Tamaren

So my '81 is acting up- sorta. With it becoming summer in phoenix here, I've been running on the warm side.

-What it's been doing-
It slowly climbs in temperature until the upper white line when the other electric fan kicks on and then stays there. Which is fine, except that heats up my oil and causes low oil pressure. Which is bad. It never goes above that line, and the temperature of the heads never exceeds 230 degrees.

-What I have done-
Brand new thermostat from Porsche
Biiiiig electric fan in factory shroud
Fresh radiator flush, cleaned out. Temp is even across radiator.
New water pump
new fluid and everything like that.

So what is the problem? It's also over 100 degrees every day, I just want it to cool. Thanks!

Speedtoys

Thats normal high temp.

You're not overheating.

Tell is more about the oil you use....

Tamaren

Fair enough, I would just feel better if it would stay at a center temp.

When I was in Colorado for the winter, I put in a fairly light mobil 1 because it's really damn cold and I wanted something that would flow a little easier in cold weather. (-20 degree weather). When I came back down to phoenix, I haven't changed it. So I need to go to a heavier oil. Correct?

The Forgotten On

Yes, 20W-50 is a standard for warm climates and even heat soaked in 110F heat you shouldn't have lower than 2.5 bar pressure with good oil at idle.

The owners manual has a page just for oil weights depending on climate.

I use Valvoline VR1 20w-50 in my 81 here in SoCal. Although it is no longer sold in CA it might still be available in AZ though.

The main thing is just to be sure it has enough zinc.

ammonman

If you use the VR1 be sure to change the oil more often. Racing fluids generally have less robust detergent packages than street oils since the expectation is they will be changed every race or two. Consequently the oil doesn't collect as much moisture and contaminants so the detergents can be reduced vs a street oil. Racing oil additive packages are generally much heavier in anti-wear components to ensure component life.

Mike

FredR

As has been stated, when operating at your ambient temps the motor was designed to run on a 20W50 with good ZDDP levels and should typically indicate 2 barg at hot idle. Start running witch **** thin oils designed for modern motors at those temps and the indicated pressure will easily drop to 1 barg at hot idle.

Running at or around the last white line is perfectly normal, the thermostat starts to open at 83C and as I remember is not fully opened until around 90C. Some models exhibit slightly different characteristics but I put that down to calibration of the instruments.

The cooling capacity can be improved a bit by leaning out the coolant mix to say 33% or even 20% but if you do this you should also add some Red Line water wetter that helps heat transfer but just as importantly, has an anti corrosion chemical additive package. Needless to say a leaner mix will also change the freezing point so mix to suit your coldest exposure temps.

Beyond that change your coolant every two to three years. You can also lab check the condition of the coolant to help determine suitable change intervals

SeanR

That's your problem right there.

928NOOBIE

+1

I use Royal Purple HPS 20W 50. It has higher levels of zinc and phosphorous for our style of valve trains and is a full synthetic.

I also use a product called Hy-Per lube for same reason as our cars need zinc in their oils...to stick to the valvetrain. Running a bottle of hy-per lube makes a difference even with the oil I use. Upper rpm vibrations are much lower...engine is noticeably smoother....

BrianG

You can also get a lower temp fan switch. Find one from an early VW Golf I believe. There are a variety of temp ranges available.

GregBBRD

I don't generally get involved with these "generic problem" threads....unless I see something obviously missing or incorrect.

I'm not sure your problem is just thin oil...although that definitely needs to be changed.

I do not think the extra electric fan should be coming on in 100 degree heat. Does the electric fan come on, cool the car down, and shut off? From what you have written, it doesn't sound like it does.

These early cars have a belt operated fan mounted onto a fan clutch. The clutch doesn't spin the fan as much, when the radiator is cold, but increases the amount it spins the fan when the radiator gets hot.

If the special fluid in the fan clutch has gradually leaked out, over the years, the fan will never work enough to cool the engine. The clutches get so weak that they do virtually no cooling and the car ends up depending on the electric fan to cool the radiator.

If you have an air compressor, get the engine hot and blow air backwards on the fan. If you can stop the fan with air, the clutch is bad. (When the clutches are really bad and it is obvious, I sometimes just reach in and grab the fan...stopping it. This takes some experience.....I would not suggest you do this, at home.)

There's instructions on this Forum for filling the fan clutch, if it is still good and just low on fluid. These good people can guide you towards that/those threads.

KenRudd

This test right here:
"f you have an air compressor, get the engine hot and blow air backwards on the fan. If you can stop the fan with air, the clutch is bad"
just made my day. I had been wondering how to authoritively determine the state of my fan clutch. Thanks Greg!

