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

[dickster]

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 !

Never take it for granted that you have the later one! It is worth checking to be sure.

[Deschodt]

Joe, yes I am getting that now (I don't know if I was getting it before, though, since you are supposed to measure 21 with vacuum lines off and I did not remeasure with lines on)..

Ok, results as of this morning :
Bumper "city light" removed for better airflow, and timing advanced to 35 @ 6000 rpm (35 is max advamce anyway, I reach it at 5000).

The car runs significantly cooler, in town and on the freeway, say 20F cooler easy ! The fact that is runs cooler in town where airflow from the front bumper is not as great seems to confirm the timing helps... Also took longer to reach 90C than it normally does, which also helps the distributor cause !

BUT.... Big but !!

If I accelerate hard though 4000 rpm (2nd gear), the car makes a rattle sound that can best be described as a playing card through bicycle wheel spokes. Not sure if that is pinging, but it's a sound that was not there before the adjustment. Almost like an exhaust rattle.

If I accelerate slowly though 4000 rpm, no problem at all...
Is there some other adjustment I need to make to the mixture or something to compensate for the new timing ?

I am tempted to revert back to normal factory specs tonight and reconfirm no noise at that RPM (only when accelerating hard) and retest just the bumper opening anyway... As a service to my fellow hot running SC pelicanites ;-) Opinions welcome !

[Deschodt]

Lovely ! Is it OK to assume that if I don't get on it too hard, I can drive home safely and not do damage ? It only does it under hard load !

[stlrj]

That rattle could be a broken head stud.

Joe

[Deschodt]

Well, too much of a coincidence to be a broken head stud, I think !
The car does not make the sound if I slowly (or normally) accelerate through the RPM range, only if I get on it HARD.

Sounds to me like the distributor is slow to catch up in the middle of the curve! But what do I know ?

Problem: I drive this car a lot. sending it out (generally to the weat coast) will leave me without a car for a month, easy !
Replacing will set me back $930 per pelican's refurb ones ! Options ?

[Duckworth]

Put back the distributor as it was - doubt that's the problem. If the return springs are sticking there are ways to lubricate them.

My '82 was super sensitive to knocking and pinging when I attempted a small increase in the advance. (As you found out also.)
Incredible how easily it would 'ping' in 1st or 2nd as I went from
5 degress BTC - to 8 degrees idle setting. Uhm.., 8 degrees BTC detonates a mild SC motor ??? Anyone explain that ?

One thing I did was scratch a little line next to the nut that tightens down the distrib so that you have an easy reference to put it back to the correct spot when messing around with it or out on the road.

...The time draws near for you to get inside the motor.
_______________

'82 Targa - sold
'80 928

[Deschodt]

>The time draws near for you to get inside the motor.

Since you're going there... What would you expect to find inside the motor that would cause higher temps ? Broken rings ?

Why would other SCs on this board run fine with 35 degrees advance and 12 at idle ?

>Put back the distributor as it was - that's not your problem.

Well, maybe... But it does run very smoothly and much cooler right now with that advance, pinging excepted ! ;-) I will have the distributor looked at anyway to be 100% sure. It looks lazy to me, because I have no pinging -at all- if I rev the car normally, but it pings if I stick my foot in it - that suggests to me the little dizzy is not keeping up... But what do I know ? ;-) I'd be happy not to have to get a $930 new one or a refurb, that's for sure.

I'm going back to stock timing tonight, and will leave the notch in my bumper open to see the effects in isolation anyway !

[911pcars]

" I will have the distributor looked at anyway to be 100% sure. It looks lazy to me, because I have no pinging -at all- if I rev the car normally, but it pings if I stick my foot in it - that suggests to me the little dizzy is not keeping up..."

Detonation usually occurs under load, moreso than in a low-load condition. That tells me your ignition timing is too far advanced for that rpm, or (here comes the list) ambient temp is too high, unsufficient fuel octane, rpm too low for load, compression ratio too high, A/F is lean, timing too far advanced, engine is overheated, etc. or any combination therof. In addition, all these conditions are interelated. One condition can cause another which exacerbates the symptom.

Sherwood

[Deschodt]

Ok, scratch that then ;-) Thanks Sherwood !

Back to factory settings tonight (Sorry Steve W. I'll still have the dizzy checked for sanity)...

I am losing patience anyway. I have run it 70K miles like this and it's still running, I guess I'll burn this motor down the way it is ! It might be cheaper than to replace all the potential "running hot" causes ! ;-) I think I've done pretty much everything except the dizzy and checking the air diverters between the fins (oh and that sump thing but I don't quite know how to check that one)!

[lateapex911]

Sherwood has it nailed. Factory units from later cars are often constantly adjusting timing on the edge of pinging. Thats what a :"knock sensor" is. Part of the plan! You just took a big jump, so why not try the middle ground??

