HELP, no oil pressure...!

[Walt Fricke]

I'm in one of the referenced discussions with my 2.8 liter short stroke with the 930/02 (turbo 3.0, Euro Carrera 1973-7, 6 bolt crankshaft and flywheel.

Since, alas, a piston pulled apart on the dyno, I'll at some time be splitting the case on mine, which will allow me to see if the pump output seal ring is messed up, or a piston squirter got spat out. Or if there is something funny with these cases concerning the oil pressure relief modification. I think they came with this cast in, so the oil pressure setting piston directs excess pressure/oil back to the pump pressure intake, but don't recall how I checked on any of that when assembling the engine. Not sure that would cause this symptom either.

In my case, I used a GT3 pump (huge), while in your case something unrelated to messing around with the engine seems to have happened.

I don't think this is a low oil issue, though checking the dipstick with the oil hot is certainly in order.

I think 10 psi per 1,000 RPM is perhaps more reasonable as a lower limit than 1 bar per 1000. One sees both depending on the source. I got 80-90 psi or so at 8,000 rpm, and the bearings showed no ill effects after 135 race hours. The pressure setting spring has a limit more like 90 psi/6 bar anyway.

But having idle pressure above idle is scary and not right or sustainable.

[bpu699]

Is there any way to pull out an oil return tube and stick in a camera to see if an o-ring popped out/squirter is missing/etc?

It suprises me that there is often no way to daignose these issues short of a complete tear down. If its a newly rebuilt motor, its not the bearings/bushings...

To have oil pressure that maxes out at 2 bar, its should be something pretty obvious...no?

Could it have been assembled with the wrong pressure relief cylinders?

Bo

[E Sully]

The interesting thing with this engine is that the bottom end was not touched according to jsveb.
The oil pump and seals have not been disturbed. 12 quarts is plenty to start with. Have you dropped the sump plate to check the oil pick up tube, maybe remove the large oil hose from the engine to the tank to check for blockage?

[Walt Fricke]

Bo

If you had a surgical grade scope, you just might be able to check something like this. I can tell you that with the common borescopes, both with and without a 90 degree mirror on the end, I don't think you can. I've spent some time with an engine on an engine stand trying to see what you can view running the scope down the return tubes, and it is pretty limited. If you could maneuver things like the surgeons seem to be able to do, you could get in much deeper.

One way to have oil pressure problems is to wear through the Babbit on the bearings. This can as easily be coincidental to the work done as not. I once trailered the better part of 1,000 miles to TWS to race. On the test day, my wife drove first, and came in after a slow first lap. The big red light came on, and wouldn't go off, she said. Well, that was my low oil pressure light. I spent a day trying to blame this on faulty senders, and issues with the various oil pressure setting mechanisms. No joy - just wouldn't make pressure as RPM rose.

Back home, tore down the engine. Rod bearings were shot. Big red light (and a sender which closed contacts at 30 psi rather than the stock 4 psi) saved a blowup. The crank was salvageable, rods were fine, no other damage.

I think you are looking at doing a teardown. The top end work may have had zero to do with the oil pressure problem. Or, maybe, the first startup after a long time without running may have been on a slightly thinner oil film than would have been the case had the engine run regularly, and that was just enough to wipe a bearing or several. Which would eventually have happened anyway in a short period of running. So maybe this saved you from it happening when driving around, and more so from continuing to drive just to get home.

[Walt Fricke]

Oh - and even if you could see something useful with a scope, you couldn't fix it without a teardown.

Still worth pulling the sump plate (if motor is old enough to have one) to see what can be seen. Maybe you will see something which you might be able to fix (loose suction tube, but that doesn't seem to be the issue). You will have to drain the oil anyway, so why not start. You could collect some of it and send it off for oil analysis. That ought to tell you if your bearings are shot, I think.

[Lapkritis]

Could cut a return tube out to inspect and replace with an accordion type the host sells if necessary. That would gain you a view into the side of the engine at a cost of the replacement expandable tube(s).

[jsveb]

I am reading all the excellent suggestions - really appreciate it.

I have put the car on jack stands, and am just hoping to find time to start working on it.

The first I will do is check the press relief, then remove sump plate, and then the oil return tubes. I happen to have the sweet alu collapse able tubes from our host. I was going to replace oil anyways because of the "rebuild debris" that might be in there.

Maybe a boroscope will become part of the tool inventory depending on future findings.

I'll report back as soon as progress has been made.

[jsveb]

Last night I went out and gave the newly acquired tool a go.

I could comply not keep it engaged in the groove. So I went to drastic measures, and used a hyd jack to put pressure on the ratchet. It wasn't much, but certainly more than I could push from under the car.
Well, the flat iron just twisted and bent, under a quite significant pull on the ratchet. -The oil press relief plug did not budge.



I will try and fab some more sturdy steel for the insert today, couldn't yesterday eve, as the kids were sleeping.
I must say, I am not too optimistic right now.

Btw, it has been soaking in Gibbs for about five days now

[fred cook]

I just used the one that I made and it worked as intended. Perhaps I used either a thicker piece of steel (1/8") or a stronger grade of steel. On the other hand, I had the valve out of my engine during the rebuild so it was merely tightened against the block and seal, not frozen in place after many years! When I was disassembling my engine, I used a small pipe wrench to loosen both the bottom and side valve plugs. Of course, the heat exchangers were not on the engine which made room to use the pipe wrench. If your second insert does not work, send me your mailing address and I will send you the one that I made to try on your engine.

Originally Posted by jsveb

Last night I went out and gave the newly acquired tool a go.

I could comply not keep it engaged in the groove. So I went to drastic measures, and used a hyd jack to put pressure on the ratchet. It wasn't much, but certainly more than I could push from under the car.
Well, the flat iron just twisted and bent, under a quite significant pull on the ratchet. -The oil press relief plug did not budge.



