Create an account Home  ·  ·  Forums  ·  ·  Articles  ·  ·  Downloads  ·  ·  Photo Gallery  
Login
Nickname

Password

Don't have an account yet? You can create one here.

Navigation
· Home
· Article Archive
· Article Submit
· Downloads
· FAQ
· Forums
· Members List
· Photo Gallery
· Private Messages
· Web Links
· Your Account

Search Articles



Forums

Wiper motor...which is the correct one?
Lead additive, one more question.
M31C mount with or without replica weapon
Backfire and Hesitation
Wanted: Steering column and shaft for M38-1952, or late CJ2A
2024 CT. MILITARY VEHICLE SHOW AND FLEA MARKET- JUNE 15,2024
Brake Line
How to link full size photos in posts
Clutch release bearing support cast tab for return spring
T90 case replacement required?

Willys M Jeeps Forums


willysmjeeps.com :: View topic - Low compression
 Forum FAQForum FAQ   SearchSearch   UsergroupsUsergroups   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Low compression
Goto page 1, 2  Next
 
Post new topic   Reply to topic    willysmjeeps.com Forum Index -> Technical Knowledge Base
View previous topic :: View next topic  
Author Message
Bobber
Member


Joined: Feb 09, 2014
Posts: 178
Location: Tri Cities, Washington

PostPosted: Fri Feb 23, 2018 5:35 pm    Post subject: Low compression Reply with quote

I've been noticing the loss of power in going up residential hills in my neighborhood. So I warmed up the 1952 M38, 24 volt, all stock Jeep. Pulled all the plugs out and inserted the compression gage, opened the throttle and cranked till the needle stopped. What I found was 80,80,0-5,55 lbs. On number three there just was no resistance. Sad .A little back story..... I asked a Gentleman to take a look at it about 5 years ago. He said he put in new rings and gaskets in it and it ran what I thought was great. Never faltered any unless I did something wrong to cause it.
Now here we are. I'm not sure what to look for or what to recognize when I open the motor up. I have read about broken rings, valves not closing. What should my next step be?

Thanks in advance.

Rusty, I moved your post here to our technical board since it is not considered an ongoing project jeep record type post. Wes K
_________________
Rusty, 1952 M38, Koenig hard top.
Back to top
View user's profile Send private message Send e-mail
wesk
Site Administrator
Site Administrator


Joined: Apr 04, 2005
Posts: 16225
Location: Wisconsin

PostPosted: Fri Feb 23, 2018 11:32 pm    Post subject: Reply with quote

It's time for you to open the engine manual and follow the troubleshooting charts. It is not time to pull the head yet.

As a starter the next thing I do is a differential compression test. If you do not know what this test does, or how it is done or what tester you use then it's time google "Differential Compression Test" and follow the data you find.

It's quite simple and will point you at the culprit quickly.
_________________
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
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Bobber
Member


Joined: Feb 09, 2014
Posts: 178
Location: Tri Cities, Washington

PostPosted: Sat Feb 24, 2018 9:31 am    Post subject: Reply with quote

Will do.
Thanks
_________________
Rusty, 1952 M38, Koenig hard top.
Back to top
View user's profile Send private message Send e-mail
Bobber
Member


Joined: Feb 09, 2014
Posts: 178
Location: Tri Cities, Washington

PostPosted: Sat Feb 24, 2018 1:38 pm    Post subject: Reply with quote

This is what I have done and found out. I didn't have a differential pressure tester. I put the cylinders at TDC when I checked each cylinder with air. What I did find is the air blows back into the intake side of the motor on Cylinder 3 and 4 with little or no resistance. Cylinder 1&2 leaked the air so little I couldn't tell in which direction. I read Page 72 in the TM 9 8012, I have more than 20 psi variation. It didn't give any direction to go other than to notify ordnance maint. personnel. Which Manual to next?
_________________
Rusty, 1952 M38, Koenig hard top.
Back to top
View user's profile Send private message Send e-mail
wesk
Site Administrator
Site Administrator


Joined: Apr 04, 2005
Posts: 16225
Location: Wisconsin

PostPosted: Sat Feb 24, 2018 10:13 pm    Post subject: Reply with quote

You have either two stuck open intake valves or a head gasket leak between those two cylinders. First pull the side valve cover and compare all four pairs of valve operations. Then pull the head.

Get yourself a copy of the civvy service manual which offers more than a referral to the motor pool. SM 1002 is a good start:



Link to PDF copy.
http://48cj2a.com/images/manuals/UniversalServiceManualForJeepVehicles.pdf
_________________
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
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Bobber
Member


Joined: Feb 09, 2014
Posts: 178
Location: Tri Cities, Washington

PostPosted: Sun Feb 25, 2018 12:14 am    Post subject: Reply with quote

That's what I did this afternoon. I've done some reading in a civvy manual and followed the trouble shooting area. I removed the intake/exhaust manifold, valve cover. I was hoping for a broken spring or something obvious, nothing jumps out at me. Tomorrow I'll remove the head. I did notice some water corrosion between cylinder 3 & 4 between the head and block. Didn't see that till I removed the intake and exhaust mans.

Sure glad I used antisieze on the intake/exhaust nuts.

