1986 325i Baur Best way to Re-torqe head

[Avinit4]

hello people
Have rebuilt engine etc but am losing oil from somewhere at front and rear of engine.
Defo not cam or crank seals at front. The engine is super clean and very easy to see, trouble is it seems to begin at the head gasket next to timing belt. Which makes me think that maybe I f*-*-* up toquing the head down. as wasnt easy and my large torque wrench would jump every now and again.

regards oil from rear, same prob cant identify where from other than begins at bottom of Head.

Hense my question is, I'm thinking I need to re-torque the head and am wondering if I should just check each bolt to see if 1 or 2 not as tight or do I have to remove all headbolts and replace with new set.
I need to do valve gaps again anyway as one's gone loose so may as well check the head bolts while there! One of the 2 links to engine pic should work

http://s494.photobucket.com/user/AVINIT ... a.jpg.html

http://i494.photobucket.com/albums/rr30 ... b9aefa.jpg


Any help appreciated

[Brianmoooore]

The only place you will leak oil from the head to block joint on the M20 engine is from the RH (exhaust) side of the engine, about a quarter of the way back. Any oil leak at the back is likely to be the 'D' shaped rubber plugs that block the cutouts where the rocker shafts are slid in. There are two of these at the front as well, which can also leak.
M20 head bolts are of the 'stretch' type, and are torqued down by first tightening to 30Nm, in the usual sequence, then turning the bolts through another 90 degrees, in sequence, then finally another 90 degrees in sequence.
There's no figure for final torque, and you're not really supposed to slacken them off and re use, although some say that one reuse is OK.
After the initial 30Nm of tightening, I always place a mark on all the bolt heads at '12 o'clock', with a permanent marker, so that I can easily see that all the bolts have been turned a further half turn when the job is finished.

[daimlerman]

[Avinit4]

Thanks Brianmooore I'l just have to keep looking! I know the front issnt down to the half moon shaped rubber seals. I renewed all seals when rebuilding. Ehen wiped clean the front starts from the underside of the head gasket that protudes about 1mm out.
It was wishful thinking to hope it was the headbolts but thats life.
I can check the rear half moon rubber when I reset valve gaps... and never know I may discover more about the front leak then... Thanks for advice

[daimlerman]

Also look at the camshaft oil seal,if it's not correctly seated,this will give a bit of a weep as well.
M20's in general do lose/leak a little oil,I find that a 15/40 is the thinnest that mine will tolerate without spitting the stuff out too much.

[Avinit4]

Brianmooore....... Anychance you can expand on cause of oil leak from the head to block joint on the exhust side of the engine thats about a quarter of the way back?
The D shaped rubber plugs are fine and theres no oil above the head to block joint front or back of engine.
Theres also no oil on the left (inlet manifold) side of the engine.
So i'm thinking oil leak originates at the point you mention then runs both ways along the tiny head gasket lip thats showing to the front and rear of the engine before traveling downwards towards the sump.

[Brianmoooore]

Oil travels from the block to the head by flowing up the space surrounding the head bolt in this area.

[Avinit4]

Torque-in the head down was easy enough when the block was in the car, but doing it with block out the car on a wheeled trolley was a nightmare. So its possible I messed up doing them!
Could the head bolt in that area being insufficiently tightened cause oil to leak from there?
If no then what else would cause oil to leak from that area?
If yes would I be right to conclude the only way to remedy correctly would be to replace all headbolts in the required order? Thanks for your help

[Andyboy]

M20's didn't have stretch bolts in 1986 - they began to be fitted in late 1988. A 1986 car will have had 17mm hex bolts and these must never, ever be re-used. They must not the angle tightened either. They have a nasty habit of shearing the heads off for no apparent reason and these can get punched through the head by a cam lobe. Oil leaks can be an oil filler cap seal, incorrectly tightened cam cover, cam oil seal or the four D seals.

[Avinit4]

Thanks Andyboy.... I used new headbolts but had the difficulty doing them up explained above. I think you may have missed out or used wrong word in this sentence..... 'They must not the angle tightened either' ...... because I don't understand it?

Theres no oil above the head to block joint and apparently only place can leak from there is exhust side about 3rd way along the joint as Brianmoore pointed out above. I guess he hasn't had time to reply to what I asked about cause & remedy or my question is stupid because answer is obvious to him? I don't know but all I can do is change the headbolts, at least this time it wont be a nightmare doin them up.. ... cheers

[daimlerman]

Andy means that the original,hex headed,bolts must not be re-used or angle tightened.You must replace these with the later,torx head stretch bolts,these need tightening as described by Brian above.

[Avinit4]

I hav always used new head bolts and tightened exactly how Brian says to above. But now I understand what Andy was saying...thanks.daimierman

[daimlerman]

Is your oil leak a torrent or the odd drop?

[Avinit4]

Its not the odd drop and I dont get massive oil patch on floor but if engine left running and car stationary then would be small oil patch on floor... its defo to much to ignore!

[Brianmoooore]

The seal of the head gasket around this particular bolt is marginal at best - it's a common place (amongst about twenty others) for M20s to leak.
Any distortion of the head or block face may exasperate the problem.

[Avinit4]

OK thanks Brian...... While doing the crankshaft I thought may as well recon the Head so is good as new as you can see

http://i494.photobucket.com/albums/rr30 ... 9d5d0f.jpg

I also used a quality sealant, it didn't leak straight away but now its losing to much to ignore, ive replaced cam seal etc again to be sure so I must have messed up torque-in the Head down!
At the time I thought I had for reason given above.
I need to reset one of the valve gaps so will replace headbolts 1st as much easier to do with engine in the car. Live and learn as they say..... Thanks to everyone for your input, much appreciated...

