SC running "too damn hot": Mechanics stumped, So am I ! - Page 3

Deschodt · 10-29-2006, 05:37 PM

Ok, not so much bumping this thread as reporting on the final "to-dos" from all of your ideas...

- New thermostat to the main cooler (engine mounted)
- Verified the flow to the front cooler
- Verified the front cooler is not obstructed = similar readings up/ down/ right/ left of the cooler
- Verified the oil lines not crimped, temps difference 20 to 30F between inflow and outflow with the fan on
- Verified timing: At Idle: 3 BTDC
At 3000 RPM = 18 BTDC
At 5000 rpm = 20-22 BTDC, matching the specs for an SC engine to the letter (what's the 36 degrees advance at 6000 rpm, mentioned by Dr Steve for? Non vacuum line distributor cars?)

- Belt was slipping a little and jumping a little at high rpms, put fresh one on the car
- New temps activated ft cooler fan instead of hand switch
- Put in a new temps sender tonight, and verified the old one worked as a charm ! If anything it read a few degrees low, not high !

Results: not much. The automatic fan is a bit better as I can set it up to engage at lower temps and not "forget", so in town I am running 90C or thereabouts. On the freeway, it's back to 225-235F in no time, the speed and turbulence negates the airflow from the fan...

I could not check for rat remains on the cylinder fins, I can barely see what's behind the fan, no mirror combo will get me past the fan... My last options are the used crank pulley (134 mm dia.) to increase air flow by increasing the fan speed, and some more barricading of the front cooler so that air has nowhere else to go but through it!

Slightly dissapointed to have gained very little after all that ! ;-(

ras911 · ras911's Garage

Did Any one suggest the ,,,,,,,,Cool Collar?

Cool collar

Hope you get that sorted out . I had a red one that liked to run hot , drove it 3 seasons in DC

Bob

Duckworth · Duckworth's Garage

That's a crushing amount of time and effort for little-to nothing in return....

Your troubles are most unusual. What I recall very well on my '82 was that even at 105 F - as soon as the car hit the freeway no matter how hot it was - the gauge always backed itself down to a healthy reading. It only had a trombone cooler - which very seldom ever got activated by the thermostat.

Wonder if a motor 'swap' or drop would reveal the problem.

________________

'82 Targa - sold
'80 928

Deschodt · 10-29-2006, 06:03 PM

Well, it does have 170K miles, but I am not sure how being possibly "tired" translates into hot temps. Also, it was already doing this 70K miles ago ! And it's still running strong !

This one has stumped 3 mechanics now, not the worst ones either (some famous shops from San rafael,CA - and now my local wrench in FL)... If I ever figure it out I'll have to write a book !

dickster · 10-30-2006, 12:36 AM

Hi

It is worth checking the sump plate as others have suggested.

Good luck!

Ps You could move to a colder climate! (from the cold uk)

Noel · 10-30-2006, 02:57 AM

I still think you need to remove the fan and have a proper look at the top of the cylinder fins and most importantly on top of the on engine oil cooler to verify that air is flowing through. This is the most likely cause IMO.

scarceller · scarceller's Garage

Quote:

Originally posted by Noel
I still think you need to remove the fan and have a proper look at the top of the cylinder fins and most importantly on top of the on engine oil cooler to verify that air is flowing through. This is the most likely cause IMO.

I agree, seems like you have checked everything else. You need to be sure air is flowing through the cylinder fins and the engine mounted cooler. I think it would be wise to inspect this. As mentioned above remove the air fan as well as the covers to the left and right of the fan to get a good look at the top of the engine case as well as the air fins. I also posted earlier to be sure no one installed the air diverter sheet metal betwen the cylinders backwards, I had a 75 2.7L that someone (prior to me) had done this.

Deschodt · 10-30-2006, 05:58 AM

Ok, I will unbolt all that stuff - not sure what the air diverter should look like if properly mounted. Pictures anyone ?

>It is worth checking the sump plate as others have suggested.

I never considered that one carefully as it was for early 78 SCs, mine is 83 !

Craig 930 RS · 10-30-2006, 05:59 AM

Greg -

Please take some pictures on the oil cooler setups - in. under, around, and post them -

scarceller · scarceller's Garage

Quote:

Originally posted by Deschodt
Ok, I will unbolt all that stuff - not sure what the air diverter should look like if properly mounted. Pictures anyone ?

>It is worth checking the sump plate as others have suggested.

I never considered that one carefully as it was for early 78 SCs, mine is 83 !

