New Overheating Issue After Updates

[Coultl]

I've read through threads on engine temp and overheating and I'm still stumped. I did a good bit of work on the car and finally got out for a drive today. The temp used to run right above the first white hash mark and now it gets very close to to the second hash mark. If I let it idle it keeps getting warmer. I shut it off before it hit the second hash mark. 250F is too hot in my book!

- I'm in Boulder and it's not hot here right now. Was 80F today but it still ran hot tonight when it was 60F.

- Here's what I changed on the engine: new oil + filter, 20W-50, Mahle filter, all new ignition components, rebuilt alternator, new fan housing (OEM), painted fan and housing, new fan belt.

- The fan belt is quite tight so I don't think slipping is the issue. I can turn the engine over from the fan pulley but the belt does slip when a cylinder hits compression. I can get through it if I move slowly.

- I know the oil thermostat is opening as the oil lines and front cooler get very hot. The lines are crushed a little. Not helping I know, but it wasn't an issue before.

- I properly oriented the air guide on the back of the alternator. I also double checked to make sure there was no debris or leftover shop towels stuck on the top side of the cylinders. Super clean in there.

- Is there a way of telling if the thermostat for the cooler on the back of the engine is working?

- I have the heater ducting on the top side of the engine removed as I am going to backdate the heater piping. I kept the pipe connected to the fan shroud and blocked off the opening so that none of the cooling air could escape. Seems like this should help cooling if anything!

I'm stumped! It's really not a very complicated cooling system and I don't see what else could cause this. All ideas appreciated!

[911obgyn]

What year car? Is the timing adjusted?

[EC900]

The engine fan does the bulk if not 99% of the cooling, I don’t expect much help from the little auxiliary fan other than push air as intended for heat exchanger cabin heat. Good you checked no critters built a nest in the cavity which is known to happen.

Idling at 80° outdoor temperatures will increase engine oil temps, doesn’t matter high noon, slow traffic, rr crossing or driveway. Driving around town, occasional traffic lights fluctuating high temps is normal, I don’t obsess over this during hot summers. 250° is high but expected with prolonged idling, nobody here has every been to the 300°-340° mark (at idle) to tell what happened next. Some rebuilders I’ve seen on YT always demonstrate their builds with a box fan helping out with the cooling.

City driving bites, I can fluctuate 20-40° (180-220°). What are your highway temps?
Also there’s a good chance the dash gauge is not that accurate anyway.

Handheld Infrared temp gun is good to have in the toolkit. But the baseline needs to be established and everyone I seen has different locations to test and temps vary to figure out what is a normal range. Wouldn’t hurt to start write some temp figures down and check a few points like the oil cooler, lines and monitor.

Altitude timing is a consideration as stated.

[john walker's workshop]

If you block off the air flow to the exchangers, they run hotter due to no cooling air. There you have it.

[Nditiz1]

Can you provide more detail on the hash marks as the differ from year to year. I would start with checking the gauge and temp sensor as well as an infrared gun on the oil lines to the cooler.

82 stock engine with SSi in the middle of summer 95+ days 210 is the max I hit unless hitting it hard on curves living between 5-7k, then maybe 220.

The maintenance you did shouldn't have the ill affect on your engine, something is not adding up.

[Discseven]

Originally Posted by john walker's workshop

If you block off the air flow to the exchangers, they run hotter due to no coolong air. There you have it.

[Schulisco]

What exact car and engine code?
I had the same issue (overheating way beyond known temperatures) due to wrong ignition timing. Dizzy was bad and won't adjust ignition timing any more. This leads to way too late ignition while cruising and acceleratong and this causes very high engine temperatures. Way more than expected. Also check if your car is a CIS US model if both vacuum dizzy lines if are attached to the right throttle body output and not crossed...if so this would also cause similar symptoms...

Thomas

[EC900]

Originally Posted by john walker's workshop

If you block off the air flow to the exchangers, they run hotter due to no coolong air. There you have it.

That’s interesting John, Thanks for the tip.

I noticed and overlooked in my case (not the OP) that my alum-paper flex hoses were a bit tattered or broken leading into the top of the HE’s. Makes sense with the heat flaps closed (to the cabin) that the air dump to the ground isn’t at full capacity and with reduced pressure thereby spreading a bit more engine heat within the engine compartment with a possibility of recirculating it back into the engine fan. Guess the same could apply to cracked housings or lack of band clamps.

[pmax]

Originally Posted by Coultl

- I'm in Boulder and it's not hot here right now. Was 80F today but it still ran hot tonight when it was 60F.

A 20F change in ambient making no difference is concerning.

- Here's what I changed on the engine: new oil + filter, 20W-50, Mahle filter, all new ignition components, rebuilt alternator, new fan housing (OEM), painted fan and housing, new fan belt.

What kind ?

- The fan belt is quite tight so I don't think slipping is the issue. I can turn the engine over from the fan pulley but the belt does slip when a cylinder hits compression. I can get through it if I move slowly.

Your fan belt's fine otherwise you'll hear it.

- I have the heater ducting on the top side of the engine removed as I am going to backdate the heater piping. I kept the pipe connected to the fan shroud and blocked off the opening so that none of the cooling air could escape. Seems like this should help cooling if anything!

Post pics of that setup. I would agree the airflow volume remains largely unchanged whether directed to a blocked off HE or at the opening.

[fanaudical]

I'm mostly with John on this one; blocking off air to the heat exchangers does increase engine temp.

One other potential item: Do you have engine temp measurements from before and after other than your on-board temperature gauge? Maybe with a hand-held IR sensor? Reason I ask is is that replacing the alternator means breaking a ground path somewhere, and sometimes that affects how the gauges read. It could be it's not all that different - it just indicates it is...

[Coultl]

Appreciate all the input! A few notes:

- The oil is VR1 20w-50
- It's an 84 so the second hash on the temp gauge equates to 248F
- I used in IR thermometer to check the temp of the front oil cooler and it was ~225F. Makes sense to me that it could be cooler than the head temp by a good bit. That made me think my temp gauge was probably accurate. BUT, I really don't know the relationship between head temp and oil temp at the front cooler.
- Bends my brain to think that blocking flow to the HEs would heat the engine but it's not like I really understand this engine...so maybe!? Insulated exhaust manifold are common now, but that's on water cooled engines.

Here's the kicker. I drove it all day today and it was back to the proper temp range. The weather was the same as yesterday but today the gauge only peaked at a little bit above the first hash mark...exactly as it had before. Drove it all day. No temp excursions.

I have two theories:
- The gauge/sensor are on the way out and giving inconsistent readings.
- The thermostat for the oil cooler on the engine was stuck yesterday and after fully cooling down it freed up.

Not too pleased with those theories, but that's all I can come up with. More than anything else, sometimes I need to chill and give my 40 year old Porsche a day to correct itself. I'll report back with new info if it keeps happening!