[daimlerman]

So assuming that the head face was skimmed up,your problem is either the block face or a gasket that is not seated properly.

[Avinit4]

Thanks for doin the pic, it wont work like that for me. Anyway yes the head was skimmed and there was no issue with the block before the re-build. I had the problem with the Headbolts explained above which leads me to conclude thats why the Head isnt seated properly.

I'm not intended to remove the Head, I intend to losen and remove headbolts in reverse sequence and imediately replace with new headbolts but this time will be able to torque correctly.
And hopefully that will remedy the problem.

To clarify, I am right to think that incorectly torqued headbolts can cause the head and inturn the gasket not to be seated corectly because of un-equal pressure from the head?
If I never had the nightmare putting the headbolts in, which involved the torque bar jumping a few times in addition to whole engine turning, plus my peice paper showing the 90 degrees could easily have moved at same time....... then I wouldn't think thats the cause thats resposible for gasket not being seated corectly. Do you agree thats possible or are you saying its not possible so I need to remove the head? cheers

[daimlerman]

For the cost of a set of bolts and a gasket,I would be inclined to pull the head and try again.
Whilst the head was off,I would ensure that the block face was surgically clean.

But remember,M20 is really a 50 year old engine design,built when 20w/50 oil was the best available,and little dribbles were more acceptable than they are today.
I run three cars,two E30's,one with a 2.7 M20,the other with an M50 conversion,these two are light years apart regarding oil consumption and dribbles.
The third is a Nissan Micra 1.4,that struggles to dirty it's oil over a 9k interval,despite being eleven years young!

[Avinit4]

I've just purchased head-bolts. Prior to rebuild there was no oil leak and its never burned oil in the 10yrs or more I had it.
The Block face was 100% surgically clean: It had been put into a steam jet wash machine that the engeneering place that was doing the head for me has. So defo was surgically clean when rebuilt.

I have to do this in the road so am very reluctant regards taking the head off because it takes me ages to ensure both surfaces are surgically clean, so becomes a much bigger and longer job than just replacing the head-bolts so can re-torque the Head. Because replacing the Headbolts is so much easier and will take a fraction of the time it will take to replace the gasket as well I'm thinking its worth taking the chance on just doing bolts first and if doesnt work then will do again with gasket. Maybe if I wasn't doin the work in the road I'd think differently?
To do the gasket and clean surfaces will take me a minimum of 2 days more than doin just the bolts, assuming good weather that is. So for the price of set of bolts in addition to knowng the current bolts are incorectly torqued I feel its more practical to remove old bolts and immediately replace with new ones so no need to remove manifolds etc. Does that make sence or am I bein stupid to even think this could solve the problem? Sorry for goin on bit, just tryin to give you complete picture of situation/circumstances....

[daimlerman]

IMO;
Just removing one bolt at a time and replacing with another is a waste of time.If the head is not seated correctly,just swapping bolts around is unlikely to make any difference.

If it were I,I would lift the head complete with manifolds,check the faces,replace the gasket and try again.

Good on you if you are working at the kerb,makes every job more difficult.

Just a thought;
Is this an engine that has been removed,re-built,re-installed by another?
May be worth asking them to fix it?

[Avinit4]

I personally, physically and single handedly replaced crankshaft and fitted new everthing else as well, including new piston rings while I was there and yes I did get the barrels professionally honed, I also had the valves reground by machine, apart from that everything else was me.

Obviously 2 messages back when I wrote......

I intend to loosen and remove head bolts in reverse sequence and immediately replace with new head bolts but this time will be able to torque correctly.

I should have included...... 'once all bolts are removed' immediately replace with new ones. But I mistakenly thought it was obvious I didn't intend doin it one bolt at a time for the reason you state. My mistake for not writing clearly enough. sorry bout that

So to clarify, I would firstly loosen each bolt by 90 degrees in reverse sequence untill all are loose and then remove. So incorrectly torqued set of bolts and probable cause of head not being seated correctly has gone.

I would then fit new set bolts to hand tight in correct sequence till all bolts in place.... I would then torque each bolt in sequence to 30psi or what ever it is and then I would do the 90 degree bit etc.....

Maybe I should have wrote I will remove set of bolts using correct removal procedure and then immediately replace with set of new bolts following the correct installation procedure.
The head should now be seated correctly or at least a high probability of being seated correctly, yes no?

[daimlerman]

I would still be tempted to replace the gasket,afterall,this is the bit that provides the final seal between the block/head.And will offer the chance to double check that no debris is present.

At the end of the day,it's your engine and your choice.
All the zone can do is offer up advice that is backed up by practical experience!

[Avinit4]

And I appreciate the zone's help very much....... I'm just having trouble conveying my situation correctly in writing.

I fully understand where your coming from, but im 50yrs old working alone so even if theres only a 25% chance of success without doing the gasket then I'd prefer to take that chance because the head with manifolds is heavy to do in the road so better to remove manifolds first.

So 25% chance of success is worth while to avoid all that, which is why because I know current head bolts are incorrectly fitted I'm asking if just replacing head bolts in theory at least will ensure head seated correctly.

Obviously if doesnt work then I will do again in the way you advise.

I'm sorry if I'm coming across as ungrateful as not intended that way