C-12, low oil pressure

dirtcurt

Active member
We have a c-12 in a 99 T800. It started loosing oil pressure to the point of kicking a check engine light. Brought it to the shop and they put it on the computer and the electronic sensors are agreeing with the mechanical one that the pressure is low. The guy at the shop said dump some Lucas in it and run it. I really don't want to cause any more damage. Any Ideas?? The motor sounds fine.

I thought with 650K on it maybe put rods, mains, and a new oil pump in and see what that does. I don't know engine history except for the last 30K that we put on it.

Any other tests we could run?

Thanks for any ideas.
 

Truck Shop

Well-known member
Pull the oil filter and take it to a shop that has a filter cutter, see if there is metal in it. Next I would drop the pan and check the main and rod bearings. I doubt the oil
pump is failing. But for grins I would check oil pressure with another manual gauge first.

Truck Shop
 

Steve Frazier

Founder
Staff member
If you took an oil sample to your Cat dealer they could give you a good idea of what's going on. Ideally they like to have done the oil analysis on a regular basis to give you a base line but they should be able to tell you what kind of material they find in the oil such as main bearings, cam bearings, oil pump material, etc.....
 

rodneyp10

Member
If you took an oil sample to your Cat dealer they could give you a good idea of what's going on. Ideally they like to have done the oil analysis on a regular basis to give you a base line but they should be able to tell you what kind of material they find in the oil such as main bearings, cam bearings, oil pump material, etc.....
C12's broke some main bearing bolts. I would not run it until I got the pan off of it.
 

Goodysnap

Well-known member
All depends on how well its been maintained in the past. Bearings may buy you time if its a clunker and not worth putting a ton into. If it's been poorly maintained, good chance a rebuild would be in order to get any longevity out of it. The other oil control bearings are for the camshaft which are hard to inspect without pulling the cam. Once your down that far you might as well rebuild the thing while your in there.
 

Truck Shop

Well-known member
All depends on how well its been maintained in the past. Bearings may buy you time if its a clunker and not worth putting a ton into. If it's been poorly maintained, good chance a rebuild would be in order to get any longevity out of it. The other oil control bearings are for the camshaft which are hard to inspect without pulling the cam. Once your down that far you might as well rebuild the thing while your in there.
Agreed

Truck Shop
 

dirtcurt

Active member
I took the filter into Cat to get their opinion on things, "doesn't look too bad" was all I could get out of them. I had them send in an oil sample, that was 6 weeks ago and they are "still waiting" for the results. Needless to say, didn't need the truck just sitting around for that long, so we put rods and mains in it. They definitely looked worn when we pulled them out. The truck sounds nice and has decent oil pressure in the shop. Haven't had it out on the road yet. See how it goes when we do. I didn't want to stick a ton of money in this thing as it gets about 8-10K miles a year on it. Hope for the best.
 

Truck Shop

Well-known member
That's pretty unusual for cat to take that long on a oil sample. 3 to 4 day's would be normal. Good that the psi came up cold, warm it up and see what you have hot.

Truck Shop
 

dirtcurt

Active member
Put in the new bearings and ran it for the past couple weeks with zero issues. Done with it now till spring. Still waiting for Cat to get back to me with oil sample results. Needless to say I bought my parts from a different cat dealer. Beginning to think the 1st dealer didn't even send the oil sample in. Guessing i'm not a big enough customer for them to worry about.
 
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