Duggie

Could someone tell me if the oil thermostat is serviceable or not ?? lm having issues with oil temp, i called a specialist who thinks the thermostat isn't or possibly isn't opening fully.
Issues are the temp rises enough for the oil light to come on when stationary, once moving all is fine the gauge then reads about 8 o'clock and stays there until stationary, then up it goes. lve changed the fan ballast because the slow speed wasn't working, so thats eliminated the fan.
Oil level is 3/4 up on the dipstick, oil pressure is ok, but for some reason the oil temp is creeping up and before the fan can kick in the oil warning light is coming on, any advice please??

JB 911

Does your oil temperature take 'the dip' as it warms up (the typical behavior as the thermostat opens) or does it just go straight up?

"lve changed the fan ballast because the slow speed wasn't working, so thats eliminated the fan."

I'm not sure that's positive you have eliminated the fan system completely. It should come on low speed around 9.00 O'clock Does the thermostat blow right thru 9 and nothing happens? Have you tried switching the relay with the ac condenser fan? They are the same?

thedealmaker

Not uncommon for oil light to come on when hot at idle. From page 58 of my 1995 owners manual" when the oil is hot, the red oil pressure warning light may light briefly at idle without endangering the engine"

JB 911

Interesting. My oil light has never come on even idling at +/-100F 39C. (which obviously I prefer not to do) I guess the question then is this new behavior, in which case I would think this is a new symptom.

When I read this

"once moving all is fine the gauge then reads about 8 o'clock and stays there until stationary"

My hunch from this statement would lead me to think your thermostat IS working. Obviously you are getting cooling benefit while moving and that wouldn't happen if the thermostat stayed shut.

But that said, I wouldn't fool around with engine temp. If you aren't positive, I'd flat bed that to my favorite mech.

Duggie

The gauge blips on warm up, i.e drops briefly then continues to normal, which indicates the thermostat is opening, but is it opening fully and at the right temp?? which is why I asked if they are serviceable? do they have replacement parts?
The issues begin when the engine is up to temp and car is stationary, the temp creeps up slowly past the 9 o'clock at which point the light comes on. Using 10/40 oil (lm in the UK), which is changed religiously at 5k, also noticed the idle speed drops slightly when at the higher temp (no air con fitted) if the engine is revved the light goes out, so maybe the idle speed is at fault ?? or if the temp didn't get so high in the first place the idle wouldn't drop ?? my head hurts !!!!!

LexVan

Yes, the thermostat is a serviceable part. Yes you are also using the wrong oil viscosity. Should be using 20W50.

Duggie

Here in the UK I don't think many use 20/50 in 993's, just doing a search on google and it seems 10/40 is the choice of most in the UK.

timothymoffat

With all due respect and hopefully without starting another oil fight, the two highlighted statements are your opinion. There are MANY varying opinions on oil as I'm sure you're well aware.

LexVan

With all due respect, when you know more than Steve Weiner, please send me a PM and let me know. Thanks.

timothymoffat

To the OP, when the oil light comes on, what does your oil pressure read?

Also, you said that once driving the temp returns to normal, does this happen quickly or does it take a longer period of time? Having had the oil cooler fan resistor replaced, did you confirm the low speed fan was now working (I'm wondering if the relay has failed)?

timothymoffat

I never claimed to know more than anyone on this subject, just that there are a ton of opinions on oil viscosity and brand and there are also quite different climates in which these cars operate around the world. Thanks.

Duggie

Don't want to get off track from my original post and query, lm no expert but there are many factors to which oil you use, from country climate to the engine condition. If my issue could be resolved by changing to a different oil then great, if its that simple then lm ready to change.

LexVan

Thanks, Tim. Sorry. It's all good.

timothymoffat

No offence taken.

I've come to the conclusion that discussing oil is similar to religion and politics!

Duggie

when the temp is at its highest (between 9 and 10) the oil pressure reads about 1.5 which is low, but the idle revs by this time are also lower than normal, once driving the temp goes back down gradually to normal,, the oil pressure is fine once driving, under acceleration will hit 5 and drops to around 3 to 4 under normal driving. The mileage is 97k