Overheating!! - Troubleshooting not going well
 

little background, '72-400 .030, summit 2800 camshaft, 16 heads (9.75:1 CR)
running/breaking in on test stand at 2500 PM, new Champion radiator, electric fan w/ 180 degree T-stat.

fired up great, all vitals OK except for coolant temp rise to 230 within 10 minutes. initial timing at 16 BTC. removed T-stat and replaced it with gutted one and it will run about 15-20 minutes, but temp will climb to 230 fairly quick after warmup. i did remove the milodon aluminum water pump and adjusted the divider clearance to .010 to .015 clearance with no improvement. for reference, all components inside the timing cover are new- divider, sleeves, seals, etc. so i went to the sticky and copied the following and my best diagnosis as to the current conditions. any advice helpful.


;21 Reasons why your engine may run Hot.




*A lean air/Fuel Ratio (Also check fuel pump and Filter) - ELEC PUMP, NEW FILTER
*Too much timing/retarded timin/advanced curve malfunction -VARIED TIMING WITH NO SUCCESS
*Clogged Radiator/Collapsed Hose (restricted water flow) - NEW, NEW
*Clogged Engine (restricted water flow) - NEW REBUILD (CLEANED)
*Stuck Thermostat / Incorrect Thermostat - tested WITH, WITHOUT, AND GUTTED
*Bad Water Pump - NEW AND CLEARANCED
*Incorrect Water Pump Speed (too slow/too fast)- FACTORY PULLEYS

*Radiator Too Thick - SPEC'D FOR ENGINE (NEW) Champion
*Wrong Pressure Cap - 15#
*No Shroud Around Fan. Improper Fan Position Within Shroud. - ELEC FAN W/IN 1" OF RADIATOR, NO DIFF WHEN ADDING HIGH FLOW SHOP FAN
*Bad Fan Design - Stock Factory Type Usually Works Best. - NOT TESTED
*High Volume or High Pressure Oil Pump - NEW MELLING FACTORY SPEC PUMP (GOOD OIL PRESSURE)
*Electric Fan (Pullers/Pushers) Blocking Air Flow - (Puller) ADDING EXCESS AIR MADE NO DIFF
*Too Much Antifreeze - 50/50 BLEND
*Wrong Type Antifreeze - CORRECT
*Flow Test: Begin with cool engine. Remove radiator cap. Start engine. Bring engine up to operating temperature so that the thermostat opens. Increase engine speed to 2000 rpm. If water gushes out of radiator there is a flow restrictionin the system. This must be corrected for proper cooling. - NOT TESTED
*Wrong Spark Plugs (ie. Heat Range) HEAT RANGE "5" AS RECOMMENDED BY BUTLER
*Wrong Gasoline Type (Try 89 or 92 Octane) - 89 CURRENTLY
*Clogged Catalytic Converter. - NA
*Clogged Injector System. - NA
*Exhaust getting into the water due to a cracked head or blown head gasket. - SYSTEM HAS BEEN PRESSURE TESTED

Again, i am running the engine on my test stand with all necessary components connected. can supply pics if necessary.

First I’d verify that your gauge is correct. If it is, the first thing I would be suspicious of is the electric fan. I’ve not had good luck with them in the past.

Good luck!
Murf

I run this radiator in our 68 Firebird. https://www.griffinrad.com/inc_resul...model=Firebird

It has 2 rows for cooling that are 1.25 wide. No issues. Your initial timing is 16 deg. What is your total timing? All in by what rpm? The stock cast water pumps with cast iron impellers in my opinion are hard to beat. Also run the smaller pulley on the water pump. A 160 deg thermostat is fine also if driving in the summer.
Do you have you electric fans turning the proper way? Also, what kinda shield is on the radiator with the fans? Post some pics.

I had similar issues on my test stand. 2500rpm with fake air movement from my test stand electric fan wasn’t enough. 10min was about my limit too. I did my break-in over the course of 3 separate runs after cooling down. I also swapped my regular mechanical fan on it with a temp shroud around it.

I figured that even when the engine is in the car with air being ducted over/under/around the engine the way it was designed, I’d still be looking for trouble sitting still trying to hold 2500 for 30min. After break-in, idling on the stand was not as big deal temp-wise.

X2 above. The electric fan and lack of fan shroud are suspect. I know you’ve tested with a high speed shop fan, but that might not be enough. Also infrared thermometer on temp sender to verify gauge accuracy.

