timf

I've posted this over on the other porsche forum - but appreciate comments from experts here before I start.

Problem - when I leave my 2003 996 turbo parked for more than a few days when I come to restart it there's a nasty clattering until the oil pressure comes up and the warning light goes out.

It didn't use to do this.

I'm getting ready to do an oil change and while I'm at it I'm thinking of changing the non return valve part # 996-207-012-74 which attaches to the bottom of the oil tank. I may also opt to refill with 5-50W oil.

Does anyone know of any other causes of this problem or how to diagnose ?

Thanks Tim

DaveK

I know this doesn't answer your question - but how many days is "more than a few days"? I've never noticed that my oil pressure takes time to come up / the light takes time to go out? All my lights extinguish pretty much the instant I start my car, even if I haven't used it for 3 or 4 days?

timf

Hi Dave,

if I leave it more than about 72 hours it seems more prone to making this noise.
If I leave it for 7 days it's almost guaranteed to make the noise.

Seems like the oil is draining away from places it's needed and that it could be check valve related.

But as mine is a 2003 it should have the improved part installed - of course it could have failed all the same so I thinking for $130 for the part I should just go and change it anyway.

In the meantime it gives me an excuse to drive my turbo every other day :-)

jpflip

Hello Tim! I got the exact same problem but now it is worst. Now after 24 hours I got this clacking on start up. If you look at the pressure gauge you will see as soon the pressure rise the clacking stop. My opinion on that is this check valve at the bottom of the tank that is not closing properly and the oil from the tank end up in the crankcase. So, since the pressure pump is taking his oil from the reservoir and there is no more oil in the reservoir. It has to wait for the scavenge pump to redirect the crankcase oil to the reservoir. That is the delay. There is a TSB for that and they replace that check valve. If it got a blue dot it is and updated one. But I do have an updated one and I am wondering if the seat of this valve can get dirty. I did a check of that valve last year and it is a simple ball that sit in the bottom of that valve.... I am working on my car right now and may be if I got time I will remove the oil from the tank and take a look at this check valve.

timf

Hi jp,
Thanks for posting the above again, your symptoms are identical to mine - I'm beginning to think even the later check valve can have a problem. It'll be interesting to hear what you what discover - assuming you have time. Fortunately seems like an easy part to change and just involves me performing an oil change a little sooner than planned.

Edit - I wonder if this possible check valve problem could also explain the increased number of 'smokey start ups' I've been getting recently ?

jpflip

I think so. Because this excess of oil,in the crankcase, can found his way through the piston rings towards the combustion chamber. Typical on a boxter engine but may be worst in our case since 8 liters of oil is searching for a place to go I am just expressing an opinion here....

jpflip

Tim, look at the second step of the TSB. Loosen oil tank mount bolts.... They are really difficult to reach. I am getting prepare to do it but I don't have a good set-up. No lift.....

nick49

What kind of clutch is in that? looks like a multiplate motorcycle design.

timf

Jp. a cpuple of things - it looks as though the check valve is attached to the bottom of the oil tank and would be fairy easy to access and change. I wonder if it's really required to loosen the oil tank bolts as per step two ? Maybe you're going to find out soon ?

One other thing - what does your oil pressure gauge read with the ignition switched on, but without actually starting the engine ? Obviously the oil pressure light will be on.

I was expecting it to read zero but on close inspection it reads about 1.2 - residual pressure in the system maybe. If that's the case I wonder if the clatter is still there because the residual oil / pressure gets pumped out before the oil tank is replenished ?

jpflip

I got it out Tim and it is not so bad because of flexible tube in the bottom. But I have found a reservoir mount bolt in the bottom, took it out (13mm bolts, two wrenches) and attach the tank away from the valve . I had about 1/4 inch more play. After I attach the flexible pipe to an handle and took it away from the valve. And finally took the valve out of the crankcase which was really tight. Needed to pry it while turning it from the crankcase.....

I did not found anything wrong with the valve or the valve seat except the o-ring on it was a bit elongated. So I am now wondering if the spring on that valve is a bit weak or if the new updated valve have now an improve spring with higher force needed to open it

To my big surprise I found out there was 5 liter of oil in the reservoir (the car was last started 5 days ago). Enough for the oil pump I guess. My second discovery was my valve seems to be an old type with a number on the body that I cannot found anywhere 996-207-112-2R ??? Anyway I order from Pelican the last updated valve part# 996-207-012-74 two o-rings crankcase side part# 999-707-316-40 and one o-ring reservoir side 999-707-364-41 (total $130.50)

Hope this help. I will let you know when I got everything together.... Anxious to see the updated valve and measure the spring tension....


About your question of oil pressure, mine was always below zero. And for the second part of your question about this residual pressure, sorry I got no clue...

If, after replacing everything, it is a fix I will do a DIY on Rennttech...

timf

As always Jp - excellent work and photo's. I'm sure I'll be making good use of your experience when I change my check valve in the not too distant future.

Macster

Can't imagine any oil pressure remaining any length of time after engine shut off. The only thing that keeps the oil "trapped" and under any pressure is the oil pump gear teeth which of course have some clearance at their ends and the close fits at the other end of the pressurized oil passages. These include main bearings, rod bearings, camshaft bearings, chain tensioners, and oil passages that feed the hollow cams and the lifter bores.

While all of these end at close fitting parts, except the hollow cams which have an oil hole drilled in the base of their lobes, they can not hold much pressure.

So if the gage reads any pressure the gage or the sender is flaky/bad.

Sincerely,

Macster.

timf

Hi Macster

I was also thinking it might the oil pressure sender or gauge causing the residual reading when cold. I tend to agree that I'd be surprised if it was for real.

Just thought I'd mention it in case anyone else had observed the same reading.

Tim

jpflip

Just an update for the replacement of that valve. Got the parts las week and found out it is exactly like the one removed. The valve release at the same pressure which is about 7.7 pounds. Four days later , start the car and got the same growling on startup for about 2 to 4 seconds or until the oil pressure build up.... Sad because I spend $130.00 for nothing really ;-( Next step, oil viscosity....

fdorn

jp, curious what oil you are running. I am using 0-40 but am switching to 5-50 (after the winter).

I have a read a lot about 0-40 vs 5-50, but not enough in plain english to really understand what to use and when. I think I remember that you should use 0-40 in the winter, but 5-50 in spring, summer and fall, but don't remember the reasons.

tia,
fd