SC running "too damn hot": Mechanics stumped, So am I ! - Page 5

Deschodt · 05:59 PM

>Hopefully, you will soon be able to confirm airflow thru the REAR (main) cooler. Unless you've already confirmed - have a friend hold a 2500 rpm speed and sneak your hand up to feel lots of air coming thru.

You know, I have not done that ! Underneatht he car you mean, where the cooler is partially visible ?

>MO you are ducking the most obvious culprit...air baffles and air flow

Sure, it's just that everything done so far was feasible by a guy with 2 left hands. Pulling all the shrouding to look for the baffles is not a trivial project for me ;-) But I'll try this w/e ! I promise !

>take an actual temp reading of the oil with a laser thermometer to make sure you're not chasing a ghost reading.

Done. I carried the thermometer with me for days ;-) The temps are real, thought there is not ONE single point in the engine compartment or lines that match exactly the gauge readings - it's always a bit hotter or cooler depending on location. But it's in the neighborhood, and once at home I cannot touch my rear bumper without pain! It's HOT. I've calibrated the gauge with boiling water as well, and double checked oil temps in the tank by dipping a thermometer in there! Also thereabouts, cooler, but that's not a correct location anyway !

911gone · 10-31-2006, 07:37 PM

I owned a 1983 911 SC for 11 years and fought high temps similar but not as high as yours for years. I had a turbatrol cooler installed and I gutted the cat. These helped slightly but what really helped was having the engine pressure washed when I had a new clutch installed and my trans rebuildt. Accumulated grime on the engine cooling fins over the years, that I could not see, added about 20 - 30 degrees when the engine was under load! Try it if nothing else works.

Steve W · Steve W's Garage

Either your mixture is too lean somewhere, or your vacuum advance mechanism is not working. My bet is on the latter. You've indicated previously, with advanced ignition timing, while driving under a moderated load, the car does not ping, but does so under hard acceleration. Under light loads, such as during cruise situation, the intake manifold vacuum is high, and the cylinders do not fill up with as much air and fuel. The air/fuel molecules are much farther spread apart than at full load, which would burn slower, and thus need more ignition advance (through the vacuum advance mechanism) to fire the mixture and provide peak combustion pressure at the optimum point after TDC. Typical low load ignition advance should be around 15 degrees more advanced than full loads. Therefore if full load advance at 5000 to 6000 (measuring with vacuum line disconnected is 30 degrees btdc, with the vacuum line connected, the advance mechanism should advance it a further 15 degrees for best part throttle cruise efficiency. I really do not know the actual tuning specs of a SC motor so don't take my words as gospel, but 20 to 22 degrees at 5000 with the vacuum lines disconnected seem way too low to me.

To test the funtion of a vacuum advance I'd use a Mitivac vacuum pump. However Steve Weiner said it best, if you're not sure what you're doing, get your distributor tested.

Duckworth · Duckworth's Garage

Quote:

>Hopefully, you will soon be able to confirm airflow thru the REAR (main) cooler. Unless you've already confirmed - have a friend hold a 2500 rpm speed and sneak your hand up to feel lots of air coming thru.

You know, I have not done that ! Underneath the car you mean, where the cooler is partially visible ? ...Deschodt

Yeah baby ! ....although I'm making it sound like a piece of cake - it may not be. With so much air swirling under there and limited access for your hand - it may be easier to hold up a scrap of cloth with skinny extended pliers to 'see' the evidence of flow. Or..., a 3/4" rubber hose held up flush to the cooler and hand at the bottom of it to feel for air pressure.

________________

'82 Targa - sold
'80 928

Deschodt · 11-01-2006, 04:32 AM

Quote:

Originally posted by Steve W
Either your mixture is too lean somewhere, or your vacuum advance mechanism is not working. My bet is on the latter. I really do not know the actual tuning specs of a SC motor so don't take my words as gospel, but 20 to 22 degrees at 5000 with the vacuum lines disconnected seem way too low to me.

