Joined: Jul 10, 2018 Posts: 97 Location: Western Washington
Posted: Sat Aug 21, 2021 11:15 am Post subject: Seized engine - Advice needed
Background on the engine. It was rebuilt a a machine shop approximately 12 years ago for the PO. I have ran it 1365 mile with out issue. It has always had low oil pressure but I am running a 70 year old gauge and who know how old sender. I was happy to have oil pressure. Perhaps the oil pump took a crap.
I was driving it at highway speed recently and it just quit. No noise just quit like a light switch turned off. After trouble shooting thinking it was electrical, I found it to be seized. So far:
-tried to turn from the crankshaft nut- no dice
-ruled out clutch and/or transmission
-drained oil. Looked black but not shiny.
-dropped pan. Some particles there but not metallic. Some from the gasket material in the removal process.
-loosened the main bearings and tried to turn. No dice.
-cylinder bores look fine from below.
-do not see any tooth damage on the crank gear.
It could be in the cam or some where else that it is seized. Next steps and advice? I don't want to take the engine out if I don't absolutely have to. Thanks in advance. _________________ Rick Eades
1951 M38 & 1967 M715
Joined: Oct 02, 2014 Posts: 2010 Location: South Carolina, Dorchester County
Posted: Sat Aug 21, 2021 11:41 am Post subject:
Hi Rick,
Sorry to hear that. I think you'll eventually have to pull the engine anyway, but have you removed the oil pump and distributor? The oil pump drive gear meshes with the camshaft. Pulling them might reveal damage.
Was the radiator coolant level ok? Did you pull the spark plugs and they look ok?
Good luck! _________________ 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
Without removing the engine, my next steps would be to inspect the rod bearings that you can get to with the crank in its current position. And about all that is left, shy of pulling the engine, is removing the head for an inspection of the top end. _________________ '52 Dodge M37, '42 GPW, '48 FrankenJeep CJ2A/M38, '50 CJV-35(U), '51 M38, '42 WC-57 Command Car, '44 WC-51 Weapons , (2) M1941 Sperry 60" Anti-Aircraft Searchlights, John Deere M-gator, '44 White M3A1 Scout Car
Joined: Oct 02, 2014 Posts: 2010 Location: South Carolina, Dorchester County
Posted: Sat Aug 21, 2021 11:48 am Post subject:
Because it quit so suddenly (like a switch turned off), I was thinking (after pulling the oil pump) that it could be hydrolocked, as unlikely as that might be.
Removing the spark plugs is easy and should tell.
Keep us posted what you find. Good luck! _________________ 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
Joined: Nov 18, 2014 Posts: 128 Location: Connecticut
Posted: Sat Aug 21, 2021 3:08 pm Post subject:
Sorry to hear that you're having engine troubles Rick.
I personally can't see how a lack of oil pressure would seize the pistons dead in their tracks the way you described with all the other information given. A lack of oil could seize the crank or the cam, however I tend to believe you may have heard some indication of this before full engine seizure. You mentioned that you drained the oil and its quality didn't look peculiar, so I have to assume that the quantity that was drained also looked correct. With this in my mind, I would rule out an oil related issue.
You mentioned that you "ruled out clutch and/or transmission" as the culprit, and I would have to assume that you say this because you were able to safely coast to a stop after the engine seized. Once the engine locked up completely, holding the clutch pedal in or shifting to neutral would still allow you to coast to a stop, and this is how I'm assuming you ruled them out.
The only time I've ever seized an engine in the exact method that you described (highway speed, able to hold the clutch in and coast to a stop, sudden "it just quit like a light switch") was because the engine overheated and squeezed the pistons until they stopped dead in their tracks. If I were you, I would start with pulling the head off to see if the pistons locked up against the cylinder walls. At this point, you've already dropped the pan and loosened up the main bearing caps, it sounds to me like you've been inside the engine for a few minutes. What's a head gasket and a few more minutes to take the head off really going to cost?
Good luck Rick, keep us posted. _________________ Jake, Central CT
51 M38 s/n 35627
Joined: Jul 10, 2018 Posts: 97 Location: Western Washington
Posted: Sat Aug 21, 2021 6:42 pm Post subject:
I pulled the rod bearings and that was it. The rear one had metal in it. Small pieces in the oil pan too. I was able to turn the engine with a socket one I removed the rear cap and bumped it back and forth in 3rd.
Low pressure was 10 or less at times. I am running the 120 PSI gauge and 60 PSI sender.
I have to pull the engine now. Probably take it to the engine shop for a really good cleaning. Replace all bearings and clean up the crank for sure. _________________ Rick Eades
1951 M38 & 1967 M715
Time to install reliable modern direct reading mechanical oil pressure and water temp gauges that can be relied on. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Nov 18, 2014 Posts: 128 Location: Connecticut
Posted: Tue Aug 24, 2021 11:16 am Post subject:
Eades wrote:
I pulled the rod bearings and that was it. The rear one had metal in it. Small pieces in the oil pan too. I was able to turn the engine with a socket one I removed the rear cap and bumped it back and forth in 3rd.
Low pressure was 10 or less at times. I am running the 120 PSI gauge and 60 PSI sender.
I have to pull the engine now. Probably take it to the engine shop for a really good cleaning. Replace all bearings and clean up the crank for sure.
Well shucks, I stand corrected! I'm surprised you didn't hear anything leading up to the engine seizing. I would have always assumed low oil pressure for that length of time would have led to at least some God-awful engine noises.
To reiterate what Wes said, I guess it really does pay dividends to have gauges you can rely on. Without any noises or other indications, your engine gave you the silent treatment right up until she quit!
Sorry to hear about your engine Rick. _________________ Jake, Central CT
51 M38 s/n 35627
Joined: Jul 10, 2018 Posts: 97 Location: Western Washington
Posted: Wed Aug 25, 2021 9:26 am Post subject:
I'm going to bite the bullet and get a new oil pump. The bearings are trashed on the crank. Will take it to be machined. The bearings were .020 over. I will learn from my mistakes as it is an opportunity to make it reliable. _________________ Rick Eades
1951 M38 & 1967 M715
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