txhokie4life

Searched -- didn't find my exact situation.

Bought a 86 951 last year -- fought blow by and oil pressure issues.

typically had 3 bar at idle, could rev to 3.5bar
but when warm would drop to 2bar.

Eventually lost pressure on track that led to a #2 rod bearing failure.

Complete rebuild -- including resleeving the old iron sleeves,
new bearings, rod & main, baffle, cross drilled crank, complete valve
job -- the works. Replaced the oil pump as well (with expected good used pump)

Runs great -- however I'm still at 3 bar at idle, 2 bar when warm.
Every now and then I think I see it bounce 1/2 bar -- think it did it before rebuild as well. This would only be prior to being warm.

Just happens the sender had a post break off during rebuild -- so I had to put in a used sender (from an early 944). Possible both before rebuild and after rebuild senders were bad -- but unlikely -- and the values are very similar.

Checked crank bolt -- it's at least 150# (max my torque wrench would goto)

Pulled instrument cluster -- cleaned connections -- no change in values.

redid OPCV -- it looks ok.

We also pulled a cam plug and observed oil in cam housing -- but not a overly large amount -- seemed reasonable (but not like I'd know for sure)

Switched from 10W40 to 6qts 20w/50 + 1 60W racing oil,
no change in pressures.

We measured the voltage across the sender
got the following
8.7v idle cold (1100rpm)
revved to 4k rpm -- 8.4-8.2 v (semi-cold) maybe 4 bar.
9.5v 2 bar warm.

The room temp was about 95-100 degrees.

Couple Questions.
What are normal sender voltages?

about 20-30 min after idle testing -- we measured oil cooler with infrared.
(I have an RX7 style cooler) . It was basically room temp 103f?
oil pan was 125ish at that point, water hose was still 140F

wondering is OPRV is partially open -- dumping pressure to sump
with out circulating and therefore shunting some of the oil pressure?
Also possibly preventing from going to cooler?

pulling my hair out as I've dumped a good chunk of change on the rebuild
and I'm not tracking until I get a solid OP.

My chumpcar 86 944 N/A is 5+bar and never less than 4 even after 7 hours of racing (unless we hole the block :-)

mike

fortysixandtwo

Check Clarks Garage for testing the oil pressure gauge system. The anticipated ohms to pressure values are listed there as well as trouble shooting steps.

If you're unsure if the gauge is reporting the correct pressure, the best way to verify is to install a separate mechanical gauge. You can pick up a very cheap one strictly for temporary installation, or get a better setup and use as a second reference gauge since you'll be tracking the car.

The opvr could be stuck partially open. You would have to remove it and check for any signs of debris that could be causing it to bind. Possibly it's just worn, or it could have collected some left over rod bearing that may have not come out while flushing the oil system.

Having the oil cooler not having circulation, at idle, would be normal. The opvr will dump oil back to the pan to regulate oil pressure (almost like the waste gate bypasses the turbo), but thats the end of its function. The oil cooler uses an oil temperature thermostat to either direct oil to the cooler, or bypass it. The thermostat is located in the oil filter casting, below that giant aluminum cap with a big hex socket.

txhokie4life

Smoking Gun.

Left side is from my 951
the right side from my 88 924S Chumpcar.
Left one is seized -- probably from internal corrosion - I ready the 86 one piece was replaced in 87
with a corrosion resistance one

Hate to have lost an engine trying to sort this out -- but
I was chasing down several issues, including blow by that was causing
back pressure in my oil system and causing oil loss.

Now I just need to figure out which one is the right one to get and
find a "new" one piece at a reasonable price.

Mike

Van

What part is that - I don't recognize it? It doesn't look like any of the 1-piece or 3-piece OPRVs I've seen... and it's not the oil cooler bypass valve...

refresh951

+1 I do not recognize this either.

txhokie4life

My mech buddy pulled it out (and probably apart) and took the picture.

Its the business end of the OPRV -- left one is 86 one piece, right one is an 88 one piece (I think)

Mike

Van

OK, I've never taken a 1-piece OPRV apart. It must be the plunger from inside. There should be a spring, too. I think the small cylindrical pin in your picture is just a guide for the spring. I wouldn't think that the pin would be the problem...

But put a new one in and let us know the result!

txhokie4life

Until I can find one for a reasonable price --
anyone know if a 944 3 piece can be used as a substitute?

Even if for no other reason than testing?

Mike

Van

I know the answer to that - yes, the early 3-piece can be substituted for the early 1-piece.

I think OPRVs are pretty pricy, so there may not be one "for a reasonable price"...

MarkRobinson

Update: Hokie has his oil pressure now with the proper OPRV. Yay! Now hopefully the oil thermostat will open as it should...cause it didnt' Sunday even after 20m of 100d idling.

txhokie4life

Actually -- I have put in a 3 piece as a test.

I have 5+ bar when cold.

30min idle -- dropped to 2bar
4bar at 2K, punch to 3k I get 5bar
then drop back to 4bar at 3k

think 3 piece is not 1005 working properly -- will be on the search
for an old style 1 piece retrofit for (well) under $420.

But yet -- it looks like the source of the issue is the OPRV.

Mike

txhokie4life

Does a late Oil Cooler Housing fit on an 86 turbo?

thanks,

Mike