911SC running hot in traffic

[francesconyc]

So im starting to learn about CIS and iim getting to know my car better.

My car oil tempi seems to be too hot around the second mark (120 celsius) when i drive in traffic for an hour

But as soon as i cruise on highways or avenues the temp goes visibly down back to the first mark or even lower if I keep speed above 40mph.

My car is 82Sc and i have a radiator (not the trombone) in my right fender. It looks like a horizontal fins style. maybe PO upgrade it, not sure, but I know PO installed an anti-drain valve in the oil line.

So why only in traffic is getting hot?

I read it could be:
- the main fannot cooling enough? it seems running well to me (PO replaced the belt recently, maybe they used the wrong one and the fan is not fast enough??
- running too lean?

My RPM when warm are around 910-950rpm when car is warm

Also fyi I added cooling collar around the fuel filter

What else cab i need check? or is just normal?

Thanks

[AndrewCologne]

If your SC was build for the US marked ... then it comes with a lambda control an also a dizzy with two vacuum connections. The vacuum connection at the inner side oof the can is for ignition retard at i.E. idle, not at regular driving, here the regular ignition advance is present. Retarded ignition at ATDC makes engines running hotter and so if you drive more with stop an go or even longer idling, your engine gets hot.
So with an US SC disconnect the inner vacuum hose, then the idle rpm rises, and here re adjust the adle to approx. 900 rpm and see if your engine will be cooler at traffic driving.

But ... beside the sense of less HC emissions resulting with retarded ignition advance at idle also the exhaust flow will be less hot and therefore the original "unheated" one wire lambda sensor will result cooler wich could make let the sensors initialize and work slower

[francesconyc]

yes, im in US/ 911 US model with O2 sensor/catalytic

im not sure if I understand: which vacuum hose are you referring to? the one from when WUR to the airbox?


(im also thiniking to upgrade the CDI with a modern MSD digital 6AL... I wonder if that can help adjust all these factors...)

[porsche930dude]

Does the fender cooler have a working fan on it? They dont work well at low speeds without the fan going

[francesconyc]

are you referring to something mentioned here:
https://rennlist.com/forums/911-forum/330473-timing-advance-on-78-sc.html

funny, I never noticed those hoses. need to take a look tomorrow and test your idea

[francesconyc]

Originally Posted by porsche930dude

Does the fender cooler have a working fan on it? They dont work well at low speeds without the fan going

I don't see a fan visually. maybe is on the other side? i doubt I have it though.

it's pretty clear to me, especially after driving today in a mix of city/highway that the problem is only in the city/idling

[garment]

Check the engine tin gasket that runs around the engine bay. Most important is the rear-most portion, make sure it’s properly seated and with the engine tin between the two gasket flaps. Without this all the hot air from the exhaust and radiating from the engine gets sucked back into the engine fan. No bueno.

[francesconyc]

Originally Posted by AndrewCologne

So with an US SC disconnect the inner vacuum hose, then the idle rpm rises, and here re adjust the adle to approx. 900 rpm and see if your engine will be cooler at traffic driving.

which of the two hoses is the "inner vacuum" RED or BLACK?
you mean more internal, close to the engine?
after I disconnect the hose do I keep it disconnected forever?


how much do I need to turn the idle screw? it feels I can dot it with my fingers, but I have no idea how much to turn each time
(keep in mind I'm working by myself, I don't have a friend to tell me inside the cabin when I reach 950rpm)


here a pic of my engine:

[francesconyc]

Originally Posted by garment

Check the engine tin gasket that runs around the engine bay. Most important is the rear-most portion, make sure it’s properly seated and with the engine tin between the two gasket flaps. Without this all the hot air from the exhaust and radiating from the engine gets sucked back into the engine fan. No bueno.

interesting, never noticed the gasket you mention

FYI I have a whale tail and I wonder if all that AC radiator is actually blocking air instead of helping with anything...

[Mark Salvetti]

The other thing to check are the oil lines running under the right rocker to the front cooler. Does any portion looked crushed? Not unusual for someone to lift the car with a jack in the wrong place and crush the lines. That would reduce oil flow to the front cooler.

