M42 running really hot after replacing thermostat

[MrT8064]

Bought the car with no thermostat in it, and was given a brand new one ready to go in. I installed it ok, and think I bled the system properly. The car now runs really hot... Any ideas? May have to take the thermostat out again if I can't think of anything!

[jmc330i]

Why did the previous owner run it without the thermostat?

[maxfield]

Why did the previous owner run it without the thermostat?

Obviously to cover up a fault with the cooling system.

[MrT8064]

Hmm well that doesn't sound like good news...

what other parts to the cooling system are likely causes? i'm pretty sure the water pump is going well.

Also, I used instant gasket maker rather than a correct BMW one, is there any chance that some gasket maker getting in the little channel between the compartments in the thermostat cover could cause me issues?

Thanks!

[jmc330i]

Why did the previous owner run it without the thermostat?

Obviously to cover up a fault with the cooling system.

Yup, but I didn't want to point the out obvious, I figured (hoped) the OP might of asked the guy selling before he bought the car.

what other parts to the cooling system are likely causes? i'm pretty sure the water pump is going well.

Also, I used instant gasket

Instant gasket isn't the best, but as the thermostat had been removed, I would say the problem was present before you even got the car

Is it running hot while on the move or while stationary, or both?

[MrT8064]

Running hot more when I'm moving than stationary. Under very gentle load it sits just above the middle, but when going up a hill quickly rises to above the next bar

[jmc330i]

Middle to 3/4 is fine (maybe just over in the recent hot weather), if it rockets past 3/4 and near the red is not so good.

Are you sure you bled it ok? Does the heater blow nice and hot air?

[MrT8064]

Hmm thats interesting. I'm thinking perhaps I didn't bleed it properly, I do get nice hot air however.

Would it be best for me to totally drain it and start again? I spent a good time googling bleeding procedures and didn't really find any consistency between what people where suggesting. From what I understand I should:

Remove coolant tank cap, remove bleed valve screw.

Fill with coolant until it settles on half way.

Get friend to turn on the engine while I add more coolant until it starts to jet out of the bleed valve.

Screw back in bleed valve. Screw back in Tank cap.

Turn engine off.

Check levels

Doesn't quite seem right to me but that seems to be what a few people have done!!

[capri_rob]

Could be just a cheap-ass rubbish thermostat thats not opening properly - try fitting a genuine one before writing the engine off.

[MrT8064]

Could be just a cheap-ass rubbish thermostat thats not opening properly - try fitting a genuine one before writing the engine off.

The one I have is Circoli - I think thats a eurocarparts standard part. Does anyone have experience with these?

[scallyally]

Check operation of stat by suspending in saucepan of hot water to ensure stat opens fully. Also flush out radiator.

[MrT8064]

I'll give that a go tomorrow. Does my bleeding procedure sound correct?
Thanks

[pac1982]

it was doing this when i sold it to the guy before you.

Prehaps he never did fit a new engine and its the same donk?

I was fairly sure the head gasket had gone if it is still running the same engine

[ajay]

When bleeding/filling the cooling system, turn the heater temp up to its hottest setting and the interior fan on full.

[MrT8064]

Hmm interesting. The seller certainly gave me enough spare parts to suggest an engine swap had been done!

What colour was the rocker/valve cover when you had it? It's white on here.

I'm going to bleed the system again soon and will report back

[Grrrmachine]

If the engine has been swapped, which would include ancillaries like the water pump and fan, then I'd hazard that the rad is the original one, and is probably knackered.

[MrT8064]

Hmm or perhaps I should take a look at the water pump. Am I right in thinking that the fan shouldn't really spin at idle? The seller gave me an electric fan and a couple of relays but I don't know what to plug in where!!

[Grrrmachine]

Running hot more when I'm moving than stationary.

That's pretty much the complete opposite of "broken fan" symptoms. If your fan was buggered it would overheat when stationary, as there'd be no flow through the radiator.

Electric fans are only fitted during engine swaps or bodge jobs. Test your existing fan:

http://www.e30zone.net/e30zonewiki/inde ... ooling#Fan

[MrT8064]

Right, I totally drained the coolant again.

Filled with 90% water/10% coolant (just to test the car, will not run for more than a couple of days like this)

I bled the system again and took it for a drive.

This time it still was running hot, but no where near as hot as yesterday. The needle was sitting about 3mm above the centre line (so somewhere between where it should be and the next bar). Most of the time I kept the revs above 3,000 once it had warmed up. It moved up and down slightly based on how I was driving.

Assuming I bled it correctly (this time), could the wrong ratio of water increase the heat or do I still have air in the system/ a faulty component?

-----

I'm going to test the viscous fan now. Seeing as I have this electric fan, is there an install guide for it about? I think the seller said it was from an E36, and included 2 BMW relays.

[Grrrmachine]

Replacing viscous with electric will not solve your issues. But if you must, here you go:

http://www.e30zone.net/e30zonewiki/inde ... ectric_Fan

[jmc330i]

As above, the fan won't be an issue if its keeping it cool while stationary. Replacing a working viscous fan with an electric fan isn't worth the bother.

