Waldteufel

My 97 daily driver C4S went its first 128k miles without more than a trace of oil transfer noise at start-up, but over the past 500 miles it has developed such a gurgling commotion that it sounds like a dishwasher on drain cycle. Of course, it quiets down after about 2 minutes, but it just doesn't sound or feel right at start-up. Logically, the problem seems like it should be that the thermostat that extends the circuit out to the oil cooler (at about 181 degrees F) is stuck in the open position. This would then cause the cold oil to immediately circulate out to the cooler at start-up.

First of all, does this sound to be the likely cause, or at least plausible? Secondly, might this diminish cold-start oil delivery to the engine? Thirdly, would this thermostat be a pain to change, or expensive work to have done?

I'm soon to take the car into the shop to have the heads pulled to install new valve guides and have the SAI ports cleaned. I'm also having Fabspeed 200 cell cats/x-pipe installed. I figure that with the factory motorsound package, the addition of the 200 cell cats will make a significant improvement without going overboard on a daily driver.

BTW, the SAI CEL definitely DOES retard the timing! Makes a big difference whenever it is off. My fault code always reads that the ports are clogged on Cylinders 1-3, but on rare occasions the CEL will go out and remain off for up to two weeks. Whenever those periods first occur, I'll notice the additional urge and smoothness of the engine before I notice the CEL is not lit.

mongrelcat

This set of photos shows the normal sequence;

0:00 - cold, stopped




0:00 - started, idling




0:07 - parked, idled ~1 minute





0:15 - underway, thermostat has already opened -- of course i missed that shot, see last two shots (out of sequence)




0:20 - parked, idled ~2minutes




1:00 - parked back at home, idled 1 minute, level gauge shows the natural "full" point for my car




here's the point at which the thermostat opens, right around 12-15 minutes into a drive at the current 40F around here.




... and 10 seconds after that, at what I would consider highway operating temps

AOW162435

No thoughts, but I dig your screen name: Forest Devil


Andreas

Garth S

If the oil thermostat fails closed, no gurgle & oil overheats ...


If it fails open, sounds like your car ....


~$45 in parts to repair ....928 oil thermostat Drain the reservoir, remove circlip on thermo housing, and note order and orientation of 2 springs & valve (drum) as they launch out.

Yes, a 928 part ---- when they fail on a 928, it leads to low oil pressure - re plumbing differences in wet vs dry sump systems.


Anyway, a cheap & easy DIY - the springs fatigue over time, and that's 123K miles of 'time' in this case: if it does not solve the problem, at least nothing gets harmed.

e9stibi

How can someone verify that the thermostat is the issue (in this case failed open)? Another thread on RL claims that this sound is normsl:

https://rennlist.com/forums/993-foru...rculating.html

Allen

I too was inclined to call it normal except for this fact. I believe that anytime you hear/feel your car doing something different...then a second look is most definitely in order. I have no dea what might be out of order...but definitely think it needs to be checked out. BTW...how long have you had the car...ie..are you real sure that this noise/sound is not normal for your car?

TMc993

+1...No matter what others say, if something happens that isn't "normal" for your car, you need to have it checked out.

AOW162435

A graphic example of why Rennlist is a special place...


Andreas

Stewart

The gurgling noise has happened with both of my 993's (C4 and turbo). It takes perhaps 30 seconds as I drive away for the noise to disappear. I tend to notice it usually for a couple of months after a service, which for me equates to the coldest part of winter here in the UK. Many, many UK 993 owners report the same noise and it seems to be pretty random - on my C4 it stopped happening for a couple of years and then came back. I understand that my local indie checked with Mobil when it started happening to his customers, but they could not offer an explanation. It seems so common that I think in the UK at least it is being put down as 'normal'.

Cristel993

I bought my car in February last year and she was due for a service in a few thousand miles. I didn't notice a gurgling noise until after the service, which was initially concerning. I wouldn't describe it as loud; it would be inaudible if there was a conversation happening in the car when idling.

After asking what it might be I received the same feedback - that it's normal to hear at times. After a couple of months the noise went away and hasn't returned since.

She's due for another service in March, so will let you know if the noise returns.

Bouzoukikid

Same here. I here gurgling for a couple of minutes. I've read quite a few threads that this is common and normal. Noise completely goes and all my gauges are where they should be. (Uk car).

Garth S

Not my experience, but glad to learn something new! The only time I hear the gurgle/"water fall cascade" is after the car is well warmed up and slowing down from brisk use .... the thermostat is then open and oil is in full flow to the front heat exchanger.

As in Mongrelcats pic sequence, the thermostat should remain closed on start up ( to allow fast initial heating of a limited volume of oil to allow the erngine to achieve ~88C core temp) - and is quite evident when it opens, as the oil temp dips sharply form its initial rise as cold oil is introduced to the total volume in circ. In my car, this takes 12-15Km of modest driving on a cold engine.

The real test of this is to monitor the oil temp gauge sequence as nicely shown above - If it takes excessive time for the temp gauge first rise - and fall, I'm still sticking with fatigued springs in the Tstat ( = a tstst not fully closed) - if not, ?????

Waldteufel

Thanks for the progressive shots of the guages. Nice to see a non-illuminated CEL! Definitely sounds like I need a new thermostat....thanks guys!

I'm the original owner of this black/cashmere C4S, so I'm well aware of anything out of the ordinary. The car has always been dealer serviced, but I've shifted loyalties to a new (porsche only) dealer recently moved into town. I ordered the car with only sport seats, motorsound, and deleted the sunroof (for extra headroom) and rear model designation. Wish now I'd ordered full black leather and trip computer. I drove an 89 944 for 100k miles before this and lusted after a 968, but the cancelled that model before I could catch up with it. The C4S hasn't been a bad substitute! So far only the SAI CEL, a few thrown belts and a self-destructed fan have been the only real problems. But I must say the window lift switches and front and rear gas springs are nasty pieces of junk. Heading into the shop in 2 weeks for valve guides, SAI port cleaning, cam box cover gasket, oil cooler thermostat, yet another set of gas springs, and low-restriction cats.

Actually, I have had a vexing stalling problem since the car was new whereby the car acts like it has a LWF and stalls when the rapidly dropping RPMs drop below idle threshold when the clutch is engaged, or sometimes even when backing completely off the accelerator. But I'll address this in a new topic.

Did all my own work on my VWs, fluid changes and other routine maintenance on my 944, but very little on this 993 (difficult engine access and no longer equipped to get under car).

AOW162435

I left a 'Visitor Message' for you.


Andreas