Mark

[mikesarge]

If you’re driving around with the hose between the shroud and blower fan missing as shown in your pic there, you’re greatly diminishing the cooling-ability of your fan, and you’re blowing warm air around your engine bay rather than through your engine to cool it- I’d fix that asap.

[garment]

+1

Originally Posted by mikesarge

if you’re driving around with the hose between the shroud and blower fan missing as shown in your pic there, you’re greatly diminishing the cooling-ability of your fan, and you’re blowing warm air around your engine bay rather than through your engine to cool it- i’d fix that asap.

[francesconyc]

Originally Posted by mikesarge

If you’re driving around with the hose between the shroud and blower fan missing as shown in your pic there

oh sure, the hose was missing because I was working on the o2 connector.

but honestly, I'm sure I had the overheating problem since day 1 when I got the car, even before removing it.
I'll put it back and keep an eye on it, nonetheless.
I can also test it by keeping the blower motor (DEF) on all the time to see if it moves the hot air away from the bay

[Schulisco]

Agree with Andrew, had the same issue years ago. It was the distributor not advancing/retarding correctly any more. A too late ignition timing causes massive higher engine temperatures. Check the ignition timing and the distributor itsel asap! Get a digital timing light to be precise as much you can go.

Thomas

[francesconyc]

Originally Posted by Schulisco

Agree with Andrew, had the same issue years ago. It was the distributor not advancing/retarding correctly any more. A too late ignition timing causes massive higher engine temperatures. Check the ignition timing and the distributor itsel asap! Get a digital timing light to be precise as much you can go.

Thomas

I can order a timing light on amazon today

so should I follow the Bentley procedure for it?

[Schulisco]

Originally Posted by francesconyc

I can order a timing light on amazon today

so should I follow the Bentley procedure for it?

Yes, page 280 and following. Watch out for the correct ignition timing of your engine, refer to the engine type number of your's (yellow):



(Green is the serial number)

You'll find the engine specs incl. ignition timing for your SC here:

https://porschecarshistory.com/wp-content/old/Techspec/03/911-all-78-81.pdf

The 911 workshop manual contains also the igntion timing curves and almost everything else you'll probably need to know, avauilable on the net.

My recommendation: Order a timing light which with digital display which is capable of adjusting the ignition timing grade by grade, they're far more easy to handle and much more precise.

Thomas

[Mark Salvetti]

Originally Posted by Schulisco

My recommendation: Order a timing light which with digital display which is capable of adjusting the ignition timing grade by grade, they're far more easy to handle and much more precise.

Thomas

This Innova 5568 is pretty highly regarded: https://www.amazon.com/dp/B000EVU8J8/ref=sspa_dk_hqp_detail_aax_0?sp_csd=d2lkZ2V0TmFtZT 1zcF9ocXBfc2hhcmVk&th=1

Mark

[francesconyc]

Originally Posted by Mark Salvetti

This Innova 5568 is pretty highly regarded: https://www.amazon.com/dp/B000EVU8J8/ref=sspa_dk_hqp_detail_aax_0?sp_csd=d2lkZ2V0TmFtZT 1zcF9ocXBfc2hhcmVk&th=1

Mark

yep, I ordered the black model... do I need the Dwell check (red model 109$) or is it useful only for -1979 models?

https://www.amazon.com/gp/product/B000EVYGV4/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

[francesconyc]

Thomas (Schulisco)
when you had this problem, did you also have concurrent other symptoms?

I'm asking, because in my case, the only problem is just oil temp at 10 o'clock when idling (or stop-n-go) for 30min or more

otherwise, the car runs great, with great response/acceleration/ no sputtering etc.
Sure, I do have some "re-start when warm" issues sometimes but I wonder if it's correlated or not

[darrin]

francesconyc -- the higher temps you're seeing while idling in traffic are not far from normal, especially if they come down after you get out of traffic. See, e.g. https://rennlist.com/forums/911-forum/325884-normal-oil-operating-temperature.html. -- Adding a fan to the front oil cooler could help with flow at slow speed --