible it failed and is stuck closed... could also be HG, or waterpump, or rad though.

Do some basic checks.

I would check the most obvious. faulty closed stat will cause it to creep. but I would check my clutch fan first. these are not uncommon to go.

Rule of thumb. go with the cheapest. remove the stat - test it in boiling water to see if it opens. if good. re-install bleed the system thoroughly or you will get the same result.
if the problem persists -next clutch fan.

I'd find out from previous owner to see what's been replaced recently.

How is the coolant mix? When did you last change it?

Feel the hoses and the rad that lets you know where the heat is circulating. Hot engine and only warm upper rad/hose means the thermostat is not opening fully. If this is on the highway I think it's most likely the thermostat. If you change it take note of the orientation, or you'll have to pull it apart again to fix it.

Fan clutch is possible but as long as you're moving you don't really need it. On my old car I removed it, and I'd just flick on the electric fan when I was sitting in traffic too long.

Sometimes the coolant sensor goes wonky, not as common but it happens.

thanks for the help guys. I actually just bought the car so I have no idea on the history or maintenance done to it. I will be doing a timing belt, so Ill be replacing a lot of the maintenance items in the cooling system while I'm at it and hopefully that solves the issue.

Issue has been fixed. Turns out the thermostat was all bent up and stuck closed

So you have a vert for a winter beater now lol?

Lol nah I picked it up for a steal because it needed a lot of minor maintenance and a top. I don't really have a plan for it, maybe sell it in the spring, maybe keep it around as a fun cruiser.

Unfortunately, circumstances are forcing me to drive my 325is this winter but hopefully next winter I will have a proper honda winter beater so I can keep the cancer off my e30.

Sweet, do the tb and wp asap if you just bought it

yup those were the first things to be done. Next is a brake job, springs and shocks, then I'll move on to the nightmare of replacing the top :D

Funny thing is the guy I bought it off had owned the car for 7 years and put about 70,000km on it and when I asked him when the last timing belt service was he didnt even know what a timing belt was.

(Shudders)