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

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

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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

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Bob Smitter wrote:

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.

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wrote in message ...

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.

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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?

--
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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.

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

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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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
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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.

wrote:

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wrote:

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

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Bob Smitter wrote:

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.

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wrote in message ...

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.

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

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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

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wrote:

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.

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Bob Smitter wrote:

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

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

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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.

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

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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

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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:

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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.

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