Bought an overheating '89 750i request troubleshooting help.

[Murtovaara]

I was offered an overheating 750 and couldn't pass it because of the V12!
So i have no clue if this was something really stupid to do...
The car has been in a shop where they replaced the thermostat that was
stuck closed. There is pressure building in cooling system and car run hot.
Car is running, but I will flatbed it home, just to be safe.

I found this notice where Johan bought an 750 with head gasket problems
and when he took it apart the head gaskets was OK? He ended up changing
the whole engine.

http://bmwe32.masscom.net

Want to avoid this and as M70 is quite complex machinery I'm seeking for
advice where to start troubleshooting.
Will start with compression check, but can for example the water pump fail
so that coolant circulation is poor? Will also verify that the thermostat is OK.
I've understood that the M70 cooling system is self-bleeding?

TIA,
Vane

[shogun]

M70 system is self bleeding. The M70 water pump usually lasts a very long time, there were problems with other engines where the water pump failed, but not with the M70 water pump.
Change the thermostat. Dry and wet compression tests and cylinder leak down tests might reveal the location of the leak. A block tester can help determine whether combustion gases are present in the cooling system, a sure sign of a head gasket failure.
How To Tell if a Head Gasket Is Blown:
Coolant leaking externally from below the exhaust manifold
White smoke from the exhaust pipe
Bubbles in the radiator or coolant overflow tank
Overheating engine
White milky oil
Fouled spark plugs

[Murtovaara]

Started working om my 750.
- Changed oil & filter > no trace of water (coolant) in oil.
- Changed plugs, 10 and 11 boot was not well in plug. These 2 plugs was heavily fouled.
Plugs was not very difficult to reach, I pulled the brake fluid reservoir to gain access.
- Checked compression, some variation, but my comp check tool is not much to brag about.
I removed the end covers from intake manifold and lots of black "sand", probably carbon inside.
It just look like black sand and also some oil.
- Checked ignition cables, not in very good condition. #4 no connection to distributor cap terminal.

New plugs NGKBKR6EK, fired up the engine. Run quite nicely, probably with all cylinders.
But there is a thin hose coming from water pump and connect with a Y-joint to radiator end.
This hose then go to expansion tank. When I blow in the hose to exp tank with cap of, the hose is
blocked. Shouldn't it be open?
I bypass the hose after Y-joint to exp tank but still no flow from hose. Isn't this the bleed hose?

Any suggestion how I can verify if there is coolant circulation? Have not driven the car.
I have more or less come to conclusion that the head gasket is not faulty and the variation
in compression is because of carbon and what every debris there is inside. When I get the
cooling issue solved try to run the car and then re-do compression test.

TIA,
Vane

Black sand.jpg1-6.jpg7-12.jpg10-12.jpg

[shogun]

yes, that is for self bleeding the system and often blocked. This is from the M30 which has a bleeder screw on top of the t-stat housing, that the M70 does not have but instead the hose, rest is same, you see that a small stream must come out at the expansion tank http://www.nmia.com/~dgnrg/page_19.htm
Often the small hole at the expansion tank is clogged.
The original pipe from left side water cooler to expansion tank was a thin plastic pipe with a lot of angled portions, most replaced this plastic pipe with a bigger dia. fuel hose and less angles. Later it was changed to a hose 8x13mm, see # 5 http://bmwfans.info/parts-catalog/E3...xpansion_tank/ #11 is just a small hose which is only connected on one side, that is for draining when the radiator cap releases pressure.
There was also a recall for the radiator cap and BMW replaced that free of charge, better install a new one.
https://www.bimmerforums.com/forum/s...cs-recall-1998

[Murtovaara]

Thanks! I got the bleeding system working, a small stream of coolant come out from hole in exp tank
when more than idle RPM. But the the cooling is not working, engine over heat.
I will trash the now installed electric fan and install back an 11 blade fan with clutch.
Also new thermostat as I think it's not working.

- - - Updated - - -

Is it possible that the water pump is not "pumping"? My understanding is that it's a relatively
simple unit and usually the shaft seal fail in them.

