oil pressure help
Thread Starter
|
Lead Driver
Joined: Mar 2008
Posts: 7,182
Likes: 378
From: Near Los Angeles
oil pressure help
Hey guys--
I'm about at my witts end and need a bit of help. As you probably know, I recently rebuilt a hp 300. But with only 700 miles I have 38-39 psi at 60mph, with 15/40 oil. Yes, it bothers me A LOT.
Today I dropped the pan and removed one main and one rod cap. The bearings look good, with long pointed streaks of polished areas, and the rest of the bearing surface a dull lead color. No grooves or burns or copper showing. The new melling pump looked good too. All gaskets on the pickup were present, and the screen was not cloged. There was no debris to speak of in the pan.
However, I could see that the pump gears were wearing a groove in the pump cover plate. I could move the release plunger with a screw driver, and it made a squishing/pumping noise, so I assume it is good.
The cam bearings were snug in place, with no bearing surface sticking out. I just don't know what else to do at this point. But with that pressure--12--10 psi coming off the freeway, I don't know how much confidence I could have in this engine. If I had stayed with the 10/30 I had in it, then the pressure would probably be at failure point. I hate to put it back together without having solved the problem. It just kills me to have spent all that $ and to have such a problem.
If anyone can offer a bit of advice, it would be greatly appreciated.
Of course I will put a high volume pump back in it, but that is treating the symptom and not the cause.
I'm about at my witts end and need a bit of help. As you probably know, I recently rebuilt a hp 300. But with only 700 miles I have 38-39 psi at 60mph, with 15/40 oil. Yes, it bothers me A LOT.
Today I dropped the pan and removed one main and one rod cap. The bearings look good, with long pointed streaks of polished areas, and the rest of the bearing surface a dull lead color. No grooves or burns or copper showing. The new melling pump looked good too. All gaskets on the pickup were present, and the screen was not cloged. There was no debris to speak of in the pan.
However, I could see that the pump gears were wearing a groove in the pump cover plate. I could move the release plunger with a screw driver, and it made a squishing/pumping noise, so I assume it is good.
The cam bearings were snug in place, with no bearing surface sticking out. I just don't know what else to do at this point. But with that pressure--12--10 psi coming off the freeway, I don't know how much confidence I could have in this engine. If I had stayed with the 10/30 I had in it, then the pressure would probably be at failure point. I hate to put it back together without having solved the problem. It just kills me to have spent all that $ and to have such a problem.
If anyone can offer a bit of advice, it would be greatly appreciated.
Of course I will put a high volume pump back in it, but that is treating the symptom and not the cause.
Elder User
Joined: Apr 2004
Posts: 970
Likes: 3
I would suggest you borrow a pressurized oil tank to see where the leakage is, With the pan off you will find the problem real quick. Remove the sending unit and attach feed line too it. One place that is overlooked on these engines are the lifter bores. I have seen blocks that had the lifter bore sleeved to eleminate excess clearance. My two cents. kotzy
Thread Starter
|
Lead Driver
Joined: Mar 2008
Posts: 7,182
Likes: 378
From: Near Los Angeles
Problem found
I believe I found the problem. The oil smelled faintly of gasoline when I drained it. The oil gets thinned out so the pressure drops. Also, it wore the bearings. The book called for them to be from .oo08 to .0015. They were when built, but now, after only 700 miles, I have .002.
It was a good thing the bearing just slip out and are easily replaced.
After putting it back together today, I will try to determine whether the carb or the fuel pump is at fault. If it is the carburetor, it doesn't say a lot for Pony Carbs, who rebuilt it. With the carb, really there is only the float level to check.
It was a good thing the bearing just slip out and are easily replaced.
After putting it back together today, I will try to determine whether the carb or the fuel pump is at fault. If it is the carburetor, it doesn't say a lot for Pony Carbs, who rebuilt it. With the carb, really there is only the float level to check.
Postmaster
Joined: Dec 2006
Posts: 3,603
Likes: 10
From: Spokane, WA
I suggest a bad fuel pump...leaking back into the crankcase. Had that happen on the original engine in my truck and it took out the bottom end. Could smell gas but couldn't find a leak...until too late.
If it were the carb it would have to be leaking quite a bit to be washing down the cylinders and ending up in the crankcase. If the engine is not blowing black smoke at start up or while running I would discount the carb as being a problem.
If it were the carb it would have to be leaking quite a bit to be washing down the cylinders and ending up in the crankcase. If the engine is not blowing black smoke at start up or while running I would discount the carb as being a problem.
Thread Starter
|
Lead Driver
Joined: Mar 2008
Posts: 7,182
Likes: 378
From: Near Los Angeles
I suggest a bad fuel pump...leaking back into the crankcase. Had that happen on the original engine in my truck and it took out the bottom end. Could smell gas but couldn't find a leak...until too late.
If it were the carb it would have to be leaking quite a bit to be washing down the cylinders and ending up in the crankcase. If the engine is not blowing black smoke at start up or while running I would discount the carb as being a problem.
If it were the carb it would have to be leaking quite a bit to be washing down the cylinders and ending up in the crankcase. If the engine is not blowing black smoke at start up or while running I would discount the carb as being a problem.
Thread Starter
|
Lead Driver
Joined: Mar 2008
Posts: 7,182
Likes: 378
From: Near Los Angeles
I wanted to up date everyone, and say thanks to all who tried to help.
After pulling the pan, and smelling (faintly) gasoline, I checked the Carb and it did not leak after running. So that means the fuel pump. It is new, but I figure it is cheaper to replace while under warranty, than to loose bearings.
Also installed a hv oil pump. Whoa, minimal clearance! But there is clearance. It gives a big boost. I'm thinking the originally I had about 30 psi when hot at idle. Gas must of leaked into the crankcase, thinned the oil and that caused the extra clearance in the bearings, thus causing lower pressure.
I never had a mechanical pump do that before. It's almost enough to make you want to use an electric pump. I think I am also going to install an oil cooler with a fan. I like that Idea. Baja ready.
I also was very pleased to find out how easy it is to replace the bearings. If the radiator didn't have to come out, it would be a job that could be done in few hours. And a set of bearings is only about $50.00
After pulling the pan, and smelling (faintly) gasoline, I checked the Carb and it did not leak after running. So that means the fuel pump. It is new, but I figure it is cheaper to replace while under warranty, than to loose bearings.
Also installed a hv oil pump. Whoa, minimal clearance! But there is clearance. It gives a big boost. I'm thinking the originally I had about 30 psi when hot at idle. Gas must of leaked into the crankcase, thinned the oil and that caused the extra clearance in the bearings, thus causing lower pressure.
I never had a mechanical pump do that before. It's almost enough to make you want to use an electric pump. I think I am also going to install an oil cooler with a fan. I like that Idea. Baja ready.
I also was very pleased to find out how easy it is to replace the bearings. If the radiator didn't have to come out, it would be a job that could be done in few hours. And a set of bearings is only about $50.00
Thread
Thread Starter
Forum
Replies
Last Post
kr98664
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
15
Sep 27, 2016 01:21 PM
brain75
1948 - 1956 F1, F100 & Larger F-Series Trucks
31
Feb 5, 2016 06:01 PM
mark1986F150
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
10
Mar 13, 2015 08:52 PM
Jeff Fisher
Clutch, Transmission, Differential, Axle & Transfer Case
8
Aug 10, 2013 08:09 AM
F250F250F250
Clutch, Transmission, Differential, Axle & Transfer Case
10
Nov 17, 2012 07:40 AM
