What's the best way to check cylinder head valves for leakage? - PeachParts Mercedes-Benz Forum

lietuviai · #1 06-24-2007, 08:32 PM

What's the best way, without taking a head to a machine shop, to check if the valves leak? I have a couple of heads off of 617's that I suspect that some of the valves leak. After testing the compression on one when it was still on the block lead me to think that. After adding oil to the combustion chambers, no increase in compression was achieved on a couple of the cylinders.
I poured a little Marvel Mystery oil into all the intake and exhaust ports of the removed heads to see if any of the valves leak. There were a few that did indeed leak.
Am I going about it in the right way by doing this way or will valves leak any way by adding MM oil to them?

vstech · #2 06-24-2007, 08:39 PM

is the cam still on the head?
if the valves were recently adjusted, but not driven much after, they could still leak if they are good. I would remove the springs and visually inspect the valves for grooves and cracks/burns and such. valve lapping compound is affordable, and pretty simple to do, if no cracks or burns are evident.
spring pressure should hold back fluid if the valves are good.
http://www.v6z24.com/howto/valvelapping
http://www.powrgrip.com/cgi-bin/powrgrip/V1275.html
http://www.goodson.com/store/template/product_display.php?NID=61
here is a link to a forum discussion of valves/ and lapping etc...
http://cartalk.com/board/showthreaded.php?Cat=0&Number=328489&page=0&vc=1

#3 06-24-2007, 08:45 PM

Leak down test.

http://www.xs11.com/tips/misc/misc3.shtml
http://en.wikipedia.org/wiki/Leak-down_tester

vstech · #4 06-24-2007, 08:48 PM

Lance, that's not really an option with the head off the motor...

lietuviai · #5 06-24-2007, 08:50 PM

No, both of these heads are off their engine blocks. I haven't looked at the valves nor seats yet. I only have a lever type valve spring tool to take valves apart, the type that takes advantage of a rocker arm stud as it's fulcrum. I'm not sure one of these would work to remove valves on a 617 head and even less likely to reinstall the valves.

#6 06-24-2007, 08:53 PM

Quote:

Originally Posted by vstech

Lance, that's not really an option with the head off the motor...

Ok. I thought the original idea was to prevent the need to remove the head.

lietuviai · #7 06-24-2007, 08:54 PM

No, one head was off already and the other I pulled after finding some bad compression results on the other engine.

larry perkins · #8 06-24-2007, 08:56 PM

why dont you try a real simple test, remove the cam shaft, lay the head with valve stems up,place paper towels under head,fill the ports up say about 1/4 in with fluid,if the valves leak the fluid they are bad.
larry perkins lou ky

Stevo · #9 06-24-2007, 08:57 PM

When I did a valve job on my 616 head (under the watchful eye of my import indy buddy) I was told to fill the ports with solvent and leave it for a few hours, which is what you did. You might try just lapping them. Then try the "solvent soak", Whata ya got too lose

lietuviai · #10 06-24-2007, 09:01 PM

Quote:

Originally Posted by larry perkins

why dont you try a real simple test, remove the cam shaft, lay the head with valve stems up,place paper towels under head,fill the ports up say about 1/4 in with fluid,if the valves leak the fluid they are bad.
larry perkins lou ky

That's kind of what I've already done using MM oil. See post #1.
Should I try something a little less penetrating?

lietuviai · #11 06-24-2007, 09:02 PM

Quote:

Originally Posted by Stevo

When I did a valve job on my 616 head (under the watchful eye of my import indy buddy) I was told to fill the ports with solvent and leave it for a few hours, which is what you did. You might try just lapping them. Then try the "solvent soak", Whata ya got too lose

That sounds like a good idea as I've got nothing to lose at this point.

larry perkins · #12 06-24-2007, 09:10 PM

folks you had better read about valve laping,big mistake.
just my opinion
larry perkins lou ky

Stevo · #13 06-24-2007, 09:32 PM

Quote:

Originally Posted by larry perkins

folks you had better read about valve laping,big mistake.
just my opinion
larry perkins lou ky

Whats the deal? not a good idea??

lietuviai · #14 06-24-2007, 09:45 PM

Quote:

Originally Posted by larry perkins

folks you had better read about valve laping,big mistake.
just my opinion
larry perkins lou ky

Any sources you can cite? I'd really like to read up if there's something to look out for.

Cervan · #15 06-25-2007, 12:36 AM

remove the head pour a solvent over the valves and put pressurised air into the exhaust and intake of each cyilinder. you will see where the bubles are coming from.