What about the 80 PSI from cylinder 1 & 2? 80 PSI it's a far cry from 135.
Before I removed manifolds I did manage to get 25 psi on cylinder 3 and 75 psi on cylinder 4. 1 & 2 are still close in psi.
More to come tomorrow.
Thanks
_________________
Rusty, 1952 M38, Koenig hard top.
Back to top
View user's profile Send private message Send e-mail
wesk
Site Administrator
Site Administrator


Joined: Apr 04, 2005
Posts: 16225
Location: Wisconsin

PostPosted: Sun Feb 25, 2018 1:32 am    Post subject: Reply with quote

Pressurize #1 & 2 cyl's and see where the air hisses from before you pull the head. Don't forget to listen for air blowing into the oil sump past the rings. Just pull the dipstick out and place your ear close to the top of the tube. If you do hear a loud hiss in the sump then squirt oil on top of the pistons and recheck compressions. If they improve (air hiss is lower) then the 80 is from worn rings/bores.

Compressions tests are meant to be done with the engine at normal operating temp and the carb throttle valve & choke plates wide open.
_________________
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
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Mike_B
Member


Joined: Dec 10, 2017
Posts: 336
Location: Southern Maryland

PostPosted: Sun Feb 25, 2018 11:30 am    Post subject: Reply with quote

You could have carbon build up on the valves. In the past I've poured water (slowly) down the throat of the carb on a fast idle running engine to steam clean the valve and pistons, hard to do now that it's apart.

Mike B. Smile
_________________
Mike B
1953 M38A1 Brush Truck
1952 M38
1951 M100 Trailer
Back to top
View user's profile Send private message
Bobber
Member


Joined: Feb 09, 2014
Posts: 178
Location: Tri Cities, Washington

PostPosted: Sun Feb 25, 2018 10:01 pm    Post subject: Reply with quote

Air coming from crankcase, pulled head off. Carbon build up on pistons not much carbon build up on valves. No.3 cylinder valves looked a lot cleaner than the rest ( less carbon). So since I'm here, I've not rebuilt this motor so I'm going to do it. Got the civvy manual out going line by line on disassembling. It just kept getting slower and slower down the road. Best I could do on the flat is about ~45.
I have a picture of the pistons but can't remember how to get it here on this post. I have it in my album, I tried opening the album in another window and then tried to copy it. Just not sure now.
_________________
Rusty, 1952 M38, Koenig hard top.
Back to top
View user's profile Send private message Send e-mail
Bobber
Member


Joined: Feb 09, 2014
Posts: 178
Location: Tri Cities, Washington

PostPosted: Sun Feb 25, 2018 10:19 pm    Post subject: Reply with quote

I got here using an outside way. My kid helped me so I don't know. But here is the block. You can see I rubbed the valves with my finger.
_________________
Rusty, 1952 M38, Koenig hard top.
Back to top
View user's profile Send private message Send e-mail
wesk
Site Administrator
Site Administrator


Joined: Apr 04, 2005
Posts: 16225
Location: Wisconsin

PostPosted: Sun Feb 25, 2018 11:02 pm    Post subject: Reply with quote

Looks like two head gasket leak areas and a head & block that need resurfacing. #3 looks like it has been water injected for a while looking at the piston.



Here are the instructions for how to link a photo in your album to your post:
http://www.willysmjeeps.com/v2/modules.php?name=Forums&file=viewtopic&t=8670
_________________
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
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Bobber
Member


Joined: Feb 09, 2014
Posts: 178
Location: Tri Cities, Washington

PostPosted: Sun Feb 25, 2018 11:28 pm    Post subject: Reply with quote

Because I have no idea, how does this happen? How do you prevent this?\
Thanks for information.
_________________
Rusty, 1952 M38, Koenig hard top.
Back to top
View user's profile Send private message Send e-mail
wesk
Site Administrator
Site Administrator


Joined: Apr 04, 2005
Posts: 16225
Location: Wisconsin

PostPosted: Mon Feb 26, 2018 8:40 am    Post subject: Reply with quote

For various reasons the mating surface of the head and block deform over the years and once the head gasket lacks a uniform sealing pressure across it's entire surface it will allow leakage of coolant, compression and intake/exhaust airflows to bridge parts of the gasket. The machinist resolve this issue at overhaul by reurfacing (re-machining) (or as often referred to as Decking) the mating surfaces to true them up.
_________________
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
Back to top
View user's profile Send private message Send e-mail Visit poster's website
4x4M38
Member


Joined: May 30, 2014
Posts: 3440
Location: Texas Hill Country

PostPosted: Mon Feb 26, 2018 10:39 am    Post subject: Reply with quote

If your block serial number is still stamped on the block by the water pump
and you have the block decked, be sure and make a note of the number
and get it restamped after machining if they remove it during the process
_________________
Brian
1950 M38
MC11481
http://www.willysmjeeps.com/v2/modules.php?set_albumName=album372&op=modload&name=gallery&file=index&include=view_album.php
Back to top
View user's profile Send private message Send e-mail
Bobber
Member


Joined: Feb 09, 2014
Posts: 178
Location: Tri Cities, Washington

PostPosted: Mon Feb 26, 2018 1:29 pm    Post subject: Reply with quote

Ya thanks, It's been decked before cause the serial number was gone when I got it. I hope there is enough to work with. Do you think that the head gasket being bad would cause the oil to always be dark. It seems like the oil was always dirty.
I have another block that still has the serial number on the water pump boss. It's from a 48 - 49 willys. Haven't opened it up, but the whole block is there minus the valves. Hopefully I won't need it. I saw they have NEW blocks for sale at Kaiser Willys for 1600 and change. Shocked
_________________
Rusty, 1952 M38, Koenig hard top.
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic    willysmjeeps.com Forum Index -> Technical Knowledge Base All times are GMT - 6 Hours
Goto page 1, 2  Next
Page 1 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

Powered by phpBB © 2001 phpBB Group
Forums ©

 



PHP-Nuke Copyright © 2005 by Francisco Burzi. This is free software, and you may redistribute it under the GPL. PHP-Nuke comes with absolutely no warranty, for details, see the license.