reas4516
Registered Member
Hi all,
I am recently a new member and I am humbly approaching everyone's years of experience for some insight, before I set my truck on fire. I bought an 85 3/4 4X4 Chevy from California a few years back (I live in Michigan) that was completely rust free to build an off road rig. All I knew was that it was basically bone stock with a 350. The truck had either 97,000 miles or 197,000, not sure, most likely the ladder. The motor was running but leaked from a couple different locations so I pulled it to rebuild. Here is the sequence of events that followed:
I tested the compression first and found close to 150 PSI in all 8 cylinders.
We began teardown of the motor and as best as we can tell at some point someone took this motor apart and installed a short block and reused the entire top end. The heads were in rough shape with alot of build up but the cylinder walls were still within stock spec and had nice cross hatching pattern still. There seemed to be quite a few oil leaks (rear main, intake, fuel pump plate).
Based on this, we just "warmed it over" with new fel-pro gaskets, oil pan, timing chain, truck cam, lifters, pushrods, heads, oil pump, fuel pump, intake, and carb.
During the rebuild we noticed some signs that maybe the motor got a little hot. The rear main seal was browned and brittle but we checked all the bearings and everything looked fine.
After the motor was re-installed I put a suspension lift in just in time for hunting season and starting driving it. I quickly found it was leaking oil like a sive from the rear of the motor but didn't have time to fix it until after the season.
This spring I started troubleshooting figuring it was a screwed up rear main, I put dye in the oil and using a black light found that the oil was definetley leaking out of the rear main and spraying everywhere (it was dripping off the oil pain, starter, and bell housing cover).
I pulled the t-case, tranny, and cross member out to get access to the back of the motor. I verifyed that the oil was not coming from the back of the heads at all and also that the cam plugs weren't the leak.
I had a mechanic friend come over and we did another rear main seal (this time with a replacement that has a relocated lip seal for a motor with some groove wear on the crank). He was just there to make sure that I was doing it the proper way again.
So I put it all back together and drove it quite a bit around town doing lots of summer errands, but never had to get it up over 30 mph or higher RPM. It did not leak at all at this point.
Now hunting season is back up and I am driving it up to 70 mph and getting the RPM's up (TH400). I got home after my first time out and there was oil everywhere! Rear main again!
So after some investigation, it doesn't leak at low rpm, low speed. During high speeds and high RPM it spews oil everywhere, leading me to believe I might have high crankcase pressures forcing oil past the seal????
I checked my breather and it still flows and I also replaced my PCV valve and validated it has vaccum. My oil pressure is decent and doesn't run low at all. I know I did not screw up this rear main install again, I have done quite a few of them and never had one leak.
One idea is to rig up some kind of pressure gage on the dipstick tube to get a reading on crankcase pressures during high RPM's... if that is even a direction you guys think I should go.
I am at a loss and ready to just burn my truck down... I could use any help, direction, and troubleshooting suggestions anyone has. Thank you so much in advance for your time.
Jordan
I am recently a new member and I am humbly approaching everyone's years of experience for some insight, before I set my truck on fire. I bought an 85 3/4 4X4 Chevy from California a few years back (I live in Michigan) that was completely rust free to build an off road rig. All I knew was that it was basically bone stock with a 350. The truck had either 97,000 miles or 197,000, not sure, most likely the ladder. The motor was running but leaked from a couple different locations so I pulled it to rebuild. Here is the sequence of events that followed:
I tested the compression first and found close to 150 PSI in all 8 cylinders.
We began teardown of the motor and as best as we can tell at some point someone took this motor apart and installed a short block and reused the entire top end. The heads were in rough shape with alot of build up but the cylinder walls were still within stock spec and had nice cross hatching pattern still. There seemed to be quite a few oil leaks (rear main, intake, fuel pump plate).
Based on this, we just "warmed it over" with new fel-pro gaskets, oil pan, timing chain, truck cam, lifters, pushrods, heads, oil pump, fuel pump, intake, and carb.
During the rebuild we noticed some signs that maybe the motor got a little hot. The rear main seal was browned and brittle but we checked all the bearings and everything looked fine.
After the motor was re-installed I put a suspension lift in just in time for hunting season and starting driving it. I quickly found it was leaking oil like a sive from the rear of the motor but didn't have time to fix it until after the season.
This spring I started troubleshooting figuring it was a screwed up rear main, I put dye in the oil and using a black light found that the oil was definetley leaking out of the rear main and spraying everywhere (it was dripping off the oil pain, starter, and bell housing cover).
I pulled the t-case, tranny, and cross member out to get access to the back of the motor. I verifyed that the oil was not coming from the back of the heads at all and also that the cam plugs weren't the leak.
I had a mechanic friend come over and we did another rear main seal (this time with a replacement that has a relocated lip seal for a motor with some groove wear on the crank). He was just there to make sure that I was doing it the proper way again.
So I put it all back together and drove it quite a bit around town doing lots of summer errands, but never had to get it up over 30 mph or higher RPM. It did not leak at all at this point.
Now hunting season is back up and I am driving it up to 70 mph and getting the RPM's up (TH400). I got home after my first time out and there was oil everywhere! Rear main again!
So after some investigation, it doesn't leak at low rpm, low speed. During high speeds and high RPM it spews oil everywhere, leading me to believe I might have high crankcase pressures forcing oil past the seal????
I checked my breather and it still flows and I also replaced my PCV valve and validated it has vaccum. My oil pressure is decent and doesn't run low at all. I know I did not screw up this rear main install again, I have done quite a few of them and never had one leak.
One idea is to rig up some kind of pressure gage on the dipstick tube to get a reading on crankcase pressures during high RPM's... if that is even a direction you guys think I should go.
I am at a loss and ready to just burn my truck down... I could use any help, direction, and troubleshooting suggestions anyone has. Thank you so much in advance for your time.
Jordan
