M50 Head Gasket

[ss2115]

About 99% sure my E34 M50 has a blown head gasket.
Starts up in the mornings or after sitting for a long time with a bit of a stumble which clears quickly enough, and also using water. Low coolant warning comes on about once a week now and sure enough the water is almost out of the expansion tank. No leaks anywhere to be seen. No water in the oil though or visa versa which is good.

So - I am an old mechanic with experience up till about 1988 or so in the trade, but then changed jobs. Kept my hand in doing all my own work on my own cars etc, but not a head gasket on an E34.
Is the M50 easy to do, or tricky, or a pain?
Any pointers or beware advice?
Anything else to be done at the same time? The cars up to 190,000klms.

I have a Bently manual but haven't been overly impressed with it so far as regards in accuracy or its instructions.

[whiskychaser]

I'd suggest taking out the plugs and checking to see if any are 'steam cleaned' first. Follow up with compression and sniffer tests. It would be a shame to put in a new HG only to find the cause of the poor start is perahps that you are losing fuel pressure and the coolant is leaking from the heater valves or heater rad.
If you go ahead use a dealer HG or one from a decent engineering shop. And of course new bolts. Lots of write-ups about replacement around. Just remember the head is quite heavy and unless you remove the bonnet you will have to swing it out on the right side, possibly single handed.

[ss2115]

I'd suggest taking out the plugs and checking to see if any are 'steam cleaned' first. Follow up with compression and sniffer tests. It would be a shame to put in a new HG only to find the cause of the poor start is perahps that you are losing fuel pressure and the coolant is leaking from the heater valves or heater rad.
If you go ahead use a dealer HG or one from a decent engineering shop. And of course new bolts. Lots of write-ups about replacement around. Just remember the head is quite heavy and unless you remove the bonnet you will have to swing it out on the right side, possibly single handed.

Thanks Whiskychaser - sound advice.
I changed the plugs a few months ago suspecting that they hadn't been done for a while. All plugs looked the same so no conclusions there. The water usuage till just very recently has been emptying the expansion tank over a about a three week period. Its only just starting to get a bit quicker. I wouldn't expect the plugs to rust or "clean" with the small amount of water being used.

About two months ago I also thoroughly flushed out the cooling system and added back in 2 litres of fluro green coolant with water top up so I could spot any leaks. The water usage was occuring well before that - in fact since about Xmas but very small. I did find a tiny leak on the bottom radiator hose to radiator connection which i fixed, but nothing else. If there was leaking in the heater box, wouldn't I smell it when the heaters on and eventually see the bright green in the cabin or out on the ground? There's no green stains anywhere under or in the car or under the bonnet.

On the cold mornings of late, the steam out the back seems excessive and is accompanied by a funny smell from the exhaust for a short time which I'm assuming is the fluro green being burnt out of the cylinder it leaked into overnight.

Earlier this week, on a cold start I had compression lock. It took a couple of goes before the engine spun freely and started. Hasn't happened again since, but I think all the signs are there of a coolant leak into at least one cylinder.

I don't think there's any point in a compression check as the leak is too small to see any significant drop in compression. I'm assuming the cooling system pressure is pushing a small amount of coolant into a cylinder overnight as the engine cools down and it sits in the cylinder until start up next day.

If anyone knows of anything else to check I'd appreciate knowing.

[ss2115]

Have had an estimate from a BMW specialist shop near me for Au$1800 - 2000 to replace the head gasket.
Time is against me at the moment, so I might not be able to do it myself.
Does this seem reasonable, given that the head bolts all need replaceing plus all the other parts, cleaning the head up etc etc?

[whiskychaser]

Thats about £1200-£1330. DIY costs are about £200 including pressure test and skim. IMHO thats a lot to pay for labour

[Scott C]

I have done this job. It was due to an oil leak (gasket was corroded) above the exhaust. Other than there is a lot of detail work in getting to to the point of removing the head gasket, it is not that bad. I used another person to help remove the head - it is a beast. You will need to be real careful about front timing chain guide (may not be correct name) as it is plastic and the head MUST be lifted over it or you will need a new one (mine was 95, yours might be diff) both in removal and install.

New head bolts has already been mentioned. They are torque to yield (again if like my 95).

Putting the head back on was no real issue other than lining up the cams and of course being careful not break the front timing chain guide. I bought the cam alignment tool but it is absolutely NOT needed - the head unit (actually cams) is designed so that you can lay a straight edge across 90 deg flats in the cams to align - please check this PRIOR to head or chain removal to save yourself time.


In all honesty, it took me about 5 full 8 hour days but I was very cautious and labeled everything and took pictures (I used to be able to rebuild a chevy v8 in 8hrs). I also thought that the $1500 the dealer would have charged would have been a deal (I didn't think so prior to doing this). I was worried the dealer would push me toward a new head so did it myself to really ensure what the issue was (just a gasket). I swore never to do this job again by the way.

[whiskychaser]

In all honesty, it took me about 5 full 8 hour days

Not surprised you wouldnt want to do it again:-)
OP if you are taking the cams out-which you will have to do if you are having the head pressure tested and skimmed -check out this Pelican article:
Pelican Technical Article: BMW 3-Series E36 Camshaft Removal and Installation
I'd check the valve guides for wear and would certainly install new valve stem oil seals. The old ones will be like concrete.
When you go to put the head back on, make sure the two lugs are in the block. They not only centre the head but hold the gasket in position. I put a couple of thin wooden batons on top of that then lower the head onto them. That way you dont risk bending a valve that is sticking down. When it is all lined up you can easily slide them out. HTH

[Bruno]

I did the job, I think i did it in two steps day one pull the head, send the head to be rebuilt then one day to put it back in.
Takes roughly 5 hours to take off and 5 to put back, pretty straight forward.

I would do it again any day, better than doing a 5 speed swap...

Didn't need any tools as my engine builder set the head so I just had to drop it in the car, I just wish I had put an MLS gasket for the turbo to come.