running temperature

[angoose]

Hey all,

Need to pick your brains again.

A little back story. The car was running fine and then the temp gauge started creeping up to 3/4 and stayed there. Then climbed higher so I pulled into the services. I let it cool and topped up with new coolant then set off, not far down the road I had the same problem. Got picked up by recovery guy he suspected head gasket.

Upon getting delivered back to me I started to try and work out if it could be anything else. No leaking hoses etc. So i swapped out the thermostat and so far so good. Been out on a few short drives and go a bit further each time just to see how we get on.

All seems good done a bit of town and country roads and been out for an hour or so but the car doesnt seem to get up to half way on the temp gauge. Running between 1/4 and half. Is this a problem? I havent done a motorway run yet but a little apprehensive to do that just yet.

Many thanks,

Angus

[Cloggy Saint]

Between 1/4 and 1/2 is the correct position for the temp' gauge

[angoose]

Cloggy Saint,

Thanks for getting back to me so quick on this. Glad to hear that. I figured it should be ok but after it over heating been watching the gauge like a hawk.

Thanks again

[BenHar]

Between 1/4 and 1/2 is the correct position for the temp' gauge

True for a 6 cylinder engine which should have an 82 degree 'stat.

If it's a 4 cylinder it should have an 88 degree stat and run at the halfway mark.

Ben

[jmc330i]

As above, all my 6 pots have run at just over 1/4, my 4 pots have all run at bang on 1/2.

[angoose]

Its a 6 cylinder. Thank you all for your help. I really appreciate it.

[Brianmoooore]

The fact that you've asked about the correct gauge position suggests that it wasn't correct before. What's the temp. stamped on the old 'stat? Does it have BMW stamped on it?
The temp. scale of the gauge isn't linear - it's compressed at the low end and at the high end, so as long as the needle didn't go into the red, the car didn't overheat by as much as you might think.
You haven't mentioned the low coolant light in the overhead panel. If the coolant didn't get low enough to switch this on, there was sufficient coolant still in the engine all the time, so this wasn't the cause of the overheating.
M20s (with sufficient coolant in them) overheat for three reasons when they're moving - thermostat troubles, water pump rotor disintegrating or slipping, and an airlock at the back of the head in the heater circuit. The airlock, once the car has been properly bled after work on the cooling system, can only be caused by a slight leak of combustion gasses into the cooling system, either by a failed head gasket or a crack.

[angoose]

hi brianmoooore,

Thank you for taking the time to reply to question. I dont recall the coolant light coming on.

As for the temp gauge it went near red but I had pulled over then and as was getting steam from the coolant reservoir.

I asked about what position on the temp gauge as the car is still fairly new to me. When i first had the car the temp gauge ran around halfway. Then on that journey it after a while crept to 3/4.

When we changed the thermostat there was some debris in the thermostat housing. Something that looked like a but of a seal and the other vaguely resembled wax.

The thermostat appeared to have been replaced before and the seal almost appeared glued in and wasnt easy to removed but we removed it carefully and replaced the seal and new thermostat.

I queried the temp gauge position as its now running at 1/4 which it never has since i've owned it. Which is why I wanted to check this was normal.

So far ive done a good few trips and she seems to be running well.

[Brianmoooore]

If all is OK, then perhaps it was just a failed thermostat, and possibly the wrong 'stat had been fitted - wouldn't be the first time I've seen it.
BTW, if the airlock at the back of the head occurs, as well as overheating, there will be no heat from the heater, even with the knob turned fully to 'red'.

[angoose]

Ok i'll check the heater when I next take the car out and let you know wht happens. thanks again

[angoose]

Hi just to let you know that the heaters working well so no airlock at the back of the head

[BristolE30]

Between 1/4 and 1/2 is the correct position for the temp' gauge

True for a 6 cylinder engine which should have an 82 degree 'stat.

If it's a 4 cylinder it should have an 88 degree stat and run at the halfway mark.

Ben

My 316 carb has an 80c thermostat. 88 is a lot higher, was it different on certain models?

Cheers
Jo

[Brianmoooore]

My 316 carb has an 80c thermostat. 88 is a lot higher, was it different on certain models?

Cheers
Jo

Criteria for deciding the thermostat opening temperature:

The hotter a petrol engine runs, the more efficient it is.
The limit is reached when local boiling occurs at some point in the cylinder head.
The higher pressure the system runs at, then the higher the temperature will be that the local boiling occurs at.