I'd hazard that the rad is the original one, and is probably knackered.

This would be my guess. Rads are service items (I think 100k) but are usually overlooked as they seem fine from the outside
I would guess this one is partially blocked.

As long as there's no sign of water and oil mixing, I'd be changing the rad.

[n1tr0_9]

Does it actually blow its coolant out, or does it just show up as hot on the cluster?

[MrT8064]

Right, I've been out for another drive having let another couple of bubbles out of the bleeder valve.

Under normal driving the temperature is now reading only fractionally above the mid point.

Under heavier load (hills/harder acceleration) it still creeps up a bit.

I have also realised that the temperature is creeping up at idle (to 3/4). And putting a bit of card in the way of the fan still stops it very easily. So it sounds like the viscous fan might be A problem if not THE problem!
-------
Deffo no sign of oil and water mixing.

Would using the correct coolant ratio reduce my temperature a little further? - Can I just open the tap at the bottom and top off with fresh coolant or do I need to bleed the whole system?

Worth mentioning i'm running without the fan shroud atm, didnt thin that would make much difference?

Thanks so much for the help!

[n1tr0_9]

Fan shroud does make quite a difference, so put that back in if you have it, then take it for a run again.

[MrT8064]

I'll put it on now and go for another run! - This time to the petrol station


___________

Update: Been for a drive with the shroud on. I tried a bit of 70mph cruising, the needle sits just over the centre point still, and rises slightly going up long steep hills. Could this be a viscous fan symptom?

[n1tr0_9]

Also, see in the photo below where ive drawn the arrow, there is a slot. If you fitted the housing with instant gasket you may have filled this in. I cant remember why, but i think its important and helps with bleeding out bubbles. Some clever person will come and correct me shortly.

[MrT8064]

Thanks for that, yeah I did spot the little channel - wasn't really sure what it was for. But I tried to keep instant gasket out. Perhaps I should check again!

Would a bad fan cause slight over heating at normal speeds, and increased over heating under load?

Should the correct coolant ratio make a difference?

Thanks!

[MrT8064]

I've had a go at the old newspaper test and even when the engine is really hot - the blades stop easily.

Seeing as i've been given this electric fan, I may as well use it... if I can figure out the wiring part of the 'how to' guide.

Here's a photo of my radiator. Is that brass nut coming out of the side a blanking plate for a thermostat? Anyone know if those loose wires have anything to do with the fan system... or something else? Looks like they could be plugged into each other.

[pac1982]

Hmm interesting. The seller certainly gave me enough spare parts to suggest an engine swap had been done!

What colour was the rocker/valve cover when you had it? It's white on here.

I'm going to bleed the system again soon and will report back

It was me that painted the engine white, however the rocker cover is an easy change so its not a dead give away that its still the original engine.

if it is the same engine i fitted a new water pump to it just before i sold it, it should be one of the ones with a metal prop not a plastic one

[Grrrmachine]

Please, just give up on this electric fan idea. It's a massively complicated solution to an easy fix, which is to unbolt the viscous and bolt a new one on.

Coolant ratio shouldn't make a noticeable difference to the operating temps of the cooling system.

As for this:

Would a bad fan cause slight over heating at normal speeds, and increased over heating under load?

Depends what your definition of "under load" is. As I said, a bad fan will cause temps to go up when idling, not when moving.

Stop being a cheapskate, buy a new rad and viscous, and then see what happens. These are service parts anyway, so you need to replace them at some point.

[MrT8064]

It was me that painted the engine white, however the rocker cover is an easy change so its not a dead give away that its still the original engine.

Hmm... Well I was given a newly shot-blasted rocker cover to go with the car. So possibly your old one was back on as a temporary solution.

Did you have some timing chain rattle at 3,000?

[MrT8064]

Perhaps I should give up on the electric fan plan, I just like the idea of taking a bit of strain off the engine.

Depends what your definition of "under load" is. As I said, a bad fan will cause temps to go up when idling, not when moving.

By under load, I mean accelerating up a hill!

Temp only just over normal whilst cruising at 70 (rpm about 3000).

Are you sure this isn't a fan issue?

[pac1982]

It was me that painted the engine white, however the rocker cover is an easy change so its not a dead give away that its still the original engine.

Hmm... Well I was given a newly shot-blasted rocker cover to go with the car. So possibly your old one was back on as a temporary solution.

Did you have some timing chain rattle at 3,000?

engine was noisey but i've never heard a timing chain rattle first hand so not sure

bear in mind with the over heating thing because of the front end on an E30 being the way it is, and its almost mustang like front grill its practicly air cooled when driving along at a decent speed

[n1tr0_9]

Id also not bother with an electric fan. Get a known good 2nd hand viscous and try that out first. Your does sound a bit past it if it doesnt lock up when its hot.

[Grrrmachine]

If the car's moving then it should be getting airflow over the radiator, keeping things cool. It's when there's no airflow (i.e. when stationary) that the fan is needed to keep things cool.

BTW, an electric fan still places load on the engine - the power making the fan go round comes from the alternator...