Cooling System 316/M10 +1hour, struggling

[ejhbristol]

Hi,

I've got an E30 where something's wrong with the cooling system and I wondered whether anyone out there could help me. Being an engineer myself (albeit not on cars) hopefully I can give a lot of circumstantial evidence to help get to the root of the problem.

1. I'm not losing coolant.
a) have in the past, driven with air in the system, but I know to jack it up now, squeeze the tubes while running it etc. So I don't think it's air.
b) also had a mechanic get one of those things that you can fit onto the top of the radiator with a bung on it, to check if it could detect any engine gases (it had like an airlock system with another chemical that would change colour if it was gasket related)
c) looked around for leaks, and while in the past I did have some, it's good on that score now - I went on a 3 hour drive and the level was just the same the next day when I checked.

2. The Problem: After about an hour, or slightly less, the temperature gauge starts to rise a bit, and alarmingly, jump!
a) this problem can be partially fixed, by opening the heater system. initially just letting the natural vented air coming in from doing 60 on the motorway, with the temperature set to hot.
b) after driving for a bit longer, say 2 hours, this stops working, and I need to have the fan turned on, 2 or 3.
c) there is no problem with the hot air coming into the car (I know when you have air leaks it can not be that cold), this air is nice and hot.
d) this past time I drove 3 hours, and by about 2 hours 30 I was getting worried that I wasn't going to make it - the needle was starting to go past middle, and starting to lightly jump up to 3/4's. in a moment of inspiration I reached across and opened the bonnet from the passenger side, while driving , so I was driving with the bonnet ajar... this seemed to do something, and I managed to nurse it the rest of the way with it cracked opened, and the heater on 2 or 3 (windows down and everything)

So, as I mention - I don't think it's the gasket (mechanic tested that 1b), or leaks (the mechanic friend of mine had us manually pump up and pressurise the system and there was no pressure loss).

So I'm assuming that either my fan isn't working properly, or the pump isn't. I think I read somewhere that if the pump isn't working, the tubes shouldn't be pressurised much, even after working it hard? Mine definitely get pressurised.

Anyway - if anyone is able to confirm it is the fan, or something else... that would be really helpful! I'll try and post some pictures of my car on the newbies page... I'm actually trying to sell it, but wanted to try and fix this before passing it on. Cheers,

PS
I've been a bit fancy and uploaded a youtube video of the needle doing it's thing. sadly the video only shows it flicking down... but often it flicks 'up' (i.e. towards the hotter temperatures).

Elijah

[Brianmoooore]

The needle jumping as quickly s that can only be an electrical fault. The sensor cannot respond to temperature changes as quickly as that.
There is a well known problem with the E30 instrument cluster that causes the temp. gauge to jump around, and that is when the single brass nut on the back of the cluster case that holds the gauge in place becomes loose, drops off, or otherwise causes a poor connection.
The first thing to do is to check out this nut, and see if that cures all or part of the problem.

[BristolE30]

Yea you can see the way it flickers like that, almost defo the brass nut. M10’s do have a tendency to creep up in temperature tho, a lot of people have had the same experience as you including me. What helped me a lot was getting a new alternator belt as this drives the water pump. Mine was loose and old

[ejhbristol]

Yea you can see the way it flickers like that, almost defo the brass nut. M10’s do have a tendency to creep up in temperature tho, a lot of people have had the same experience as you including me. What helped me a lot was getting a new alternator belt as this drives the water pump. Mine was loose and old

Thanks! that really helps actually. I didn't respond to the other post, because I just knew that it was more than simply electrics - the problem only happens on longer drives. It's not flicking all the time, and when it's still, you know there's another problem going on. My alternator belt IS old (a mechanic friend of mine said he saw cracks), although we did try to tighten it not that long ago... sounds sensible though. The other things I was thinking was: a) waterpump or b) the wax coupling thing for transmitting to the fan

[Brianmoooore]

Examine the inside edge of the belt, not the sides. If the inside edge is clean and polished, the belt is more than worn out, and tightening it will achieve nothing.
Cracks make no difference at all, right up to the point that it breaks.
Definitely sort the electrical fault ASAP, so that you can keep tabs on the engine temperature properly. With the electrical fault the car could overheat without you being aware with the right combination of circumstances.
The 'wax coupling thing' does nothing when the car is moving. It only comes into play after the car has been idling for some time.

[BristolE30]

Yea you can see the way it flickers like that, almost defo the brass nut. M10’s do have a tendency to creep up in temperature tho, a lot of people have had the same experience as you including me. What helped me a lot was getting a new alternator belt as this drives the water pump. Mine was loose and old

Thanks! that really helps actually. I didn't respond to the other post, because I just knew that it was more than simply electrics - the problem only happens on longer drives. It's not flicking all the time, and when it's still, you know there's another problem going on. My alternator belt IS old (a mechanic friend of mine said he saw cracks), although we did try to tighten it not that long ago... sounds sensible though. The other things I was thinking was: a) waterpump or b) the wax coupling thing for transmitting to the fan

Where abouts in Bristol are you? I’m north, in Kingsdown