West 1
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- Jan 20, 2023
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I have a 2003 GMC Yukon 5.3L with 130,000 miles on it. Developed a couple oil leaks, seems to be coming from the pan gasket. There is a little oil below the rear main seal but looks dry around the flex plate and torque converter.
Previously at 100,000 miles and 8 years ago I pulled the timing cover and installed a Melling M295 Oil pump and a new Oring. Doing this from the front the factory oil pan and gasket stayed in place, was good but has now developed small leaks. Not a lot but I hate oil spots on my driveway.
With the new Melling pump at 100,000 miles I had good oil pressure, 30 psi hot idle and 40-60 psi hot at RPM depending on what RPM you were running but oil pressure was a little less than before the new pump install? That always bugged me a little.
I have the Melling M295 Oil Pump in the truck, this pump comes with a standard Spring installed (as advertised) and 2 optional springs for lower or higher oil pressure come in the box. I believe Melling says the 3 springs offer 50, 60 and 70 PSI.
Since the pan was off I decided to go ahead and pull the timing cover again and change the pump pressure relief spring. I wanted better oil pressure at idle.
On removal I was surprised to find that the M295 had the lower pressure spring installed from the factory? It was supposed to have the middle pressure spring installed. Easy to tell which spring is which since they differ by length. Longer = more pressure.
I debated but decided to go with the longest spring. Fired it up tonight. Wow, cold start oil pressure was about 75 psi at idle! Fully warmed up idle oil pressure is still 65 PSI by my gauge in the dash. Formerly it was 30 PSI hot idle oil pressure.
If it was not so much work to go back and change it I would choose the middle length spring which I think would have me at 55 PSI Hot idle Oil Pressure. I wanted to post this so others might make a better decision than I did.
I should also share that when I did my Oil pump install we also did my buddy's truck, he had 270,000 miles on it and suddenly had zero oil pressure on start up. His truck motivated us to change pumps on both trucks at the same time.
At 270,000 miles his truck had 60 PSI hot oil pressure at idle, mine at 100,000 miles was below 40 PSI at hot idle? We did both pumps from the front to save time. It worked and was less time than pulling the oil pan off.
With the slightly lower oil pressure when I installed the new pump at 100,000 miles I was afraid maybe my engine bearings were starting to go bad but that is now ruled out, to have 65 psi at idle oil pressure the bearings have to be tight still so that is very good.
I will share that I had started using 10-40 synthetic to get the pressure up over 30 at idle and that is what is in it right now so I know I can cut back to a 5-30w now and oil pressure will come down maybe 5-10 PSI so I will do that but just wanted others to know what I found.
One more possible issue found on tear down. The Oring installed at 100,000 miles was the Melling supplied green O Ring which is recommended for the tapered pick up tube I found in my truck. On tear down the tube dropped right out when the bolts were removed. I did not have to pull to get the pick up out of the pump. The Oring was flattened by heat and time but it really only had 30,000 miles on it. This Time on install I used a Fel-Pro Red Oring hoping to get better seal. My guess is maybe the green Oring was weak from the start? The red new oring seals better? Oil pressure always built up quickly at start up in this truck even with the green O ring indicating the O Ring was sealing, was never slow to build start up oil pressure as I have seen on other trucks due to old hard orings.
The good news is Oil pressure is very solid now, the leaks in the oil pan gasket witnessed along both side rails are fixed. Bad news. There is a small drip from the Rear Main seal gasket which I had hoped was from the oil pan at the rear. Damn. The tranny will need to be removed to fix that one at a later date. It was leaving 3 small oil spots before it is down to only one small oil spot. More fun for a later date I guess. I hate oil spots. I hope this helps others or at least offers entertainment! Mark
Previously at 100,000 miles and 8 years ago I pulled the timing cover and installed a Melling M295 Oil pump and a new Oring. Doing this from the front the factory oil pan and gasket stayed in place, was good but has now developed small leaks. Not a lot but I hate oil spots on my driveway.
With the new Melling pump at 100,000 miles I had good oil pressure, 30 psi hot idle and 40-60 psi hot at RPM depending on what RPM you were running but oil pressure was a little less than before the new pump install? That always bugged me a little.
I have the Melling M295 Oil Pump in the truck, this pump comes with a standard Spring installed (as advertised) and 2 optional springs for lower or higher oil pressure come in the box. I believe Melling says the 3 springs offer 50, 60 and 70 PSI.
Since the pan was off I decided to go ahead and pull the timing cover again and change the pump pressure relief spring. I wanted better oil pressure at idle.
On removal I was surprised to find that the M295 had the lower pressure spring installed from the factory? It was supposed to have the middle pressure spring installed. Easy to tell which spring is which since they differ by length. Longer = more pressure.
I debated but decided to go with the longest spring. Fired it up tonight. Wow, cold start oil pressure was about 75 psi at idle! Fully warmed up idle oil pressure is still 65 PSI by my gauge in the dash. Formerly it was 30 PSI hot idle oil pressure.
If it was not so much work to go back and change it I would choose the middle length spring which I think would have me at 55 PSI Hot idle Oil Pressure. I wanted to post this so others might make a better decision than I did.
I should also share that when I did my Oil pump install we also did my buddy's truck, he had 270,000 miles on it and suddenly had zero oil pressure on start up. His truck motivated us to change pumps on both trucks at the same time.
At 270,000 miles his truck had 60 PSI hot oil pressure at idle, mine at 100,000 miles was below 40 PSI at hot idle? We did both pumps from the front to save time. It worked and was less time than pulling the oil pan off.
With the slightly lower oil pressure when I installed the new pump at 100,000 miles I was afraid maybe my engine bearings were starting to go bad but that is now ruled out, to have 65 psi at idle oil pressure the bearings have to be tight still so that is very good.
I will share that I had started using 10-40 synthetic to get the pressure up over 30 at idle and that is what is in it right now so I know I can cut back to a 5-30w now and oil pressure will come down maybe 5-10 PSI so I will do that but just wanted others to know what I found.
One more possible issue found on tear down. The Oring installed at 100,000 miles was the Melling supplied green O Ring which is recommended for the tapered pick up tube I found in my truck. On tear down the tube dropped right out when the bolts were removed. I did not have to pull to get the pick up out of the pump. The Oring was flattened by heat and time but it really only had 30,000 miles on it. This Time on install I used a Fel-Pro Red Oring hoping to get better seal. My guess is maybe the green Oring was weak from the start? The red new oring seals better? Oil pressure always built up quickly at start up in this truck even with the green O ring indicating the O Ring was sealing, was never slow to build start up oil pressure as I have seen on other trucks due to old hard orings.
The good news is Oil pressure is very solid now, the leaks in the oil pan gasket witnessed along both side rails are fixed. Bad news. There is a small drip from the Rear Main seal gasket which I had hoped was from the oil pan at the rear. Damn. The tranny will need to be removed to fix that one at a later date. It was leaving 3 small oil spots before it is down to only one small oil spot. More fun for a later date I guess. I hate oil spots. I hope this helps others or at least offers entertainment! Mark
