Compression Locked??

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Zfanch30

Junior Member
Joined
Jul 17, 2025
Posts
2
Reaction score
0
Location
Glasgow Ky
Ram Year
2018
Engine
6.7
Brother was driving down interstate and somehow his oil filter had almost worked its way all the way off. Truck shut off added oil and now when try to press button to start radio resets and all but no attempt to turn over. Worried it may be compression locked as I’m assuming it lost all oil pressure as loose as his oil filter had gotten. Not sure where to start to try and get this thing back on the road as we’re 12 hours from home on a job in Minnesota. TIA
 

4xdad

Senior Member
Joined
Feb 18, 2021
Posts
2,228
Reaction score
2,432
Location
Edmonton Alberta
Ram Year
2015 powerwagon
Engine
6.4
Lost all the oil Yikes not good. Probably not compression locked but seized. If it was compression/hydro locked you could remove the spark plugs and crank the motor to clear the cylinders.
 

4xdad

Senior Member
Joined
Feb 18, 2021
Posts
2,228
Reaction score
2,432
Location
Edmonton Alberta
Ram Year
2015 powerwagon
Engine
6.4
Unfortunately if it is hydrolocked and you tryed to start it you might have damaged the rods or other parts
 

Ken226

Senior Member
Joined
Mar 12, 2017
Posts
2,275
Reaction score
5,891
Location
Washington State
Ram Year
2013
Engine
Hemi
Brother was driving down interstate and somehow his oil filter had almost worked its way all the way off. Truck shut off added oil and now when try to press button to start radio resets and all but no attempt to turn over. Worried it may be compression locked as I’m assuming it lost all oil pressure as loose as his oil filter had gotten. Not sure where to start to try and get this thing back on the road as we’re 12 hours from home on a job in Minnesota. TIA

Typically the low oil pressure light will come on before the engine is toast. If he didn't notice or didn't stop driving and pull over, then the the engine is likely a goner. An engine that runs out of oil pressure doesn't compression lock. If not shut down immediately, the main and rod journals overheat, swell and friction weld themselves to the bearings, which then spin. I'm sure you've heard the term "spun a bearing" before. The engine seizes and is destroyed internally. He should try a socket/breaker bar on the harmonic balancer bolt and see if the engine will turn. If not, it is seized and he will need an engine.

If it does turn over, well, then it'll probably rattle and clatter horribly when it does start and he will still need a new engine. I'd be very surprised if an engine that was run out of oil and seized, survived the ordeal. I've heard of it happenning, but not on a modern engine.



I'd look at whoever did the last oil change as the person to blame.


Once of my coworkers recently had a similar experience.

Several of us at work noticed a really big, new oil trail in the parking lot and followed it around a couple laps to where it ended, under a brand new black Z71 Silverado. We fetched the owner, who had no idea. The oil filter was only threaded about halfway on from the Jiffy Lube oil change he had just got in Bellingham, WA the day before.
 
Last edited:

MrBonez

Senior Member
Joined
May 29, 2025
Posts
195
Reaction score
378
Location
Central Alabama
Ram Year
2008 Laramie Quad Cab
Engine
Hemi 5.7
Unfortunately if it is hydrolocked and you tryed to start it you might have damaged the rods or other parts
Same effect as it is with an old radial engine in an aircraft like an old WWII fighter or bomber.
Ever wondered why you'd see some guys walking in a line, grabbing the prop and spinning the engine by hand before it was fired up?

That was to get oil that ran down into the bottom cylinders out from the last time it had been ran. Hot oil in those (Or anything) always runs downhill and some settles into the bottom cylinders when it's shut down, that's why they have to do it before trying to start it again.

Turning it slowly by hand works it out the exhaust valves slowly so it doesn't "Hit" with liquid oil still in the cylinder when starting it. If it does the oil can't get out fast enough before damage occurs.
If it does, the engine is lunched on the spot because you can't compress a liquid.

I agree - Try to turn it by hand with a breaker bar and see if it even moves - If not, it's time for a new one.
 
Back
Top