Thanks, that was a good explanation ! Actually, 20-22 degrees with the vacuum lines disconnected IS the porsche specs for an 83 motor ! Surprisingly low, huh ? A 78-79 motor would be 26 !
I really need to measure what that translates to with the lines ON, I was too embarassed to do so last night (halloween - me revving the crap of the motor and scaring the kids)

I've had issues last night on my way home with the very advanced timing, so I eyeballed it back by the side of the road, and then when I got home it turned out I did it perfectly. A little bit more advanced that stock (2 deg), but not quite as much as yesterday. No pinging, no problems.

The temps decrease I saw yesterday morning was not all that significant after all (realize this is a bit empirical), it was very close today, and it'll be back to normal (hot) this evening I am sure. I plan to get the distributor cleaned, tested if I can find a local guy ( I need my car - unless the Don MArks of this world provide exchange units, I cannot lose my dizzy for a month), and I'd love to have the motor cleaned but that is a big engine out job. I'll price it, see what happens, that'll make checking the baffles super easy ;-)

scarceller · scarceller's Garage

Quote:

Originally posted by Deschodt
>Hopefully, you will soon be able to confirm airflow thru the REAR (main) cooler. Unless you've already confirmed - have a friend hold a 2500 rpm speed and sneak your hand up to feel lots of air coming thru.

You know, I have not done that ! Underneatht he car you mean, where the cooler is partially visible ?

>MO you are ducking the most obvious culprit...air baffles and air flow

Sure, it's just that everything done so far was feasible by a guy with 2 left hands. Pulling all the shrouding to look for the baffles is not a trivial project for me ;-) But I'll try this w/e ! I promise !

>take an actual temp reading of the oil with a laser thermometer to make sure you're not chasing a ghost reading.

Done. I carried the thermometer with me for days ;-) The temps are real, thought there is not ONE single point in the engine compartment or lines that match exactly the gauge readings - it's always a bit hotter or cooler depending on location. But it's in the neighborhood, and once at home I cannot touch my rear bumper without pain! It's HOT. I've calibrated the gauge with boiling water as well, and double checked oil temps in the tank by dipping a thermometer in there! Also thereabouts, cooler, but that's not a correct location anyway !

You do not need to pull all the shrouding. The left side access cover (Behind Distributor) is the harder one to remove, I suggest you start by removing the right side cover it has 3 or 4 10mm screws and it's out. It really is easy to remove and once removed you will see the Air Baffles between the cylinders (cyl 4,5,6) they should be inserted between the cylinders from the bottom of the engine (they go in from the exhaust side) just like in the picture below with the tin strips holding them in place at the top of the cylinders. Here are the pics once more.

Deschodt · 11-01-2006, 04:48 AM

Thanks ! Somehow this explnation makes it sound easier than the first ! I will do that tonight, and also measure advance with the lines on ! For grins ! I'm gonna win this fight ! I'm stubborn enough !

scarceller · scarceller's Garage

This may seem very basic, but no one asked: What oil filter are you using?

Deschodt · 11-01-2006, 05:06 AM

standard german fare... I forgot but mahle maybe ? It's the one you get from most players, this one from pelican...

scarceller · scarceller's Garage

Quote:

Originally posted by Deschodt
standard german fare... I forgot but mahle maybe ? It's the one you get from most players, this one from pelican...

Sonds fine, just thought I'd ask.

WERK I · WERK I's Garage

Greg,
Glad to hear the temps went down with timing adjustments. Regarding your front oil cooler additions. Are your using two oil thermostats? One back by the right rear wheel well and up front? If so, why?
Secondly, are you using the stock oil lines at the rear wheel thermostat or have you added braided oil llines to your car?

Deschodt · 11-01-2006, 06:33 AM

Quote:

Originally posted by WERK-I
Glad to hear the temps went down with timing adjustments. Regarding your front oil cooler additions. Are your using two oil thermostats? One back by the right rear wheel well and up front? If so, why?
Secondly, are you using the stock oil lines at the rear wheel thermostat or have you added braided oil llines to your car?

