Oil leak through head gasket - tightening head bolts...

Have a question or want to start a discussion? Post it! No Registration Necessary.  Now with pictures!

Threaded View


I am going to tighten my head bolts as a possible easy fix for an oil leak
on a very high mileage 1990 325is.

It seems to be leaking between cyclinder 4 and 5.  The leak is on the
exhaust side.

One tech recommended tightening the 4 head bolts just in the area of the
leak.

Another tech recommeded tightening all of the head bolts, in the proper
sequence, uniformly.

Which is the better way to do it?????

I do not have the money to get my top end redone, so that is out of the
picture for now.

Thanks in advance.

- Ben



Re: Oil leak through head gasket - tightening head bolts...



Quoted text here. Click to load it

If this is what you will try, it is probably nest to torgue them all in
the proper sequence.  That way they will not be applying an
unbalanced force which could warp the head in a different plane.
Good luck deciding on a torque value since these are "stretch
bolts" which are torqued to a value, then a number of degrees.

Bob



Re: Oil leak through head gasket - tightening head bolts...


Bob Smitter wrote:
Quoted text here. Click to load it
I have owned 4 six cylinder E30 BMWs and they all leak oil from the
front of the engine ( cylinders 1 and 2 ). It has never been excessive
nor has it been a problem in terms of oil consumption. It is a little
unsightly and makes  a mess of the front of your engine but I have never
   bothered about it. I suspect you may have something similar. As one
reply said "be CAREFUL" that head is thin alloy should be treated
catrefully. Personally I would ignore it unless it becomes a problem.

Re: Oil leak through head gasket - tightening head bolts...



Quoted text here. Click to load it


I'm with Dave on this one. A bit of a mess on the side of the block is much
better than a warped head.




Re: Oil leak through head gasket - tightening head bolts...


Quoted text here. Click to load it


My 633 makes a mess on the side of the block alright, then it drips
down onto the exhaust manifold and when I come to a stop, smoke
plumes eminate from under the hood. I've redone that cover at the back
of the head and it no longer leaks but...

Has anybody had this? I've cleaned it thourouly several times
and looked for oil. No matter how much I rev the engine I
don't see any. Drive it for half a mile and there's oil
everywhere. I've changed the valve cover gasket.

Hep! WTF is this. Or how do I tell?


--
   Need Mercedes parts?   http://parts.mbz.org
Richard Sexton       | Mercedes stuff: http://mbz.org
We've slightly trimmed the long signature. Click to see the full one.
Re: Oil leak through head gasket - tightening head bolts...


Quoted text here. Click to load it


Have you checked all the engine crankcase breathers are clear? This is
often the reason for oil leaks when running you can't find at idle. Check
all rubber hoses etc are clear too - or simply replace.

--
*Beauty is in the eye of the beer holder...

    Dave Plowman         snipped-for-privacy@davenoise.co.uk           London SW
We've slightly trimmed the long signature. Click to see the full one.
Re: Oil leak through head gasket - tightening head bolts...


Quoted text here. Click to load it

That's certainly worth a try. Danke.

In return I present the happiest two seconds of my life, which took
place in this car two years ago.

I was driving on a deserted two lane highway in farm country. I had to
make a right soon and as I wa unfamiliar with the area having only
driven it once, I was not quite sure where.

I was stuck behind an old man wearing a hat with his blinkers on
doing like, 35 mph. Ihad had no oppertunity to pass. Suddenly I
did; hammered it and ripped past him. Before I even get back into
my lane I see my corner. I'm going way to fast to make it and in
and "oh well, I'll either die or have a helluva time" turned right.

The car turned right. Just like that. The road now turned sharply,
very sharlply to the left. As did the car. Like it was on rails,
or a slot car. I can honestly say I've never felt anything like that;
I've slid off the road in Italian sportscars with easier corners.

Not being a religous man I suddenly get religion and thank god for the
most interesting second of my life and could not imagine anything
nicer than this.

I look over to my left and see two young girls in bikinis jumping
on a trampoline waving at me. Oh. Dear. GOD.

Unless they change the age of consent I cannot imagine a more perfect
moment.



--
   Need Mercedes parts?   http://parts.mbz.org
Richard Sexton       | Mercedes stuff: http://mbz.org
We've slightly trimmed the long signature. Click to see the full one.
Re: Oil leak through head gasket - tightening head bolts...


Could be that the acceleration/deceleration is causing the oil to move to
the place where it's leaking.
You might try parking the car on an incline while you're trying to find the
leak.


Quoted text here. Click to load it



Re: Oil leak through head gasket - tightening head bolts...



Quoted text here. Click to load it

You're talking about a leaky valve cover gasket, the OP is asking about a
leaky head gasket. Huge difference.






Quoted text here. Click to load it


Re: Oil leak through head gasket - tightening head bolts...



