M38 engine leakdown test results

[JeepdaddyRC]

Have been chasing an assumed vacuum leak.
Took a closer look at the engine.

Appreciate your help interpreting the cylinder leakdown test:

#.....In psi...Out.psi....Loss.......Location of escaping air
1.......80........72........10%.......Oil fill tube
2.......80........30........62%.......Oil fill tube, tail pipe, #3 and #4 spark plug holes, antifreeze was pushed up in radiator
3.......80........68........15%.......Oil fill tube, #2 spark plug hole, antifreeze pushed up in radiator
4.......80........66........17%.......Oil fill tube

[RonD2]

.......for continuity to save from re-treading the same ground (and in two forums here and G503), this is a continuation of a 5-page thread to solve the same problem ---> http://willysmjeeps.com/v2/modules.php?name=Forums&file=viewtopic&t=13523

Did you also do a compression test? Results?
_________________
Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51

“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari

[wesk]

Your leakdown test offers much more info than a compression check. I have been in aircraft maintenance since 1966. That industry quit wasting time with compression checks during WWII and almost 100 % now use the leak down test only. The reason for the switch was labor time. Why do a compression check if when it shows an issue you must then do a complete leak down test.

[JeepdaddyRC]

Removed side cover with #2 cylinder at TDC. Findings:

- confirmed 0.016 intake and exhaust valve tappet clearance
- several more threads showing on exhaust valve tappet adjuster
- exhaust valve spring keeper is 1/4 inch higher than the intake spring - suggesting it is partially open?
- lowered the adjuster to insert screw driver blade between tappet and valve
- valve moves up freely but does not return to same level as intake spring keeper

Sprayed PB Blaster thru plug hole. Unclear what is holding it up,
Suggestions?

[wesk]

Time to pull the head.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

[JeepdaddyRC]

The head is off. To my surprise, the #2 exhaust valve is not stuck open.
Pistons stamped 0.40.
Is the head gasket compromised between #2 and #3 cylinders and to the water jacket?
Needs cleaning, but no visible cracks to naked eye.
Should head go to a machine shop for magnafluxing?
What else should i look for, or do, while head is off?
Thanks for your help Wes, couldn't do this without you!

[wesk]

It looks like you have severe pitting in three locations between #2 & 3 cylinders on your head which could cause your symptoms.


_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

[JeepdaddyRC]

They look like carbon deposits between #2 and #3 cylinders (square in photo). Blown head gasket?
The valves and pistons do not appear cracked, broken or burned - but I am no engine expert.
If you see a blown head gasket, and that could explain the symptoms, is first step reassembly and testing?
Do you like the Felpro or 7285B or MWM copper head gaskets?

[wesk]

I have used the copper sandwich for years. The only little issue is you must retorque after first run. Not a big deal but many people abandon proven old fashion reliability for new ideas.

Your first step is a thorough cleaning of the head and block mating surfaces and an accurate check of trueness (Flatness) with no dips whatsoever. The block will be a problem since most folks are too lazy to pull the studs, clean them up and reseal and re-install them.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

[JeepdaddyRC]

Blown head gasket between #2 and #3 cylinders and to the water jacket.
See pitting on block and adjacent edges of #2 and #3 exhaust valves where head gasket was blown.
The rest of the block, valves and pistons look ok. Machinist straight edge indicated block was flat. You can see the RMC serial number.
Is the pitting trouble?







[img]

[wesk]

You will need to use a sealant with whatever head gasket you choose to use weather the gasket manufactures calls for sealant or not since the pitting provides the starting point for erosion which ends in gasket damage. It was your cylinder head that showed the worse pitting. I hope you had the head resurfaced when they did the block deck? Post a photo of the mating surface of your cylinder head now.
_________________
Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

[JeepdaddyRC]

Important not to leave a thread hanging. Cylinder head back from machine shop. Head magnafluxed and decked. No cracks in head. Installed head with new copper sandwich gasket with sealant. Torqued to 60-65 ft lbs.

Repeat leakdown test confirmed no more leakage between adjacent cylinders, no more sound at carb or tailpipe, and coolant no longer pushed up in the radiator.

Still have a fuel delivery issue and will now return to that thread:
http://www.willysmjeeps.com/v2/modules.php?name=Forums&file=viewtopic&t=13523

[Pierre]

Nice, how many thousands were taken off the head ?
_________________
Pierre H.

full restoration in progress
1952 M38 MC60228

[JeepdaddyRC]

I don't know the exact amount removed, but the old-school machinist knows the L-134 ands stated he took off as little as possible.