jonnybgood

The Pressure Reducing Valve resides in the cylinder head and apparently is supposed to provide a reduced pressure to the cam bearings and lifters. Last year I installed a rebuilt head. The head had been done by a reputable SoCal firm. Driving the car the past year the lifters have been noisy and a couple times got really loud. When I restarted the car last year after the head install the lifters took a very long time to pump up, longer than other 944s with oil depleted lifters.

Tonight I removed the Pressure Reducing Valve and the o'rings were hard as plastic and I doubt they have been sealing properly. The rebuild did not touch this part for sure. So I guess my question is this, If the o'rings were not sealing or the valve defective then why were the lifters making noise? It seems to me that with greater pressure they would not be making any noise. Or does failure of this part result in lower head oil pressure?

Anyway, a new part is on order and I will find out when I replace it but I wonder if anyone here can shed some light on this overlooked part. There is only a single paragraph on this part in the FSM and I could not find it on any of the S model head parts diagrams.

Oops, it is actually called the pressure relief valve, P/N 944 107 139 00

Thanks

xsboost90

i guess you have the one piece relief valve? i doubt it would stick closed, and if it stuck open it would allow for oil to drain out of the head overnight and it would clatter when you started it. Doubt the o-rings would do it though.

tkacki

The oil preassure gauge on dash reads the preasure after OPRV, so if the readings were fine, OPRV is not cause of the lifer noise. I my case (3.0 S2), the new dry lifters needed about 4h of driving to be quiet completly, then zero noise now hot or cold, even during cold start after two weeks without driving.

Replace Your lifters.

jonnybgood

Thanks for your both of your replies but this is not the OPRV. This pressure relief valve is located in the cylinder head. If you are standing on the passenger side of the car, looking down at the engine, this valve is located beneath the cam cover in the lower left corner. I am sure this valve is in all the 16v engines and the 2.7l 8v engines, not sure about 2.5l 8v.

thacki, the lifters were all checked and four were replaced.

xsboost90

all of them have it- but older motors have a three piece design instead of the one piece design. If you have a screw(alan) on the side of the head that holds it in, then it is the one piece design. The three piece you have to drill or press it out. If you are pulling it out easily then it must be the one piece- which is real expensive- you may want to pull it out and see if its stuck open- can you blow through it both directions?

tkacki

Wrong. "This valve is located beneath the cam cover" - You describe oil preasure CHECK VALVE !!! OPRV is near lower balance shaft cover.

jonnybgood

This is helpful, yes it is the one piece with the set screw. I think the person who installed it tightend the set screw too much and may have caused this valve to jam. The FSM says to tighten until contact is made and then back off a 1/4 turn.
I am going to try getting new o'rings for this one and see if that helps. I will also try your test.
Locally I found $175.00, online $260!

Thacki, check valve, relief valve, reducing valve, whatever my point was it was NOT the OPRV. I thought that was what Dan was talking about when he was asking about a one piece valve.

krahmlow

Just to be a PITA, if it's 944 107 139 00, the parts catalog calls it a "pressure relief valve."

Please be sure to post your results when you get it back in and adjusted. I'm curious to see what effect it has on your problem. I didn't touch mine when I did a valve job last winter, and my machinist didn't touch it. I think we both assumed it was pressed in. Now I wish I'd taken a closer look.... I don't remember seeing an adjustment screw, though.

Otherwise, and I'm assuming you're talking about a 16V engine, here, looking at your signature, have you got the pegs blocking the oil holes on the empty cam saddles on the back end of the head (the original parts look like plastic caps with pegs coming off them)? If they've gone missing somewhere along the line, you could possibly have lowered oil pressure in the cylinder head area. Just a thought.

Kurt
'87 944S

Jay W

Ok I just went through this. I had a timing belt failure on my 944S so I took off the head and had it rebuilt. Put it back on and went to start it. Got practically NO oil to the top side of the head. Let it run for 15 minutes and the lifters were still making alot of noise and barely any oil on top. I thought this was normal amounts of oil getting to the top and read other posts about the 16 valve motors taking up to 30 minutes to quiet the lifters after a rebuild so I put the valve cover on. Ran it at idle several different times up to about 15 more minutes and still the noise. Pulled off the valve cover and discovered that valve under there. It is designed to shut on engine shut off so oil stays up on the top side for the next restart. Pulled the valve out and it had the same brittle o-rings you describe. Changed those out, connected the valve to my air compressor and made sure the valve opened under pressure. It did have bits of metal stuck in it from the machine work. Turned the engine over a few times with the valve out to make sure oil was getting up to the valve and oil shot all over the underside of the hood and the garage door next to me. So I knew at that point it was the valve sticking SHUT, stopping the oil flow to the top of the head. Put the cleaned up valve back in, started the car and immediately oil was GUSHING out where it should be by the lifters etc and within seconds the lifters quieted down. I posted about this and advised other 16 valve owners to check their valve and replace the seals because I know that I had premature wear on my timing chain pad and tops of the lifters because of oil starvation on top for many miles. The wear was all prior to the timing belt going bad. Good luck and I hope other 16 valve owners are helped by my experience.

jonnybgood

Jay W
I read your post some time ago. That was what got me thinking about this so thanks you did me a favor. I searched for the post but could not find it. My lifters have not been loud all this time but they have been noisier than they should be.
I think my problem was the PO tightend the set screw too much and deformed the body. The valve is not operating smoothly, it sticks up and down. I have cleaned it with alcohol and LPS and it has freed up a bit but I am going to replace it.
I also got new O'Rings for it. They are not listed in the PET. The correct sizes and anybody reading this later can order them with the Parker o'ring numbers: 2-013 and 2-014. Get them in Viton and you should be good.
Finally, Volume 1A-Engine of the FSM on page 17-102 calls it the "Pressure Reducing Valve". Vol 1A is for the 16v engines. PET in illustration 103-4 calls it "Pressure Relief Valve" (944 107 139 00). So there we go, it is not OPRV though!
To solve any further debate here is a picture:Sorry, Rennlist is not letting me log on!

jonnybgood

The black disks are intact with the bracket off to the side with a bolt in it. I think that is what you are menioning, Yeah they are there.

tkacki

OK. The part is 944 107 139 00. This part is not OPRV. We all are correct. IMHO, the manual/PET calls it in strange manner. Jay W perfectly described the purpose of this valve - one way valve preventing the oil to draw back from top of engine after engine is shut off. IMHO the one way flow valve is called "check valve". IMHO this valve is not reducing the preasure....

jonnybgood

Quite Lifters! Yeah Baby!! I got it all back together completing new water pump, balance belt, rollers, timing belt, rollers, ISV and cleaning the valve in the head. The lifters were still clicking at start up but after 10 minutes of driving they were silent the way they should be. That is great, thanks Jay!
It is an interesting simple valve that does keep pressure constant in the head despite changing pressure from the pump. As the oil pressure increases due to speed of the engine the oil presses the plunger up farther. The plunger at the bottom closes off the inlet holes so less volume/pressure gets up to the head. When RPMs go down the plunger comes down allowing more oil/pressure to the head, very clever. Then when the engine stops it serves as a check valve to keep the oil in the head.

krahmlow

Jon, where did you get the o-rings?

Jay W

Well I am glad that you got it together and working fine! It always feels good to be able to share my experiences with my cars and help others get their cars together faster. Thats what this forum is all about. I am currently tracking down an oil leak in my car near the oil cooler and this forum is where I am doing all the research to learn how to fix it. I am happy you didnt do like I did and run the engine with hardly any oil getting to the topside. I have since put about 3,000 miles on the engine so apparently I didnt do any permanent damage to it.