I will try and fab some more sturdy steel for the insert today, couldn't yesterday eve, as the kids were sleeping.
I must say, I am not too optimistic right now.

Btw, it has been soaking in Gibbs for about five days now

[fred cook]

Ok, I'm not going to hijack this thread, but my newly rebuilt engine is doing the exact same thing. From cold, starts with good pressure but within about 1-2 minutes of idle time, the idle pressure drops to about 1/2 bar and at 3k rpms will only pull about 2 bars of pressure. I have replaced the gauge sender and opened up the oil pressure relief valve to make certain that there is nothing stuck in the bore and that the valve head will move freely in the bore. I have not checked the oil pressure safety valve on the bottom side of the block. I'll take my "issues" to a new thread.

Thks,

Originally Posted by HawgRyder

Fred...the scavenge side of the pump is not monitored...it just sends oil back to the tank.
Even if the sump were full of oil...I don't think it would affect the oil pressure monitored by the guage.
If the pressure problem were the other way around (starts low...goes high) I would say the tank starts out low or empty...accounting for the time lag in pressure change.
But starting high and going low sounds like a relief valve opening too soon...or one being stuck open or partially open.
If the thermostat were at fault...would the rush of oil to the front account for the change? (not likely).
The relief valve (high pressure one) sounds more like the culprit...opening too soon or stuck.
Jesper...the way I normally grab those relief pistons is with a tool that looks like one of the long reach grabbers (expanding wire arms on one end...push button to activate on the other) except mine is one with the end arms that expand outwards with the "teeth" pointing out when the button is pushed.
The idea being...grab the relief piston from the inside surface...so that the bore is not damaged.
John Walker and the guys probably have a special tool for the job...LOL....but I'm cheap!
Bob

[E Sully]

There was another thread with startup pressure problems after a rebuild due to a shop towel left in the bottom outlet of the oil tank. Poor supply, poor pressure. First thing I would look at is to make sure oil was flowing freely to the pump. It could explain the rapid pressure drop, There is enough oil collected in the supply line when started to show pressure, but supply is not enough to maintain feed to pressure side.
Does the level show properly when warm at idle with around 12 quarts? A stable level would indicate the sump is pulling oil and some is flowing to the pressure side of the pump. A low level would indicate a problem on the low pressure side, and a high level would indicate something wrong into the high pressure side.
These are some specs I found. Interesting how the pressure has gone down through the years, and the temperature spec on the 81 and up is higher.

[jsveb]

Originally Posted by fred cook

I just used the one that I made and it worked as intended. Perhaps I used either a thicker piece of steel (1/8") or a stronger grade of steel. On the other hand, I had the valve out of my engine during the rebuild so it was merely tightened against the block and seal, not frozen in place after many years! When I was disassembling my engine, I used a small pipe wrench to loosen both the bottom and side valve plugs. Of course, the heat exchangers were not on the engine which made room to use the pipe wrench. If your second insert does not work, send me your mailing address and I will send you the one that I made to try on your engine.

Thanks for the offer it is very generous, but I think I know what will happen to your tool then, can't have that.

Today, I made the tool, as suggested, using 1/8" steel. Guess what, after not being able to get the plug to budge, I grabbed it really good. It simply twisted, and is now useless.
I was real proud of how I made it fit before this, it had he crescent shape and was a tight fit to seat, it was perfect. But, I guess that plug hasn't been out for a while...

I then decided to go ahead and drop the oil. It looked brand new and clean.

I found no debris on the magnetic plugs everything looked good, as far as I could see.

I took some pictures:






I was able to move this shaft axial between the two locking rings, is that normal?


Engine mounted oil cooler pipe, looks ok, doesn't it?

[jsveb]

There was no signs of anything blocking the oil tank supply lines. I had a new rubber S hose, I installed it.

Some more shots of the engine interior:

[jsveb]

Fred, I just read your thread. I am sorry to hear you have issues as well. Best of luck and post all you want. We most solve this, for both of us.

[HawgRyder]

The spines on the oil pump drive shaft are fairly long....some end to end movement is OK.
I would be more worried if there were no movement...because heating will expand things and perhaps bind the pump.
Bob

[jsveb]

Thanks hawgRyder, just checking what I can.

[fred cook]

Jesper,

When your engine work was done, was the internal oil thermostat replaced? The reason for my asking is that my engine is having the same oil pressure problem as yours, and, I did not replace the oil thermostat in my engine. I have gone thru everything else, even pulled the sump plate to make certain that it was assembled correctly (it was). Since you only had a top end rebuild done, it would seem logical that the problem is not in the block but could be in the heads or one of the peripheral parts or subsystems. Even though the block was split on my engine, I haven't been able to find any pieces of seals, etc. that would point to a reason for the problem.

[jsveb]

Fred, I just read your latest post in your thread with great interest.

I don't believe the thermostat was changed, or removed. Maybe Bruce can remember that?

Crazy thought: since I have my sump plate removed as well, can I blow compressed air through the pressure canals to make sure there is a free passage to the pump? I am talking maybe 2-3 bar. This way I should be able to hear hissing in the case... Or what?

[Flat6pac]

Jesper, I probably changed the O ring on the thermostat. You would be able to tell because the last couple years the O rings have been leaking from new so I install the thermostat with 574 Loctite (orange sealant) at and above the O ring for a better seal.
The thermostat can only go in one way.
For reference, I did the bottom row of studs and a fresh topend, never removing the P&Cs.
Some readers think the case was split, it wasnt.

Bruce

[jsveb]

I will say it again:

It was just a top end rebuild, the case was never split!

Bruce, do you think a malfunctioning thermostat could affect this? Or rather what would you be looking at in your investigation?