Some say that air pockets in the cooling system can cause overheating. When I’ve have had similar cooling gremlins with new/rebuilt engines they’ve eventually gone away after tinkering with the system and filling/refilling the coolant, which makes me think there may be something to that. Try filling the system with the heater hose (coming out of the head) disconnected, and then reattach the hose once coolant starts coming out of the hole. Also drill a couple of holes in the thermostat (assuming you’ve put it back on). Then when you start it up, turn the heater on full blast, and leave the radiator cap off, adding coolant as necessary. This should get any air out of the system.

The only other big factor that has worked for me in the past has been adjusting the initial timing. I see you’ve already tried that, but you may consider further investigation down that road, as it seems to have the most significant effect on overheating when everything else is ship shape.

Do the electric fans have a shroud covering the rest of the radiator? I had the cold case fans and my GTO and it kept overheating. Took the shroud off and it helped dramatically. I went back to a clutch fan.

The shroud was blocking the air flow

This ^ a lot of the shrouds I’ve seen are too shallow & flat. Look like a baking sheet with a hole in the center. I don’t think the air can flow through & kinda stacks up in there.

Murf

Essentially the only airflow I was getting was two 14” circles- the rest was useless.

thanks for all replies. i did have reservations about the cooling fan/s and running a constant 25K RPM, but this isn't my first rebuild or first Pontiac rebuild (lotta Chevrolets) and have never had this issue before. i'm gonna install a factory shroud and mechanical fan next. the system has been burped of air and. new Moroso full flow T-stat is on the way.

Any other input is greatly appreciated.

Have you verified your timing marks are accurate? If the balancer has slipped, or is marked incorrectly, your timing may not be what you think it is. Retarded timing will make one run hot.

I’d bet dollars to donuts your heating issue will suddenly go away.

Also 230 isn’t really “overheating” especially if your running a 15 lb or so cap.

Murf

Pontiac engines don't put enough cooling to the rear or middle if the blocks. Running fuel with Alcohol can make it even hotter.
The engineers designing the shroud and fan set up knew what they were doing.
The day I see a flat front air intake on a jet engine, I will use one. Seems air and water do NOT like a "wall" or sharp corners to go around. Funny how basic aerodynamics has been Ignored on cars, but Not on jets..or boats..

Want to have even heat through your block with no hot spots? Want the engine to run at the temp your t stat decides? Read the thread below on this page about running cooler started by Steve Barcak. There are pics and explanations.

Many good points here. But, I'm not sure how you can regulate the coolant flow with no thermostat. Even a 180 with a burp hole should work. I missed it if you mentioned it, but someone else did. A good fan in front blowing hard helps. I agree you have to verify temp with a temp gun.

Don't pull your thermostat. Hell, if you're past the thermostat set temp, you essentially don't have a thermostat, anymore, anyway since it's fully open and will stay that way if you're overheating.

Running at 2500 sitting still will require a lot of air movement to mimic highway ram air. With stock gearing and trans, that's around 60 MPH. One good electric fan I've heard positive feedback on is the Flex-A-Lite #295 (116524) with dual 13.5" fans. It pulls 4600 CFM of air, but more importantly the shroud for each of the fans is slightly conical like what is seen on most modern car fan shrouds, and so it's not perfectly flat up against the radiator core like the terrible Cold Case ones I've heard about.

Sounds like it's not a water flow problem, either. Your pump is clearanced, and a Milodon pump is a good pump.

Ultimately I think this is an air movement issue. Either upgrade to a better e-fan, or use a clutch and proper shroud.

And of course timing. 16 degrees initial should be plenty, though. Are you using vacuum advance to achieve good cruise timing? A V8 will happily cruise at that RPM (2500) from anywhere between 48-55 degrees total with vacuum advance added in.

I would suspect the fan(s). What fan setup do you have?

That #295 fan is hard to beat, as long as you have it properly wired and a good alt (and belt doesn't slip).

Is there a spring in the lower rad hose to prevent from collapsing?