Bob Smitter wrote:
Quoted text here. Click to load it

I agree, torque them in sequence. Without a torque spec, I'd see what
torque (defecting beam wrench works best for this) it takes to move the
first one 10-15 degrees, then set my click wrench to that value. Then
put it back together and see if it helped. If not, you might go back
next week and try another 10 lbs in the area of the leak.

Re: Oil leak through head gasket - tightening head bolts...



Quoted text here. Click to load it

I agree.


Less sure about this.  The bolts must surely still be in the area of Hooke's
law, otherwise mere thermal expansion and contraction of the [aluminium -
high cte] block would damage the [steel - low cte] bolts.

Maybe you slacken them off slightly (and evenly) and then retighten to the
specification plus a few degrees.  It is also possible that one or more of
them has become slightly loose.

Quoted text here. Click to load it

PS Bob, what about replacing them - feasible or a waste of money on a car of
this age & mileage?



Re: Oil leak through head gasket - tightening head bolts...



Quoted text here. Click to load it
You know, that might not be such a bad idea!  Complete sets of
bolts can be had for less than $20.  Then you just torque them
as specified.

Bob



Re: Oil leak through head gasket - tightening head bolts...



Quoted text here. Click to load it
IMO leave well alone unless your going to do the job properly. once you
remove head bolts you will run the risk of oil escaping into further area's
of the leaking head gasket (which might have previously been sealed) and
causing a bigger leak than you had in the first instance.
if its not a major leak just carry spare oil in your car and top up as
necessary until you are ready to do the job properly.
if your going to do anything, then just tighten them, dont slacken them off
until the head is ready to be removed.
Steve.



Re: Oil leak through head gasket - tightening head bolts...


Bob Smitter wrote:
Quoted text here. Click to load it

The only problem with that is the head gasket is already flattened and
hardened.  I'm not sure this would work *if* the problem even is the
head gasket...

Might be better off just doing the whole head gasket?

--
-Fred W

Re: Oil leak through head gasket - tightening head bolts...


Quoted text here. Click to load it

I was under the impression that they were torqued past the bolt's
elastic limit. Isn't that why they're single use?


--
Who needs a life when you've got Unix? :-)  
Email: snipped-for-privacy@unixnerd.demon.co.uk, John G.Burns B.Eng, Bonny Scotland
We've slightly trimmed the long signature. Click to see the full one.
Re: Oil leak through head gasket - tightening head bolts...



Quoted text here. Click to load it

Your're right, but they only go just into the plastic deformation area -
this is to allow for less accurate [factory] assembly and for relaxation of
the gasket after running.

It might be worth investigating whether the bolts in the failed area can be
replaced with non stretched ones.

OTOH I definitely follow the advice that if the oil leak is small and you
are not losing compression or water, then just top up.



Re: Oil leak through head gasket - tightening head bolts...



Quoted text here. Click to load it

Ooops - but you may have to retighten them after running in.

Quoted text here. Click to load it



Re: Oil leak through head gasket - tightening head bolts...


Before you start monkeying around with the head bolts you would be well
advised to make very very sure that it's not just leaking out of  the valve
cover gasket which is much more likely.  Get some solvent and clean the
surfaces around the valve cover joint and the head joint so you can tell
where it's leaking.  After cleaning the surfaces just run the engine while
you watch with a good light until you see the surface get wet.  Hopefully
you will find the leak to be in the valve cover joint.

If it turns out that your engine is really leaking through the head gasket,
the only 'proper' way of fixing it is to replace the gasket.  However, there
is a procedure prescribed in the Bentley Service Manual for replacing faulty
head bolts on these engines that were built up to April of '89 and that is
to remove, replace, and retorque the bolts one at a time.  You could try
this in an attempt to stop the leak although I can't really think of any
reason why it would work.  Headbolts do not become loose over time and
anything you do to disturb the gasket seems like it would only make things
worse.
Best of luck
Jack

There was a
Quoted text here. Click to load it



Re: Oil leak through head gasket - tightening head bolts...


  If it is in fact a leaking head gasket, the only way you are going
to fix it is by taking the head off of the car and replacing the
gasket (after ensuring that the head is not slightly warped as well).
Anything else you try is going to be a waste of time and possibly cost
more money. If you try to tighten the bolts, you run the risk of
breaking one in which case you'll be pulling the head anyhow. My
suggestion would be to obtain a top end gasket set, a new water pump,
a timing belt and tensioner and prepare to get your hands a bit dirty.
This can be done in a weekend fairly easy and if you can live without
the car for a few days, have the valves done while it's apart.

wrote:

Quoted text here. Click to load it

Re: Oil leak through head gasket - tightening head bolts...


If the oil is seeping, I'm not sure I'd do anything. If the oil is leaking
at a rate that requires atentiion, I'm not sure the head bolts will solve
the problem.

Having said that, the head is aluminum and the block is cast iron, so you
should be able to safely apply the torque wrench without fear of stripping
the bolt holes. I'd tighten all of the bolts in the proper sequence.





Quoted text here. Click to load it


Site Timeline