No oil pressure at idle

[raff]

I bought a clean 2002 Explorer 4x4 XLT to fix up. The engine sounded like a diesel and had no oil pressure at idle after warming up. I began by researching threads here and changing out upper timing chain tensioners. I also removed lower oil pan and cleaned out metal shavings and one metal ear from the oil pickup. No luck. Then I dug into it and found broken left front cassette. Used the procedure here for changing out cassette alone without the timing tools, thank you! I did not replace the main guide and tension spring, however (Doh!) The procedure worked great but still no oil pressure. I then removed sway mounts, rack mounts, and 3 differential housing bolts to access and remove upper oil pan. I wound in new main bearings and replaced the oil pump. Still no oil pressure at idle, though I do not have to goose the throttle as much to get it to come up. The mains needed changing, no question.
if I keep the oil pressure up, ie the tensioners extended, the only noise remaining is that "spark knock" sound of the main chain. My next plan is to go back into the front timing cover and replace the guide and spring. Is that where
I'm losing pressure, at the oil port behind the guide? Any input from those experienced would be helpful and appreciated. And a happy Thanksgiving to all!

 

[Bobmbx]

Most likely your oil pressure relief valve is jammed open by a piece of plastic. At low RPMs, the valve is dumping enough oil back to the sump to prevent pressure from building in the system; this is also starving your engine of the oil it needs at those low RPMs. Once the RPMs increase, enough oil is being pumped to create the needed pressure. I believe the relief valve is a part of the oil pump itself.

I've never made this repair myself. I'm sure someone here has.

 

[Joe in NY]

The really scary part is that you are only building 5 psi of oil when you "have pressure" Ford logic:

Drivers are idiots. Especially those who buy fords... So instead of an actual pressure gauge it will do this: 5 psi or more gauge reads in the middle of "Normal". less than 5 psi gauge reads "L".

So really you have 0 psi and then barely 5 psi... Either way.. Motor sounds in very bad shape.

 

[Bobmbx]

The really scary part is that you are only building 5 psi of oil when you "have pressure" Ford logic:

Drivers are idiots. Especially those who buy fords... So instead of an actual pressure gauge it will do this: 5 psi or more gauge reads in the middle of "Normal". less than 5 psi gauge reads "L".

So really you have 0 psi and then barely 5 psi... Either way.. Motor sounds in very bad shape.

Manufacturers got tired of owners complaining about their oil pressure going up and down as they drove around town when "real" pressure gages were used, so they installed the "idiot" gage, which does exactly what you say. If you have "enough" pressure, the light stays off, and the needle is always in one of two places: dead center "normal", or bottomed.

 

[raff]

THe relief valve is part of the pump which I noted was replaced. I also flushed twice with new oil. The oil is escaping somewhere and it is not the low end. Oh, and I replaced the sending unit too.

 

[raff]

Also, engine is not in bad shape. Plenty of compression and power. Engine very clean inside for 135K miles. Previous (and only other) owner used synthetic since broken in.

 

[Bobmbx]

THe relief valve is part of the pump which I noted was replaced. I also flushed twice with new oil. The oil is escaping somewhere and it is not the low end. Oh, and I replaced the sending unit too.

I missed that part.

 

[2000StreetRod]

oil pickup tube screen?

Did you check for particles lodged in the oil pickup tube screen? Maybe they are blocking flow into the pump.

 

[rwt101]

Why not buy a regular oil pressure gauge see what you actually have?
Bob T

 

[raff]

There is no blockage to the pump pickup. I may try removing valve covers, reinstalling intake and running to verify that it is not dumping on top somewhere but I have already inspected the left cam and lifters and they are fine.

 

[2000StreetRod]

primary chain guide

. . . My next plan is to go back into the front timing cover and replace the guide and spring. Is that where I'm losing pressure, at the oil port behind the guide? . . .

I assume that you're referring to the primary chain guide and tensioner.

If the guide was broken then it's possible that the oil port normally plugged by the guide could be open.

However, I've never heard of that happening. I suspect there is some other reason for your low oil pressure. Sometimes broken cassette guide fragments get lodged in the cast oil line to the pressure switch. When you replaced the switch did you probe the port for blockage? When you replaced the main bearings were they badly worn or had any of them been spinning? Unfortunately, there are only two places I know of to measure oil pressure: the oil pressure switch port and the oil filter adapter.