Well, the temps went down but the car also pinged and ran like crap later on, so I would not call that a success necessarily. Also, since the car does not have a knock sensor and not all pinging is audible, I hesitate to play God with my timing anymore... I am currently on the upper side of the range supplied by the factory... Good'nuf, I will have the dizzy and vacuum checked anyway !

2 oil thermostats ? No, one for the oil cooler, the second is for the fan that I installed on the oil cooler and determines when it triggers. ;-) Sorry about the confusion !

Stock lines, yes.

I think we've gone around the problem now - once the dizzy is checked as well as the vacuum advance, the air diverters and the cleanliness of the motor, we should have an answer. If all is well and it still runs hot after all this, I swear I will put black tape over the temps gauge and rive the car to the ground ;-) It worked on my ex- 356s ! (ignoring the temps, I mean)

Zeke · 11-01-2006, 07:10 AM

Can you borrow a distributor from another SC? What does the parts dismantler in your area get for one of these? You seemed to have discovered a path to the correction, now the proper correction is in order.

Also, you seem to have not accomplished to full inspection to the top of the engine. A lot of these engines just get plugged up with oil and fuzz from who knows what. You can take an air nozzle and from the bottom between the baffles, blow air upwards. If you see debris coming out of the fan, you know what you have to do next, get that fan out of there and get some access to really see all 6 cylinders. And, if you have "fuzz" on your cylinder fins, you also have it on your engine mounted oil cooler. I've seen VW engines blocked nearly solid with caked and baked oil mixed with "fuzz."

Noel · 11-01-2006, 08:26 AM

Most of the cooling comes form the main On-engine oil cooler (Not to mention cylinder head cooling). I still say that you don't know anything until you pull the fan and take a look....

911pcars · 11-01-2006, 08:29 AM

This may have been covered on page 1 already.

What is the heat range of the spark plugs? You don't want hotter plugs installed.

Sherwood

Deschodt · 02:46 PM

Tonight's update to this unending saga !

If you ask me, it looks pretty damn clean for 170000 miles !

There is a piece of a leaf in the back, very small, and a tiny feather in front - sorry about the picture quality but it's hard to focus in there...

The diverters don't look upside down though !

Bam, just like that, I am left with the distributor, possibly, and that's pretty much it. Ok I will pull the fan and look at the other side as well ;-)

PS: sherwood, no idea about the plugs, I guess I'll pull one, but I am pretty sure they are correct...

Mysterytrain · 11-01-2006, 04:00 PM

I mentioned this about 40 pages ago...and no one commented on it, so I'll try again.
As we all know the external thermostat housing has a thermostat that controls flow to the external cooler but there is also a pressure piston on the bottom of the housing. I'm not sure of the function of the lower piston but I would imagine that if it hung up it would restrict the return flow of oil. Any thoughts on this??

Also, wasn't there an issue with external coolers. Something about an internal baffle missing??

Good thread

Noel · 11-01-2006, 05:48 PM

The cylinders looks good. Were you able to get a mirror back near the internal cooler to look for nests or dirt collecting on an old oil leak? If you didn't see anything, then you are probably OK there. DAMN!!! I was hoping it would be that simple for you. Sorry.

Mookster · Mookster's Garage

Just out of curiosity does your vehicle have the sump plate at the bottom of the engine case?

If so, is the oil drain plug on the left side?

If you have a sump plate and the oil drain plug is not on the left side the drain plug will interfere with the oil pump...reducing oil flow creating heat.

Just a thought.

(If you have a later production year the case drain plug is on the left and there is no sump plate thus a non-issue)

I second check the plugs for correct type. Replace them regardless.

Deschodt · 11-01-2006, 06:51 PM

Yes to the sump plate... Yes, the plug is on the left (driver) side of the plate.

>Replace them regardless.

With what ? Any specific brand/type you can think of that promotes running cooler? Thanks !