Relief valve in the head

[944 boy]

I rebuilt the motor in my car last summer and I have not been happy with the oil pressure ever since. I noticed that the parts diagram has two valve like parts listed to go in the head. I pulled the cam towere off the old motor and took a picture of the valve that is installed. I gave the entire head assembly to the motor shop to get checked and cleaned. They gave me back all the old valves and parts that were removed. One dowel pin was taken out and had to be replaced. They also bead blasted the head. I however do not remember anything specific about this particular valve assembly. Does anyone know the symptoms if this part was bad or missing? Also is there a different part for N/A's vs. Turbos? I have gone through every external cause for the strange oil pressure I am getting and I am down to replacing and re-sealing the oil pump. If I can help it, I want to make sure that is the last resort.





The symptoms:
4.5-5 bar at cold idle
2 bar hot idle
4 bar 5K rpm luke warm
3.5 bar cruising long distance
3 bar or less @ 5k -racing (when I call it quits and pull in)

also when I hit the gas driving at one speed the oil pressure drops, when I let off (coasting down hill at the same speed and RPM) the oil pressure goes up .5-1 bar. This has been confirmed with a mechanical gauge.

Fuel pressure checks out OK. 30psi at idle and 15psi after 20 minnutes. Closer to 40 with the vac. line pulled. Checks out with the specs from Haynes. There was a theory that it was running way lean and heating up the oil far beyond the water temp. (H2O temp is nearly always perfect) I still havent checked out the pump volume, but its not as likely at this point.



Any ideas other than another full rebuild are welcome. I want to find out what I did so the same mistake is not repeated on the next motor.

Thanks!
-Greg

P.S. if anyone has a DME for an 88 with the last digits ending in .05 I am interested. Even if it needs resoldering or has a chip. We bought one that ended up being an 87 DME (.04)

[Icey1174]

Do you still have the 87 DME? How much do you want for it? I don't have an extra one but I have heard of people keeping spares.

I would be worried about the 3 BAR oil pressure at 5K too. Fuel pressure sounds good. I didn't know it droped that low with the vac lines on. I thought it should stay around 44 PSI +/- maybe 5 PSI on cruze. I have a FPG mounted to my fuel rail. With my stock injectors and stock FPR I was getting 40 PSI. I put in 36# injectors and an AFPR and I bumped it down to 20 PSI. But if the book says that's normal then I'm sure it is.

I just did my cam gasket and I'm not in a big hurry to go pull it off to see what mine looks like. I wish the PET had the other side view of the head.

How's the oil level? When my n/a used to leak oil I would notice my oil pressure get lower as I lost oil. It was still in the good section of the dip stick but a little on the low side. If I filled it to the upper limit I got my normal oil pressure back.

This is from the FAQ:
"For highly modified vehicles pulling very high cornering G’s, it ispossible that the oil will slosh away from the pickup causing theengine to starve for oil (read: big engine damage). The 89 944 Turbo and S2 have an additional pan baffle to help avoid this problem.This part will fit other 944’s. The Oil Pan Baffle part number is 944.107.389.03 and costs approximately $65.97. This may not fix the problem entirely, but it may help."

http://www.connact.com/~kgross/FAQ/944faq08.html

FYI: I don't know where the "big engine damage" section is. I looked for it, but I can't find it.

[944 boy]

I has since developed a few minor leaks, but I can go 3K miles without adding any oil. That kind of bugs me too. I'm not used to a 944 that doesn't burn oil. And this happens whether I am in the strait or in the corner. The 88' has the better baffle than most to begin with. So hopefully I haven't cooked the bearings yet, but we will see. I do still have the 87 DME, I'll pm you a price when I figure out what I want for it later today.

[Icey1174]

ok

[toolboy62]

OP dropping when nailing the gas sounds like loose rod or main bearings to me. All cars do this to some extent but 1 bar (14 PSI) sounds excessive. My old Studebaker would only drop 2-3 PSI (had a good mechanical gauge on that) and my 944 even with 130K miles will only drop maybe .5 bar with the engine fully hot.

