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Discussion Starter #1
Hi all,

I have oil pressure problem with rebuilt s38b38. All bearings are new, cylinders honed/new pistons etc.
I did not built the engine but everything is pretty well documented and engine was never run when i bough it.

I finally get it running but i have serious oil pressure problem.
Pressure will build asap when i start engine, mechanical gauge showing around 3.8 bar at cold idle wich i assume is correct pressure.
Pressure will stay there around 30 sec, then start to fall quite fast, and after ~3 mins it already have come down to 0.8-0.6 bar and i have shut the engine.
At that point oil is not warmed even 50 celsius (oil temp gauge is not moving in cockpit).

It seems like i have serious pressure leak somewhere. All bearings are new so i don't believe problem is there.
Oil pump is old but with new internals. I took the oil pan off and inspected it again but could not see any real problem there, only thing that was little bit suspicious was the big pressure piston wich was not sitting 100% straight.
I took piston from another old pump but it did not seem to have effect.

I have ordered new oil pump from BMW just to be sure (600 euros, ouch), it's not arrived yet, but i really don't believe that is the real problem there.


What other things could cause this kind of leak?
 

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Discussion Starter #2
Btw, anyone here have measured the pressure with mechanical gauge from properly working s38? Would be interesting to know how long it takes oil pressure to settle down to normal readings at idle (around 1 bar if i'm correct)?
 

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Now remember I know nothing about your car, so throwing this in from "left field". Have you by any chance installed an older B34 oil filter housing ? I have done this on my engine conversion S38B36 into my E24 and had exactly this problem. Eventually figured out that the later oil filter housing has a blanked off division which the earlier B34 housing does not. The B34 housing thus effectively short circuits oil from the pump to the sump. Once I plugged the passage I'm registering up to 5 bar. Check my thread here on Bigcoupe; http://bigcoupe.com/phpBB3/viewtopic.php?f=25&t=24940&start=125#p223765
 

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Man sorry to beat a dead horse. but all that money spent on rebuilding engine should have gone all brand new parts to save the headache. i did all new internals from oil pump,water pumps chains tensioners you name it. it has been done. such big risk with these engines make sure you didn't damage the cam gurnals with no oil pressure. Good luck
 

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Discussion Starter #6
Now remember I know nothing about your car, so throwing this in from "left field". Have you by any chance installed an older B34 oil filter housing ? I have done this on my engine conversion S38B36 into my E24 and had exactly this problem. Eventually figured out that the later oil filter housing has a blanked off division which the earlier B34 housing does not. The B34 housing thus effectively short circuits oil from the pump to the sump. Once I plugged the passage I'm registering up to 5 bar. Check my thread here on Bigcoupe; http://bigcoupe.com/phpBB3/viewtopic.php?f=25&t=24940&start=125#p223765
No, "unfortunately" my housing is from s38 but symptoms sounds really similar. :unsure: I'm going to fit another housing just to see If there could be any valve stuck or some other problem.
 

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Discussion Starter #8
Man sorry to beat a dead horse. but all that money spent on rebuilding engine should have gone all brand new parts to save the headache. i did all new internals from oil pump,water pumps chains tensioners you name it. it has been done. such big risk with these engines make sure you didn't damage the cam gurnals with no oil pressure. Good luck
Absolutely everything moving inside is new/renewed. Also oil pump internals. Only oil pump housing/big pressure piston is old (they don't sell that piston separately).
 

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Since you already ordered a new pump, I would try that first. It's possible the old housing is worn. At cold start, the oil viscosity is enough to provide that higher pressure. A lot of oils will quickly shear however and if the clearance is out of spec, it will not provide enough pressure.

Have you applied any increase in rpm while monitoring the pressure? What did the pressure do?

Also, 8-10 psi at idle is not good, but you're not in the damage causing territory unless you drive it/put a load on it or get the oil hot enough to lose even more pressure.

What is the BMW spec range for "hot" oil pressure at idle? Should say in the technical data.
 

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Discussion Starter #10 (Edited)
Since you already ordered a new pump, I would try that first. It's possible the old housing is worn. At cold start, the oil viscosity is enough to provide that higher pressure. A lot of oils will quickly shear however and if the clearance is out of spec, it will not provide enough pressure.

Have you applied any increase in rpm while monitoring the pressure? What did the pressure do?

Also, 8-10 psi at idle is not good, but you're not in the damage causing territory unless you drive it/put a load on it or get the oil hot enough to lose even more pressure.

What is the BMW spec range for "hot" oil pressure at idle? Should say in the technical data.
Sorry for the late answer.
Specs says min 1 bar at hot idle, 3-4 bar at max revs.

Initially, with cold oil pressure will rise sharply with revs, but once oil is warmed a bit, after 30-60 secs pressure will still rise but not enough (around 2bar/3krpm or so).
I also did test with another oil filter housing but there was no difference.

New pump have not arrived yet, but while i googled about the problem i found this: http://www.mye28.com/viewtopic.php?t=105017

While it's not s38, as far as i know B38 supposed to have similar oil spray nozzles for the pistons. Symptoms are quite similar as his, only difference being that i have more pressure at cold oils.

So i'm going to remove oil pan and check if any of nozzles are missing.

I have not found any pics of B38 nozzles but i assume they are similar/ in same place as M30/M106 (as in pic)?

 

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Discussion Starter #11
Alright, oil pan is off and it's unfortunately seems my theory was correct.

It's really hard to get proper view where the nozzles should be, but from what i could see the holes seems to be empty.

933630
933631



Now i truly would appreciate if someone who actually have built S38B38, could confirm that nozze tips should be visible in my pics?
Or if someone knows someone who knows for sure, let me know please :)
 

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Alright, oil pan is off and it's unfortunately seems my theory was correct.

It's really hard to get proper view where the nozzles should be, but from what i could see the holes seems to be empty.

View attachment 933630 View attachment 933631


Now i truly would appreciate if someone who actually have built S38B38, could confirm that nozze tips should be visible in my pics?
Or if someone knows someone who knows for sure, let me know please :)
Problem found! There should definitely be nozzles in there. I even confirmed by looking it up on RealOEM.
 

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Discussion Starter #13
Problem found! There should definitely be nozzles in there. I even confirmed by looking it up on RealOEM.
Yes it seems so. Not really motivated to start to dismantle engine again...damn.
On bright side, it's winter so no driving anyways and nothing is damaged so it could be much worse.
 

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Yes it seems so. Not really motivated to start to dismantle engine again...damn.
On bright side, it's winter so no driving anyways and nothing is damaged so it could be much worse.
Please update the thread when you get a chance to do the work and see if it's fixed.

Good Luck
 

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Discussion Starter #16
Alrighty, got the squirters fitted in couple of months ago, and finally engine back to car and running at last weekend. Can confirm now that all 6 nozzles were missing and that was indeed causing the problem with pressure. So far everything looks good an engine run-in continues. :)
 

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Discussion Starter #18 (Edited)
How were they missing?
I guess the guy who rebuilt the engine simply forgot to put them there. Engine was built years ago with all new internals and some goodies like forged pistons, schrick cams etc, but was never run and it was still sitting on garage when i bought it.
 
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