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My guesses are too little airflow, and a tight, fresh engine. Once some time has been put on it, it will loosen up a bit. Less friction, equals less heat.

haven't fired it in a few days...other priorities. as soon as i get enough run time, a full flow t-stat, and try a shroud/mech fan i'll know more. only have about 1 hour run time so far. i have an old crap quadra-jet on it now so that may be an issue too. will get a holley sniper efi when installed. i am also doing the rear heater hose Tee mod and a manual ball valve to regulate flow through the heater core based on Youtube's "Fast Monty's" testing results.

use a lazer thermometer and check the temp going out of the radiator and also going into the radiator.Should be a 30 degree drop.Tom

What fan(s) are you running?


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You list the first troubleshooting item as:

*A lean air/Fuel Ratio (Also check fuel pump and Filter) - ELEC PUMP, NEW FILTER

But do not say if you've verified the AFR. At the least, what do the plugs look like?

Also a 204 @ 0.050" cam with 9.75:1?? That is a cam I'd consider if the CR were 7.75:1.


You might also want to cut open the oil filter, and make sure it isn't full of bearing pieces.

test stand has 1-16" electric fan w/o a shroud, and a hi flow squirrel cage shop fan (all run time is on my engine test stand)i cant figure out out to attach a pic...says wrong format so working on that. i will check for the 30 degree drop as a measure of cooling....Thanks TOM S for the tip

-will check plugs
-CR based on table with stats on butler site with 16 heads, -6cc heads, & .030 bore
-why do you suspect i may find material in oil. all clearances and specs were well within tolerances. oil pressure good, and engine is not real stiff (tight). i did buy a spare oil filter to check and will to verify. i take all reasonable input as credible, thanks.

i've been going on wisdom shared to me by my dad 40 yrs ago that If your car is overheating in park then you need a bigger fan, if it overheats on the freeway then you need a bigger radiator. i am going to install a factory fan and shroud first, and after that i guess a bigger radiator. i bought the champion a year ago (same as in the car now with a stock 455) for the test stand so what should i try next...rodney red, griffin, ?, they get real pricey sometimes.

FYI,in my 69 firebird with a factory 350 auto radiator and V8 pontiac engines from 366 to 455 and everything in between it has never over heated.Factory flex fan and factory shroud.It has a small fan pulley and std balancer pulley. Tom

A 16" fan is no way enough, probably only is 2-2500 cfm at best. That's your problem. Am very sure of it. (I've tried a lot of fans)

Try this one:

https://www.summitracing.com/parts/der-16927

Or one that is similar that fits over as much of rad core as possible.

Putting a shop fan in front of it helps some, but not enough to make a reasonable drop in temp.


,

Ever see a FLAT surround on a JET engine INTAKE? , or exhaust?
Getting "more fan" can cover more radiator, but NOT all with the FLAT "shroud"
THe HP needed to run those fans is MORE that a stock Clutch fan would use, and that does NOT restrict ANY air.
IT amazes me that Simple Wind dynamics and air movement, and even hydro dynamics cant seem to make to Under the hood of a car in the aftermarket.......
GM engineers DID the Homework. in 1970 Ram air IV cars were tested in the Desert....
If anyone questions GM and fan shrouds just look at a '71 or '72 Grand Prix...
GM put a WIND TUNNEL in that car.....

It's not flat shrouds that are the problem, it's flat shrouds that are too close to the core.

I have that fan on a 535ci with AC and a 495ci (Olds) with AC, both run right at the stat, +5 degrees in extreme conditions.

It also has pressure reliefs to allow more air flow at highway speeds.


.

This. A flat shroud that is too close to the radiator core will only dissipate heat effectively from the area of the core directly behind the opening for the fan itself, while the rest of the radiator core will be poorly exchanged. That's why shrouds are ideally conical in shape. In that case, you'd almost be better off running no shroud.

The whole point of a shroud is to maximize the surface area of the core that is to transfer heat in the presence of a fan that is not able to cover the entire surface of the radiator. The shroud effectively traps the heated air inside of it so that it can be extracted by the fan away from the core, thus dissipating the heat. With a shroud that is too close and is flat, the suction of the fan will not be able to grab all of the heated air from the entirety of the core; while on the other side of the coin, no shroud at all means the fan is grabbing a mixture of ambient air as well as air from the radiator core that contains transferred heat. No shrouds are great for highway travel, not so good for low speeds/idle.

I switched from factory non AC pulleys to AC pulleys and it made a big difference on my car.