Picture of access plates

Picture of Air Deverters/Baffles between cylinders

Steve@Rennsport · 10-30-2006, 07:36 AM

Quote:

Originally posted by Deschodt
Verified timing: At Idle: 3 BTDC
At 3000 RPM = 18 BTDC
At 5000 rpm = 20-22 BTDC, matching the specs for an SC engine to the letter (what's the 36 degrees advance at 6000 rpm, mentioned by Dr Steve for? Non vacuum line distributor cars?)

Greg:

IMHO, you should find someone with a distributor machine and have your dizzy checked for full advance and vacuum canister operation.

It looks like you have retarded timing at 3K to 6K and that certainly makes these engines run hotter than normal.

Deschodt · 11:39 AM

Steve, thanks for that, but the specs book for the SC says that with the vacuum lines off and plugged, those numbers that I am getting are EXACTLY the numbers I should see...

I quote: 80-83 SC 5deg +- 2 BTDC at idle , vac hose disconnected
21 +-3 deg at 6000 rpm (vac hose disconnected)

That is -exactly- what I get ! I figured that was for distributor without a vacuum system? What is the deal there ? please ! ;-)

I don't understand how to reconcile the numbers in the manual/bentley etc with that 36 degrees number...

I don't doubt you - I know better, andI'd love for this to be the problem, but it does match the manual, what am I missing here ?

Steve@Rennsport · 10-30-2006, 11:58 AM

Greg:

There are plenty of documented errors in the Bentley manuals so I'd not take everything inside them as gospel.

I WILL tell you that 21 deg at 6K is very retarded and results in excessive engine temperature. Thats a good number for a twin-plug motor,...

Deschodt · 12:12 PM

Well, it's also the numbers on the porsche factory charts...

But Ok, deal !! I will advance it more so that it reaches 35 or so, that might mean a lot more advance at idle as well... I will report on results and cross my fingers that does not break anything...

I just wanted to be sure you really meant it, on that model year, with that distributor! But Steve Weiner beats Bentley, in my book ;-)

By the way, vacuum lines pluggedf or connected?

stlrj · 12:39 PM

Quote:

At 3000 RPM = 18 BTDC

What is it with the vacuum line connected? Because if that's all you get even after the vacuum lines are connected, there might be your problem.

Cheers,

Joe

Deschodt · 01:14 PM

Well, I just did what Steve recommended ! I now show about 10 degrees at idle (had to lower it) and 35 max advance, regardless of top rpm - it never goes beyond 35deg at 5000rpm, let alone 6000...

I'll run it like that see what happens ! That was with all the vacuum junk connected !

I am baffled by the difference in specs between steve's numbers (frm experience I imagine) and the factory specs !

Stlrj, I don't know what the numbers were with the vacuum connected before this change, since I did it per the book vacuum removed and plugged, but you have what it is now... Would 12 btdc at idle be bad in ANY respect ?
It starts just fine !!

stlrj · 10-30-2006, 12:44 PM

12 btdc seems a bit high. Do you have a vacuum retard, advance or both ?

aturboman · 10-30-2006, 12:48 PM

Someone mentioned early on to check the exhaust for restriction, was this done? This is very sound advice since as the exhaust gets older you will often find the cat. convertor breaking down inside and this can cause a major restriction. On air cooled cars in particular this can lead to increased exhaust temps/engine temps. You seem to have covered most of the other bases so far, so I would suggest you get a cat bypass and or borrow another cat and try swaping it out. I'd even try to borrow another muffler as well since they also plug up over time. A customer's SC went 300+K on the original engine but the convertor was toast @ 150K miles when we replaced the chain tensioners. We put in a "test pipe" and it never ran better or cooler after that. Good luck.

Deschodt · 10-30-2006, 01:21 PM

stlrj, this is a stock 83SC, per the book I have centrifugal and vacuum advance and retard... In other words, no clue !

I read 10 degrees advance now, all connected at idle. The specs are 5+-2 at idle, vacuum disconnected, but 10 degrees all connected now, I don't think it's radical, so let's see what it does... 35 at 6000 is the part I don't know about, I showed 21 before with the vacuum lines removed and plugged. But at least now I am matching what steve recommended...

I also removed the front running light in the bumper and have fresh airflow to the cooler ! Of course if it's dramatically better now, I will be kicking myself because I won't know which of the 2 modifications did it ! ;-) But I am pessimistic by nature, I bet nothing changes !

Turboman, I've been told by the mchanic years ago that my cats have been ...ehhh, gutted by the PO, so there is ZERO restriction there ;-) Then again, maybe I should revisit waht gutted meant and take a look !

Thanks all !!!

stlrj · 10-30-2006, 11:38 PM

Quote:

35 at 6000 is the part I don't know about,

That's what you should be getting with all vacuum lines connected. Are you getting that?

Joe