I suppose a sticky OPRV might hamper the engine's ability to compensate, if say it were slightly open during steady state cruising. Did you align it with "the tool" when you reassembled?

nate

[Icey1174]

I have heard of either no oil pressure or so much pressure that it blows the oil filer off the car if it's not aligned correctly. I don't know that it could be that close. Maybe it needs to be cleaned up or replaced. Most oil pressure problems point to that on these cars. This one may be a little different with the possibility of this other part missing in the head.

Maybe Sid wil jump on here and have some input. He seems to know these engines real well and he knows his fair share about racing.

[924Sman]

Was the oil cooler changed? If so was an alignment tool appropriate to the year used? No....then you have to re align the OPRV and seals. 5 bar at start is ok and should be around 3 to 4 normal running. You are not that far off. But if you are blowing the oil filter off so to speak you have an OPRV issue.

Dal

[944 boy]

I should have mentioned the oil cooler things that I have done. I do have the correct tool, and I have replaced all of the seals and changed between two OPRVs, one of which I know is good. The bearings were all new when i rebuilt the motor and all tolerences came out within spec. The problem has exsisted since i first started the motor. The pressure is OK for street driving which is why i have taken a year to trace it down, but for racing it is far below par. Most 944 racers say that it should never drop below 3 at idle and never below 4-4.5 when your on the gas. It is critical when you spend most of your time at 5-6K rpms.

Other tidbits: The oil pan is an '88 pan and has the correct dipstick
Crank was checked, magnefluxed and crossdrilled
Installed a crank scraper and measured corect tolerences at every point.
Always used german filters and synthetic 15-50. 5 oil changes later and there has been very little on the magnetic drain plug.
Re-used the oil pump and drive gear from the motor (unknown state, next to get replaced)
Upon startup it takes a second or two to build pressure and just spinning the motor with the started does not build much pressure at all. eg compression check

Some thoughts are that the oil pump is sucking air and cavitating, sound feasable?

[924Sman]

Issue with the oil pump drive gear is a groove gets worn into the outer surface where the oil seal sits, then leak. If the gear is not in totally it may be spinning the pump drive but not fully toothed. The drive gear has a slight taper in the teeth and may be just catching. I find this to be slim though as the crank bolt is at 150 lbs but there could be a small void at torque where the gear is still not fully engaged..?

On the cheap change to dyno 50w and see if it has any bearing. Oil level when this occurs?...Also did you use the clear plastic shims on the cooler?

Dal

[blown 944]

I would look at the tension of the crank bolt as it is what drives the pump and may be slipping alowing the gear to slip (against the lower belt pully) at high revs. Consider that at teh higher rpms there is more stress and pressure thatn may cause the non keyed pump drive to slip. apoor design i you ask me.

Looking at its behavior this is my main suspect ^^

[944 boy]

I did check the bolt and yeah... its at 150 at least. And yes the oil cooler is shimmed, but with the factory metal shims. ;-) I have wracked the brains of the best and the brightest, i might as well pull the cam tower and make sure a relief valve is there, if it is, then oil pump time. If not that, new motor.

-Greg

[924Sman]

Any clue on the condition of the pick up tube? iirc my shims were clear Mylar but I suffer from "short term memory loss"! I would ask George B/944ecology on the valve and how it plays a role before removal, then if he provides info that leads to that valve then remove it.

Dal

[jwade944]

The oil coolers in these cars are pretty weak and my race car has never been able to maintain decent oil temperatures or high oil pressure when racing in hot weather. You may want to add an external oil cooler if you are tracking the car. You may also want to make sure that the radiator and other cooling components are working properly.

[944 boy]

The radiator and H2O pump are good, I have been running strait water and water wetter. I am trying to source an oil cooler. My reference mark is my dads car that when racing in the same conditions can maintain oil pressure and temperatures. His motor is dead stock and does not have an external cooler. I will work on calling George and see what he has to say. Also the pickup should be in good condition, but possibly a seal was not seated correctly. I am trying to avoid a compleate tear down, but its looking more and more imminent.

[924Sman]

I use a sandwich plate from MOCAL...SPD1T iirc....It has a thermostat at 180. Homemade steel oil lines with AN fittings to a oil cooler radiator from a early 911. Mounted the rad up near the lower right fender closest to the center as possible.

Dal