The newer an engine design is, local hot spots in the cylinder head are likely to be reduced by better design.
With newer, more advanced materials, the system pressure can be increased.

Your M10 is the oldest E30 engine, then came the M20, which runs hotter, initially at the same pressure, but increased in later versions. After that was the M40, which runs hotter again, and at the higher pressure that the later M20s run at. Finally comes the M42, which runs at the same temp. as the M40, but at a considerably higher pressure.

Your M10 engine was originally designed with a crude thermostat that simply blocked flow to the radiator while the engine was warming up, stopping the flow inside the head and causing hot spots. This was improved by adding the weird self contained 'stat assembly used on the E30 M10, which just hangs in a nest of pipes, rather than a 'stat built into the engine as on all others. The extra pipes allow the coolant flow in the engine and heater to be maintained from cold. I suspect the M20 was originally designed with a flow stopping 'stat as well, because of the excess of large coolant pipes, but this was sorted by a clever redesign of the thermostat housing, plus the extra pipes.

[BristolE30]

My 316 carb has an 80c thermostat. 88 is a lot higher, was it different on certain models?

Cheers
Jo

Criteria for deciding the thermostat opening temperature:

The hotter a petrol engine runs, the more efficient it is.
The limit is reached when local boiling occurs at some point in the cylinder head.
The higher pressure the system runs at, then the higher the temperature will be that the local boiling occurs at.


The newer an engine design is, local hot spots in the cylinder head are likely to be reduced by better design.
With newer, more advanced materials, the system pressure can be increased.

Your M10 is the oldest E30 engine, then came the M20, which runs hotter, initially at the same pressure, but increased in later versions. After that was the M40, which runs hotter again, and at the higher pressure that the later M20s run at. Finally comes the M42, which runs at the same temp. as the M40, but at a considerably higher pressure.

Your M10 engine was originally designed with a crude thermostat that simply blocked flow to the radiator while the engine was warming up, stopping the flow inside the head and causing hot spots. This was improved by adding the weird self contained 'stat assembly used on the E30 M10, which just hangs in a nest of pipes, rather than a 'stat built into the engine as on all others. The extra pipes allow the coolant flow in the engine and heater to be maintained from cold. I suspect the M20 was originally designed with a flow stopping 'stat as well, because of the excess of large coolant pipes, but this was sorted by a clever redesign of the thermostat housing, plus the extra pipes.

Interesting. Thanks for that Brian.

My engine temp has been creeping up just above the half way mark, pretty much since I bought it. It definitely increases at stops, then cools down a bit once going, especially going down hill. Replaced the thermostat and it seems to be working (lower rad pipe hot). Another interesting thing I noticed yesterday was that the heater matrix made a strange gurgling noise the other day and the engine temp instantly went up a bit - do you have any ideas what this could be? I did notice some coolant marks on the side of the glove box (photo), but I figured it was from an earlier accident.. Thinking of replacing fan clutch but it does seem to be working. May also try some Holts Speed flush as I guess radiator could be a bit clogged. Photo attached of where it fluctuates too...

Appreciate any help
Jo

[BenHar]

If it increases when stopped the fan clutch is on it's way out.

Ben

[Brianmoooore]

If it increases when stopped the fan clutch is on it's way out.

Ben

Viscous fan coupling isn't triggered to lock until hot enough air is reaching it from the centre of the radiator. By this time the coolant temp. of the engine will have crept up a couple of degrees. If the needle climbs as far as the 3/4 white mark or continues gradually creeping upwards then the fan coupling is suspect.
It's a crude system, but because of the low component count, tends to be a reliable system.

[BristolE30]

If it increases when stopped the fan clutch is on it's way out.

Ben

Viscous fan coupling isn't triggered to lock until hot enough air is reaching it from the centre of the radiator. By this time the coolant temp. of the engine will have crept up a couple of degrees. If the needle climbs as far as the 3/4 white mark or continues gradually creeping upwards then the fan coupling is suspect.
It's a crude system, but because of the low component count, tends to be a reliable system.

Is it normal for my temp gauge to be creeping up like this? It’s disconcerting to say the least as it feels like if I really ran it hard it could go higher. I’ve heard some people say it should never go higher than half.

What were your thoughts on the gurgling noise? And the Holts Speed Flush? I’ve heard people getting good results from it...

Cheers!

[BristolE30]

If it increases when stopped the fan clutch is on it's way out.

Ben

Thanks, yes I think may just replace it as it’s probably never been. Could help!

