01 4.3 LT 4x4 - Oil Pressure Issues - Second Motor, Same Problem ???

Ok all, I'll try to make this story as easy to understand as possible.

2001 Blazer LT - Bought it from my dad with 100k miles on it for $200.00
Mint condition everywhere, just didn't drive. Dad said "I think the head gaskets are bad. Oh, and it hasn't had an oil change since I bought it." He bought it in winter 02, and I just got the thing in July. It has sat most of this time.

Towed it home, wouldn't start, pulled the air cleaner off to find this stuff that looks like chocolate pudding in the air breather. Took it off at the throttle body, and found that, it was in fact everywhere. It was water and oil mix, and was coming out of every known orifice the engine had.

Cleaned this crap out, new head gaskets, truck drove great.
The next week a clip holding an oil cooler line popped off, and lost oil pressure going down the road. As a matter of fact, I just lost all of the oil period. Fixed this on the roadside, bought some oil, drove home fine, just scored the cam bearings enough that I lost oil pressure when idling.

Decided to rebuild the motor. New cam, new crank, all new bearings, new Mellings oil pump, new head gaskets again, etc etc etc. Truck ran beautifully. However, drove it about a hundred fifty miles on a road trip two days later, lost oil pressure slowly until I had nothing. Stopped, let the motor cool, it started back up and had full oil pressure. Pulled off the interstate into a gas station, and it lost oil pressure again, this time suddenly. I could rev up the motor and get 5psi out of it at high revs, but 0 when idling.

Towed home, now working on a 90k mi salvage engine from a wrecked truck. Installed it, ran fine. Put almost a thousand miles on it no problem. Driving back from Springfield the other day it started gradually losing oil pressure. remembering the last time this happened, I shut the truck off and coasted to a stop. Let engine cool, started it up, same thing from that gas station, 5psi at high revs, 0 at idle. Shut it off and got a ride home. Went back that night, started it up, full oil pressure. Drove 10mi to town and as soon as I pulled it in my shop parking lot, it fell to 15psi..... ANY CLUE WHAT THIS MIGHT BE??? Possible crap left over in the oil cooler from the old engine grenading?

HELP!!

Bill - EAGLE AUTO

Could be a problem with the oil pressure sender or the dash gage, they are not known for their accuracy. Are you checking oil pressure with a manual gage or just the gage in the dash?

Could be a problem with the oil pressure sender or the dash gage, they are not known for their accuracy. Are you checking oil pressure with a manual gage or just the gage in the dash?

When the oil pressure gauge falls and the truck starts knocking, that would be a giveaway I think.

Did you replace the oil pump relief valve? If it sticks open, oil pressure is bypassed back into the oil pan. Pretty common problem on the 5.3L, (not so much on the 4.3L) and will cause oil pressure to drop like a rock. Could be that some of that "chocolate pudding" got in there and is binding up the valve.

Whats the common thing all engines have that has been reused on every engine? You most likely have the rad thats been reused, how about the oil cooler lines, along with the bypass at the remote filter (assuming its 4wd). It sounds to me like some sort of restriction. Could be the oil cooler in the rad, the cooler lines themselves, or even the bypass valve at the filter housing, your loosing pressure somewhere.

Whats the common thing all engines have that has been reused on every engine? You most likely have the rad thats been reused, how about the oil cooler lines, along with the bypass at the remote filter (assuming its 4wd). It sounds to me like some sort of restriction. Could be the oil cooler in the rad, the cooler lines themselves, or even the bypass valve at the filter housing, your loosing pressure somewhere.


I have reused the radiator and the filter housing, however the oil lines from the remote adapter to the filter housing are used lines that came with this engine, as well as the remote adapter. I am taking the radiator out in the morning and taking it to a nearby radiator shop to have it flushed and cleaned thoroughly. As for the remote filter housing, I am going to call the local salvages in the morning and see if I can find one, so that I will have lines and all with it (as well as the annoying little clip I lost this evening off of the radiator lines. I hate those.)

Here is a trick that I used when I lost my head gaskets on an 82 Olds and filled the oil pan full of coolant. I will also say this is a bit of a last ditch effort.

What I did was drain the oil and put on a cheap new filter. I removed ALL the spark plugs and pulled the coil wire out. Next I put a gallon of diesel fuel into the crank case and turned the engine over with the starter until the battery died. This pumps the diesel fuel throughout the system. Then, I drained the diesel fuel out put on another new filter and some cheap oil, connected the plugs, charged the battery, and started the engine. I let it run for 15 minutes and changed the oil and filter again. This seemed to clean the crankcase pretty good as the oil stayed a honey color for quite a while.