 

[raff]

I inspected the guide but did not remove it. The spring was a bit weak and the chain somewhat "sloppy". Is there a seal or O-ring behind that guide? The mains were scored and a bit rough but still holding pressure and functional. The gauge comes up at 1200 RPM now (or just above idle) when previous to replacing pump and mains it would take 1800 RPM. Also, I did blow out the galley when I had the sender off. I do not have to test the oil pressure because if I let it idle (with no pressure) the tensioners go flat in short order and make a clatter. If I keep the RPMs up, and hence the pressure, then it runs great except for the "spark knock" noise from the main chain.

 

[raff]

BTW, StreetRod, your posts on the subject were extremely helpful, thanks!

 

[raff]

Street Rod, I ordered the primary chain, guide, and tensioner. Upon inspection of the guide, I see no seal for that oil port. Is there supposed to be an o-ring there? Anybody know?

 

[2000StreetRod]

no seal

There is no seal or O-ring for the "tit" that plugs the oil port.

 

[raff]

Thanks. Well, I tore back into it, hit the oil hole behind the primary guide with shop air and heard a bunch of air escaping internally. Removed the ladder frame but could not find the source. I did notice excessive clearance (and air escaping) at the rear balance shaft bearing. I then removed the oil pump drive and that is where all the shop air was escaping. Still, the part did not appear to be in bad shape, other than a somewhat worn bushing. I am thinking of removing the balance shaft entirely and plugging the oil supply holes. I see from the forum that I am not the first with the idea but I do not see anyone who has posted after doing this and operating for some time. Anybody out there do this and get lots more life out of an engine??

 

[2000StreetRod]

intermediate shaft?

. . . I did notice excessive clearance (and air escaping) at the rear balance shaft bearing. I then removed the oil pump drive and that is where all the shop air was escaping. Still, the part did not appear to be in bad shape, other than a somewhat worn bushing. I am thinking of removing the balance shaft entirely and plugging the oil supply holes. . .

I'm surprised there was air escaping at the oil pump intermediate shaft receptacle.

I assumed that was a solid shaft and the receptacle would not have a port. Maybe the shaft is hollow and oil travels from the pump thru the shaft to the spiral gears at the jackshaft rear that drives the pump. That seems unlikely to me. Are you sure the air was escaping before you removed the intermediate shaft?

Maybe the oil pump is broken or the spring in the pressure relief valve.

 

[raff]

Street,

I wrote a long response last weekend after working on it but it did not upload for some reason. I decided to replace balance shaft bearings rather than remove the whole thing. I also found the primary tensioner was broken once I removed it. I also removed the oil pump drive and thought it felt worn but the new one that I just received seems the same in terms of play in the shaft. I will finish putting it together tomorrow and expect the chain noise to be gone but I cannot imagine that oil pressure will increase substantially just due to new pump drive and balance shaft bearings (they were not awful). Well, here's hoping. The only thing left if this doesn't work is back in the low end for rod bearings.

 

[abrilsdad]

primary chain guide



I assume that you're referring to the primary chain guide and tensioner.
View attachment 87630
If the guide was broken then it's possible that the oil port normally plugged by the guide could be open.
View attachment 87631
However, I've never heard of that happening. I suspect there is some other reason for your low oil pressure. Sometimes broken cassette guide fragments get lodged in the cast oil line to the pressure switch. When you replaced the switch did you probe the port for blockage? When you replaced the main bearings were they badly worn or had any of them been spinning? Unfortunately, there are only two places I know of to measure oil pressure: the oil pressure switch port and the oil filter adapter.

I have a 92 4.0 push rod with same issue. At cold start no engine noise , like rod knocking or tapping, I do hear what sounds like timing chain going around. I put an oil pressure tester on and it reads maybe 6 lbs and at 2000 rpm it reads maybe 8- 10 lbs. I read somewhere that the timing chain tensioner failing can cause oil blow by and cause low oil pressure. As for pressure relief valve I don't know where it would be or the pressure regulator, if there is one on this engine. I need help too with this issue.