[BristolE30]

Update:

Replaced the fan clutch and all seems to be well! Temp gauge is staying constant in the middle!

[Foe]

Fair play, and fingers crossed all stays well

[Brianmoooore]

You still haven't convinced me there was anything wrong with the one you removed. New viscous couplings tend to be very stiff in their unlocked state, and will apply more drive to the fan than they should, until they loosen up after a few hundred miles.
This extra air flow will prevent the coolant getting hot enough to trigger the coupling most of the time, which will be reflected by the gauge.
No harm will occur, other than a slight reduction in power/ increase in fuel consumption for a while.

[BristolE30]

You still haven't convinced me there was anything wrong with the one you removed. New viscous couplings tend to be very stiff in their unlocked state, and will apply more drive to the fan than they should, until they loosen up after a few hundred miles.
This extra air flow will prevent the coolant getting hot enough to trigger the coupling most of the time, which will be reflected by the gauge.
No harm will occur, other than a slight reduction in power/ increase in fuel consumption for a while.

Ah so you are saying the problem could just come back? After removing the old fan clutch it does seems to be pretty knackered, it’s spins incredibly freely and make a bit of a grinding noise. There is almost no resistance.

I didn’t try the newspaper trick whilst it was really hot, but I could stop it by hand at around 1/4 engine temp.

[Brianmoooore]

I'm not saying the 'problem' will come back - I'm saying it's quite likely you didn't have a problem in the first place! The engine will come to no harm if the gauge needle remains within the two outer white marks.
However, if there's a grinding noise when you spin it, the centre bearing is probably shot, so it's probably for the best that you've changed it.

[Oseanosea]

Just wondering, what is the “Newspaper Trick” mentioned above?

[Cloggy Saint]

Poke a rolled up newspaper in the fan when it's turning. If the paper gets shredded then the fan's good, if the paper stops the fan then it's buggered.

[Brianmoooore]

99% of the time the engine is running, the fan shouldn't be "locked up", and the newspaper shouldn't be shredded. In fact, it's possible to stop the fan with your fingers - not that I'm volunteering.
The fan should only lock up when the car is moving slowly for some time or has been stopped a while with the engine running. Under these circumstances, the fan coupling should eventually lock, and it's easy to tell when this has happened by the sound the fan makes. If you press the throttle it sounds like a propeller aircraft on its take off run.
The two things that go wrong with these couplings are that it fails to lock up, and the engine temperature continues to climb past the third white line under the circumstances above, or the centre bearing seizes up, and the engine sounds like an aircraft all the time.
The latter happened to me a couple of years ago on the return journey from Monaco along the 'Route Napoleon' to Grenoble. Thought it was some kind of transmission failure at first, until I worked out what it was.

[Sleepless]

Guys I need your help again!

A few months ago, I noticed that the heater on my E30 (318i M40B18 engine) was not producing hot air constantly. So, I decided to clean the cooling system on a specialized workshop. Given the opportunity, the thermostat, the water pump and the fan clutch were replaced with new ones (a 88 C thermostat was chosen) and the coolant fluid was replaced with BMW (50% mix with distilled water).

So far so good, and the heater is working normally now, but I'm having a strange behavior on the temp gauge. At low speeds, and regardless the outside temp, it sits below the center line and at high speeds it sits just above the center line (see photo). Needless to say that before the aforementioned changes the needle was stuck in the center line no matter what.

Is this behavior normal or do I need to take some action?

Any feedback will be much appreciated. Thanks in advance

[Sleepless]

Anyone?!

[Brianmoooore]

Don't forget that there's only a few degrees between the quarter white line and the three quarter white line, but the needle shouldn't move around like that, except when the engine is idling/traffic, when it gets up to just about where shown in the pic., before the viscous coupling locks up.
The thermostat keeps the engine temp. up to a certain point, so if it drops below that, it's the 'stat that's faulty. If it never drops below that point, but sometimes rises above it, then it's the radiator or water pump at fault. New doesn't necessarily mean good.
Make sure the system is bled properly before you do anything. Air in the system can make the gauge wobble a bit.

[Sleepless]

Thanks a lot Brian. So, I'll start with the thermostat and I'll see how it goes. Next step is the radiator...

[Sleepless]

Thanks a lot Brian. So, I'll start with the thermostat and I'll see how it goes. Next step is the radiator...

Finally, the crappy chinese-made Magneti Marelli thermostat was replaced with an OEM Wahler and the temperature needle is dead center again.

Thanks a lot @Brianmoooore