If Flat worked, GM would have used it LONG ago. People compensate for the "Flat" by more, or more powerful fans.
Olds never have had a heat issue like Pontiac.
The radiator can never be as efficient where there is a Flat "shroud"is , even if the flat is 2 inches away, Vs the fan area.
When Fan shrouds were developed Gm engineers put like 50 vacuum gauges on their test car, all over the shroud, to get an idea of total area performance.
If Flat worked, and took up less space, they would have used it.
Try to find a flat funnel.
I understand the public has been duped by all this and its so easy to open the catalog and buy new stuff.
Most times the factory set up actually works.

Look at race cars that run on a closed course for more than 13 seconds, you won't see any electric fans on them. I have no idea of why people think electric fans are superior to an engine driven one. They will not ever move the amount of air that an engine driven one will, and the aren't linear with heat production generated by RPM change.

Running a Pontiac on a dirt track will challenge anything you think you know about keeping one cool. I had to do some unorthodox things to keep mine cool, but when I got the system optimized, you would never see 180, no matter how hot, and humid the ambient air was.

Engine driven fan, with a RV style composite fan blades, 2, 3 core radiators back to back. A/C pulleys. As much radiator area as possible, and a fan that will pull as much air as possible through the radiator and shroud system. The composite fan is very light (11 ounces) has a near 90 degree pitch on the blades, so you run direct drive, no clutch. Even at idle it pulls a huge amount of air.

Not having a cooling system that could remove heat as fast as it was generated, cost me a brand new fresh engine. Having to completely rebuild a new engine that ran only 1 race, is a hard way to learn to have a cooling system up to the job. Expensive lessons are the hardest to swallow, but you won't forget it.

:2cents:

Its not that electric fans move more air than big engine driven fans. Typically they dont. However, most people whose classic cars are set up even close to correct only have a problem at idle or stop and go traffic.

At these low RPMs, a good electric fan will still be giving its max air flow where the engine driven fan is limited by the low RPM of the engine. So if someone can get more air flow at the area where their vehicle actually needs it, AND save 10-12 HP by switching to electric. Its an easy choice.

I say this as someone with a clutch fan setup running cool. The pitfalls of the electric fan is that people cheap out on them and get units that arent sufficient at any RPM.

That's the number one reason electric fans get a bad rap.

Number two reason is a toss-up between poor wiring and/or shroud design.

If you don't have a specific reason to switch, then by all means, stick with a mechanical.

I switched for multiple reasons, one being amp load of accessories. Once you go beyond a certain amp load (EFI, electric pump, big stereo, etc), a V belt can't handle the alt load. I've found that right around 150a is the tipping point. Solution: serp belt setup.

Another reason I switched was as mentioned, stop & go/low speed for extended times. I daily drove my car for a long time, in stop & go traffic, with AC running in 100+ degree weather.

With 2 fans, the shroud has less impact, the areas of 'vacuum' overlap, and make up for some of the poor designs. Can't really think of a good way to put that, but there it is.

There are also advantages over mechanical fans when using a PWM controller, you basically only use what you need with those, regardless of RPM or vehicle speed. Can even use them when the engine isn't even running.


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Or shut them down at speed, when/if they're not needed.

I've also run the composite engine driven fans on street cars. You can leave them idle for hours, they won't get hot, and driving 11 ounces of nylon fan, the only energy you use, will be to move air.

There is no free lunch, the amount of electrical energy you use to run the alternator to run the fans is taking power from the engine at idle also. and why do I care how much power I use at idle?

For whatever reason Pontiac engines have always been tough to cool. You can run a SBC with a electric fan and it will never get hot. Try the same thing with a Pontiac, and it will run hot. It just takes a much higher heat transfer of BTUs on a Pontiac.

There are few well engineered electric systems that are going to cool a Pontiac V8. By the time you get a pair of fans and a shroud that will cool one, you're using just as much electrical energy as a light composite engine driven fan, plus the composite fan is $30. They don't make a 19 inch fan, but the 18 inch fans have worked well in the past for me. Space them properly in the shroud, and they'll pull plenty of air at idle. Flex a lite has been making these fans for at least 45 years that I know of, and they work very well.

https://flex-a-lite.com/18-inch-nylon-fan.html

I want to drive the car and look through the windshield while I'm driving, not keep looking at the coolant temp gauge to see if the electric fan is able to keep up with the engine. Even when Pontiac engineers were trying to eek out the last bit of mileage by lightening things on the 301/265 engines, like making the timing chains and gears 2 rows thinner, and running aluminum hoods on the B body cars, they never resorted to running electric fans to save fuel.