[shogun]

On other engine models like M30 and M50 I read about some problems with water pumps, for example for some models they made a kind of plastic impeller which got lose on the shaft and was not turning, M30 some impellers cracked. But have not heard of problems for the M70. Anyway, better you check if the pump really conveys the fluid or not.
Is the belt tight for the water pump and not slipping. Main cooling comes from the visco fan clutch, that must work properly. How to test http://www.mwrench.com/Whitepapers/FanClutchtest.pdf
is the radiator clogged? Do you have a non contact thermometer? With that it is easy to check the temperature differences top left of the radiator = inlet and bottom right = outlet. https://www.enginebasics.com/Engine%...ing%20Pg2.html

[Murtovaara]

Thanks, the 11-blade fan & visko has been replaced with an electric fan. The radiator is quite new and antifreeze has been used.
Ordered 11-blade fan, visco, thermostat and waterpump. As I will change the valve stem seals, will check / change the water pump then.

[Timm]

This should help explain what is going on:

[Murtovaara]

Timm, thanks for the videos. I will re-install new viscous clutch and 11-blade fan.
Please tell me where the electric fan thermostat is located on the V12 engine?
I need to verify that the thermostat and fan are working.

[Murtovaara]

Some search on the web and it's the thermostat switch right side of radiator.
I really appreciate you guys who have taken time to write these DIY articles.

[Timm]

The electric fan is called the auxiliary fan - because it is auxiliary to the cooling system and is primarily used for the air conditioning system. If the compressor runs then so to should the aux fan.

Temperature only affects its operation when the cooling system asks for help (via the radiator outlet temperature sensor indicating insufficient cooling) - otherwise it only responds to A/C demands. If your A/C system has no gas or is not working then the aux fan will do nothing until the cooling system gets into trouble.

[shogun]

you can test the aux fan like this http://www.nmia.com/~dgnrg/page_20.htm
I could fix on some E32 the aux fan by spraying contact cleaner on the spades on the 2 relays, and one time I could fix it by spraying the contact pins of the wire loom which goes into the aux fan directly behind the front grill

[Murtovaara]

Went a bit deeper in the engine, removed intake manifolds and valve covers.
Found 2 banjo bolts a bit loose, but no wear on cam but 2 loose head bolts!
- 1 bolt broken on driver side lower row, fished out the broken piece.
- 1 bolt was loose? on pass side upper row, bolt is looking OK.

Should I just go for it and pull the heads?
Can the heads be removed and re-installed with engine in the car?
What is the tight spot if done engine in car?
My garage is short, had to move and cut the working table to fit the
car in.

Rear water crossover seem to be the tight spot, let's see if I can remove it.

[shogun]

some info here, Removed head without removing M70
http://www.bimmerboard.com/forums/posts/548672
http://www.bimmerboard.com/forums/posts/1254586
https://www.bimmerforums.com/forum/s...asket-write-up
I have not yet done it with engine installed in engine bay, but it is said heads are removed from BMW V12 engine bays all the time without pulling the entire engine/trans. But if you have the chance to pull the engine out, it is much easier, maybe you make a small crane/lift over the engine bay.
training video bmw M70 in German, assembling from minute 8 of 23 minutes https://www.youtube.com/watch?v=aiEfxhB-_Dg

[Murtovaara]

Thanks Shogun for the links, good info.

The rear water channel was not bad to remove, but the exhaust pipes was.
Probably have to remove crossmember under engine to get them back.

Somebody been here before me, the guy before me had the car for eight
years and he has not opened the engine.

One camshaft distributor seal sleeve is cracked and can't find it as a spare.
Would someone have a damaged camshaft to sell so I could replace the sleeve?

IMG_2513.jpg

[shogun]

try to make a repair with a speedi-sleeve, I once recommended it to someone in 2009 which had leaks there and it works, here pictures https://www.7-forum.com/forum/showth...ghlight=sleeve
speedi-sleeve diameter made by SKF 27,94mm will be pushed on the 28,00mm shaft. Should be available in Finland.
https://www.youtube.com/watch?v=09LiVbqL6ss

[Murtovaara]

Thanks, I'll try that if I can't find a camshaft from where I can take this sleeve.

What is your opinion on AJUSA gaskets? I need the head gaskets & top end
gasket kit and these are about 1/2 price than the "brand names".
- Head gasket AJUSA 31,80€ and Victor Reinz 53,45€.
- Top end gasket kit AJUSA 103,38€, Elring 298,80€

[shogun]

Reinz and Elring are probably the better choice, cost more, but considering the work involved....