Also, hi octane fuel ,,,93....helps out a lot. So, make sure the tank is full of the good stuff, then adjust the timing incrementally until the problem stops. It is most likelty to occur at large throttle openings, and usually at lower revs. So in third gear, when you go from a light throttle opening at say 2500 rpm, to wide open will probably bring on the knock condition. Use that, or a similar test and repeat until you find the best combination of advance timing and no knock.

But be carefull!!!!!! Knocking is bad for the engine, and in extreme cases can crack rings and other nasaty things. So, start low ( stock or mid range timing), work up 5 degrees at a time or so,, then back off to the previous setting as soon as it happens.

[911pcars]

Thanks Jake, but it's Deschodt's situation isn't solved yet.

It'd be convenient if audible detonation was the case. Unfortunately, not all detonation is audible. I don't think SC's use a knock sensor. Someone can correct me.

Deschodt,
It might prove useful to summarize the suggestions made and your inspections and remedies to date. Maybe something obvious has been overlooked?

Sherwood

[lateapex911]

Agreed Sherwood, no auto adjust on his car. And you're right, much detonation isn't audible. But i would think that finding the limit, then backing away a bit timing-wise could get him closer and cooler.

[audi2.7t]

After following this thread for a while I have been drawn to a couple of conclusions..
1. The additional oil coolers are unable to compensate for the core temperatures which means the engine is running way hot.

2. The above indicates a lack of initial engine cooling ie. air flow, be it delivery or exhaust. The first thing I would do is make sure that the engine is getting adequat cool air... check the condensor? or even run the car with the condensor off the grille. If the engine is getting cool air, is it flowing over the heads...not just to the heads. Check air baffles, fins, engine bay seals. Blocked condensers, air coolers and radiators that visually look fine are the #1 reason for liquid cooled engines overheating, air cooled engines are the same in principal.

3. Check the entire exhaust for restriction, try a test pipe .

[TargaT]

Are you checking the timing only when it's cool? If so check if it's the same when it gets hot. My timing looked fine till the car got hot, then the timing went all to hell.

Joe

[Howard M]

Besides the very worthwhile check of the air baffles, how about pulling the distributor to confirm free motion of the advance mechanism. Puzzling that you had to "over" advance the timing at idle to get the proper timing at 6000. The over-advanced timing may be contributing to the pinging above idle. If the advance weights were free, proper timing at idle should still yield proper advance at 6K. It's an easy check to make, especially compared to everything else you've done already.

[Deschodt]

Sherwood, and others: thanks! I apologize for the lenght of this thread but I am really determined to get this resolved now !

You asked for a summary, I think I posted one the previous page, but here it is, all updated:

- 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
- Mechanic temporarily mounted a front cooler after the fender cooler and blew big air into it, it made no ignificant difference
- Verified timing: As per book, vacuum line sremoved and plugged
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
- Bumped timing to Steve Weiner specs - ended up w/ 35@6000 and 10 at idle. Can ran cooler in the morning, but it ran like crap that same evening, hesitating at constant RPMs, and pinging under heavy load. Bacl off the timing to stock. As you said Iam not a human knock sensor, better safe than sorry !

- Belt was slipping a little and jumping a little at high rpms, put fresh one on the car, all good now - zero results.

- New temps activated ft cooler fan instead of hand switch - it helps at low speeds - temps stays at 90C (first white bar) but makes zero difference at freeway speeds.
- Put in a new temps sender and verified the old one worked as a charm ! If anything it read a few degrees low, not high !

- Opened the front bumper (removed what is a turn signal for you guys - it's a running light on my car for some fortuitous reason) for airflow : bubkiss, nada, same difference.

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 220-230F in no time, the speed and turbulence negates the airflow from the fan, I think...

- The cat is as good as empty so it's not an exhaust obstruction

- The engine grill is free of stuff and I pulled the A/C anyway, free flow

To do still: look for the baffles/air diverters etc...(not exactly easy) get distr checked... duct air to the fender cooler from my bumper opening...

[Duckworth]

- Verified the flow to the front cooler...

- Verified the front cooler is not obstructed..

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.

______________

'82 Targa - sold
'80 928

[JP911]

35 total advance seems really high for a stock SC. That's the timing used with a carbed engine. You should stick with the factory recos on timing unless you're running high octane fuel.

[audi2.7t]

IMO you are ducking the most obvious culprit...air baffles and air flow. All this "Opened the front bumper " and "added extra cooler" are not addressing the problem. You need to verify air flow over the cooling fins. The timing (I'm pretty sure)is not the problem, all your extra bandaids would have compensated for this. One other thing that maybe you should do, once the car reaches high temp on the guage take an actual temp reading of the oil with a laser thermometer to make sure you're not chasing a ghost reading.

[patkeefe]

Greg:
I applaud anyone who can make this kind of effort in troubleshooting. Here is some light reading; I think you are on the right path regarding ignition timing. Have you checked your fuel delivery?

http://cafefoundation.org/pdf/ignition1.pdf