My 05 GTO has electric fans, and a large aluminum radiator, but it also has an LS2 aluminum engine, nowhere near as hard to cool as a Stratostreak engine is. If I took a GTO cooling system from a late model GTO, and tried to cool a Stratosteak engine with it, I'm certain that it wouldn't be up to the task, the capacity of the system just isn't there.

If you ever wanted to run a large aluminum radiator and electric fans, the late GTOs have a heck of a system already engineered, but I doubt it would cool one of the dinosaur Pontiac V8s adequately. It does fine on a LS2 with A/C, but I just don't see it working on a 350,400, or a 455.

Someone that is industrious, and has access to used late model GTO parts could prove me wrong, someone should try it. Good science project, and around here there are a lot of late model GTOs being parted out, so parts shouldn't be hard to come by.

Myself, the juice ain't worth the squeeze.

Yup, I shut mine off at 65mph. They are also off under 160 degrees.

.

Mikes Reply:

See this Thread that is going on now!

https://forums.maxperformanceinc.com...50#post6336050

One thing I agree with is that the Fan Blade, on the conventional Factory set-up, should be sticking out a little past the inner Shroud so the tip grabs some air under the hood, I believe this allows the blade to spin better with less resistance?

I use this fan and its the first electric set up I've ever used that actually cycles. It pulls an amazing amount of air. I have it set to go on @ 188* and off @ 180. When it kicks on it drops my temp to 180* within a minute or so. My car can idle with the A/C on indefinitely. With A/C my temp never goes above 192* on a 98* day.

Yeah, it's like 4600cfm, will suck a beer out of your hand if you get too close when it comes on!

They draw 28a each, 56a total, which is a hard hit on the alt/electrical system. Need to run a controller with it.


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On another note, this fan (Flex-A-Lite #295) technically is a replacement fan for a Silverado. I have it in my T/A it seals to the core perfectly. There are no air leaks whatsoever. It's not going to a first gen F, but second gen F and I'm sure it would fit an A body. Besides fit the number one reason I picked this fan was it is the only aftermarket fan with a 4600CFM rating, nothing else comes close.

In my opinion there is no electric fan set up that will pull more air than a mechanical stock set up. BUT, all new cars performance or not have electric fans with no issues. You would be better off with a junkyard electric fan/shroud combo than just about any aftermarket setup. They are just better engineered. My son has an Xtreme blazer with 6.0L and A/C he is using a dual electric fan and shroud out of Dodge Intrepid and he has no cooling issues with or without A/C on.

I agree with both comments: when my fans kicks on if you standing near the grill it it pull your Tee shirt toward the grill.

When it kicks on it is a hard hit to the electrical system. I have separated the two fans by having Fan 1 kick on first then Fan 2 right after. But, when I turn on the A/C its a triple hit actually quadruple, both fans, compressor and blower. I'm working on that issue now.

'78 T/A? Get one of those fancy serpentine belt systems that come with those powermaster 170 amp alternators. That's what I plan to do. 170 amps should be plenty for all that stuff, including EFI if you throw that into the fray, but an alternator with that output is going to need something more reliable to drive it than a V-Belt which is where the serpentine comes in. Oh, and some big chonkin' wiring. LOL

That's a $1500 dollar fix. You could just change the alternator...My alternator puts out 110 amps as it is. It handles the amp draw no problem. Its the initial shock.

https://www.youtube.com/shorts/7YvyMTSFpg4

enough to suck small children off of the sidewalk... ;)

Thinking outside the box here, but what about using something like a .5 farad capacitor like one made for high power amplifiers? Run your fan relay power source off the capacitor and that would absorb the current shock.

If you get too close you can lose ideas...

a simple fan controller will do you pretty good to help manage your turn on loads.

Enjoyed the comedy in recent posts. Problem was def the fan/airflow. I removed 16" electric and mounted a 18" mechanical flex fan, still have the gutted t-stat. Waiting on Moroso full flow, but running (2500 rpm) 30 min at a time the gauge never rises off the needle-stop (100 degrees). After 30 minutes, shut down, gauge will rise to 175-180. Gonna drop in a 160 t-stat and let the fun begin. Gotta get better e-fans for my test stand though (thinking "black-hole" sucking specs :cool:). Thanks for all of your input, all was thought provoking and useful.

Temp always goes up after engine is turned off!Tom