Richard S

Blow all the crap out of the radiator fins. If it has never been done, it is full of 36 years worth of dirt, sand, bugs, dust, leaves, etc etc.

Drain and pull radiator then use compressed air to blow out the crap from back to front. Clean out all the accumulated crap between radiator and A/C condenser. Then use compressed air to blow the same kind of crap out of the condenser from back to front. While the radiator is out straighten any bent fins. All this should improve the airflow and cooling.

Worked wonders on my old 79 the first time I did it.

Rich

Landseer

My ljets and 85/6 cars rarely run much above 1st white line.
Albeit, its not 128F ambient anywhere ive driven.

If needle rises at slow speed or when parked, then drops a bit when at speed, fan clutch refill nec. I've refilled a few and they work great. Fluid is dimethicone, aka linear silicone, any where between 6000 and 10k cps. Toyota may still sell it, though overpriced, to refill fans. Others here say get r/c car differential fluid from hobby shop. Syringe with a basketball inflate needle force threaded on end will be needed to reach into the fill hole and depress the valve,iirc.

jwillman

Been there and done what you have and then some. My car was going above the second white line at stops during the Texas summers which don't compete with your conditions!

Your post does not mention situation you see these temps so I don't know if the concern is slow traffic and idle or all the time. I had read in a few posts that cars should not need the fan when vehicle is up to speed so it would seem that at 60 MPH if your still at the same temp as at idle the cooling system current state is working the best it can.

I attempted to refill my fan many years ago and all I ended up with was allot of the thick oil slung all over the inside of the hood and engine compartment after the first run.

I deleted the belt driven fan and installed a Ford Concour's dual electric fan I found in a salvage yard for $25. The fan assembly and shroud fits inside the lip of the factory radiator so it looks like it was made for the car. I am currently using a Hayden digital fan controller that runs both vans at progressive speeds as required. I also deleted the old front side electric fan and have the dual fans come on full time when the AC is running primarily because of concerns around 90 AMP alternator performance at idle

I took the radiator and had it flushed by a professional. Because of the venturi tube design they could not rod the radiator but where able to get me about 30% more flow, about 90% efficiency based on their assessment using a chemical flush process.

I now run mid to 3/4 range short of the second white line all the time without large swings in temp that I use to see.

I know its not stock but I also have a ton more room between fans and engine for other work and no fear of getting stuck at a stop light

z driver 88t

I often tend to take a "shot gun" approach to these problems and hit every possible cause because I just don't want to deal with multiple attempts eating up multiple weekends - granted I may do some things that are unnecessary.

The first couple years of owning my 928 it stayed right at the lower white line. About number of years ago my temp started climbing towards the upper white line while it had historically operated near the lower white line. I live in FL and while not 100 degrees, our typical summer days are mid-90s. I did the best I could to confirm the fan clutch was OK. It was hardly scientific - I had never thought of Greg's approach. I just got the engine good an warm, felt that there seemed to be good flow behind the belt driven fan - turned off the car and felt that there significant "engagement" of the fan clutch and made some (perhaps invalid) assumptions that it was OK.

I did a 928MS radiator, lower temp thermostat, lower temp electric fan switch for the front fan. Temps now stay EXACTLY at the lower white line - even more solidly than when I first bought the car. I can't tell you for sure which item played the largest role.

I'm hoping this thread doesn't turn into a 928MS pissing match thread. I did have one original 928MS radiator fail - Carl replaced it under warranty and the new one has worked very well for several years now. Whatever your choice, I know 928INTL sells aluminum radiators as well that seem to have a good reputation, should you need one. Just my experience, YMMV.

Two things in your list have not yet been mentioned, which are a lower temp thermostat and lower temp e-fan switch. Both of these are pretty cheap and worth considering, especially if you have already pulled the clutch operated fan.

Also, you may want to do a little Internet digging into the flowrate of the electric fans you are running. There is a general (and often incorrect) assumption that e-fans will consistently out-perform clutch driven fans.

You also mention you are running a big electric fan in the factory shroud. Keep in mind the fan and shroud work together as a unit. If you are running an unshrouded electric fan with the blades close to the radiator and just have it tucked inside the factory shroud you are not pulling air across the entire cooling surface and the shroud isn't really doing much. If the e-fan is mounted close to the lip of the factory shroud and the blades fill most of the void then you are at least pulling air across the whole radiator.

Most people don't go to the trouble to actually test various fan/radiator configurations, but back in my Nissan days one of the guys did some fairly in depth testing (just as an example http://texasnissans.com/tx/forums/sh...ad.php?t=10117 )

The lesson is just don't assume the e-fan you are running are better than the clutch driven fan.