Checking a for leaks

hans747

Well-Known Member
Joined
Feb 20, 2007
Location
Asheville, NC
Hi Everyone,

I know it's not a 4x4, but it its wrenching. And you guys are one of the best foums around for it. So here goes...

I'm working on 1992 BMW project that I picked up for $600. The inline six was showing signs of a bad headgasket, so i pulled the cylinder head this week. I read somewhere that you can do a rough and dirty test on the valves by turning the head over and filling the combustion chamber with WD40. I did that last night and all the cylinders held their fluid for about 2 hours.

Does that mean i can feel OK about just getting the head on this old beater resurfaced and slapping it back together?
 
When you take the head to the machine shop to have it resurfaced, ask them to vacuum check it. A lot of shops have a vacuum cup that sits over the chamber and they'll pump a vacuum on it and see if it holds.

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That brings up another point: what is a good straightedge that i can use? All the crap in my garage has been dropped so many times that I am not sute that I can trust any of it.
 
hans747 said:
That brings up another point: what is a good straightedge that i can use? All the crap in my garage has been dropped so many times that I am not sute that I can trust any of it.
Click to expand...
You can order an actual straight edge specifically made for checking blocks and heads from summit racing, or get a local machinist to put an edge on a piece of 1/4 or 3/8 stock.

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hans747 said:
The inline six was showing signs of a bad headgasket, so i pulled the cylinder head this week.
Click to expand...

What "signs" were you seeing?
HGs rarely go out on them, except for when overheated (mainly due to tiny reserve capacity)... which usually de-anneals the block, allowing the head bolts to pull out :eek:
 
Regardless of any of this, its a $600 92 BMW. Put a new headgasket on it and drive the piss out of it. Something else will break before the headgasket is a problem again :D
 
Caver Dave said:
What "signs" were you seeing?
HGs rarely go out on them, except for when overheated (mainly due to tiny reserve capacity)... which usually de-anneals the block, allowing the head bolts to pull out :eek:
Click to expand...
I was getting coolant in the cylinders and some low compression readings in some of the middle cylinders. I suspected that it had been overheated at some point. As we pulled the cylinder head off, we realized that someone had been in here before us: Aftermarket headgasket, the cams were timed a little wrong, signs of someone doing a DIY sandpaper resurface job on the cyl head.

Like I said, this is a $600 car. So I can see paying for a vacuum test and resurface job. If the valves are leaking, I will probably opt to either run them as is (if they are not bad) or clean/lap them myself.
 
Tim C said:
You can order an actual straight edge specifically made for checking blocks and heads from summit racing, or get a local machinist to put an edge on a piece of 1/4 or 3/8 stock.

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Click to expand...

You can also get a piece of precision ground flat stock from McMaster Carr. That's what I do for clutch pressure plates and flywheels.
 
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