Overheating mystery

[Abomination 0]

So, I have a 1970 mustang vert.  Its a base with a stockish 351w with what sounds like, a mild carb.  I put vintage air on it and sniper efi on it.  Its tuned to be 13.5afr at idle (750rpm). 

So, car started overheating (vegas and A/C, so not unexpected) while idling.  Looking at it I decided to replace my cooling system.  I upgraded to a 4 core aluminum big block radiator with a great shroud and dual spal fans.  I upgraded the water pump to a high flow aluminum pump.

It still overheated.  I did a prestone flush, cleaned out some brown water but no gunk.  Refilled it, still overheated.  Replaced coolant with distilled water and water wetter... still overheats.

I did a block test, no head gasket.  Oil is clean and fresh, no signs of a head gasket.  Took a flir camera to it, no hot spots on engine.  Radiator flows well and I can see it flowing.  Thermostat is new, 190 degress.  Verified working.   Replaced radiator hoses with another flush, no collapsed coolant hoses.  No coolant leaks.

It will still overheat when idling.  At speed it is fine.

I'm at my wits end, hopefully someone has some advice or direction.

[jmlay 80]

I would guess it is an airflow problem. The ac condenser is causing lower airflow and, when the ac is on, additional heat. 
 

What cfm are your fans rated? If you put a sheet of paper on the radiator with the fans on will it be sucked tightly to the radiator?
 

[Abomination 0]

Hmm... well I got this fan and radiator combo.  It says 870 cfm each.  They are hot wired with relays so are getting full power.  Yes with the sheet of paper question, those fans put out some air.

https://www.cjponyparts.com/radiator-4-row-aluminum-polished-24-type-379-big-block-mustang-1967-1970-with-air-conditioning-302-351-1970/p/RADA37/?utm_source=Pony&utm_medium=Email&utm_campaign=OrderConfirmation&lac_guid=737caf85-edf4-ec11-8368-0050568ba4b7

https://www.cjponyparts.com/dual-electric-fans-with-shroud-mustang/p/FAN18/

[rwcstang 201]

When you say overheating, can you describe in more detail?

• is it boiling, spewing out coolant?
• Replaced the Radiator Cap?
• does it over heat with the AC on or Off or all the time at idle?
• have you confirmed what are the actual temps are at idle? 195-220 should be normal operating temperature. fluctuating temp is fine, its going through heat cycles.
• Re-Check Timing? does it detonate, ping?
• you most likely need more CFM to pull-in Air at idle. Are both fans on at the same time or do you have them timed separately?
• have you checked amperage on the fans? if you are riding a stock alternator, it may be the fans are not getting enough Juice to pull the correct amount of CFM.
  • I have the aftermarket Dual Contour fan on my 427w stroker but I use a 140amp 1 wire alternator. maybe Converting your stock alternator to a 3g 140+ amp may help. 

[Mach1 Driver 560]

8 hours ago, Abomination said:

I did a block test, no head gasket.  Oil is clean and fresh, no signs of a head gasket.

Sorry, I'm not following here about the head gasket- could you elaborate please?

I don't see any mention of your timing. Is the Sniper controlling timing or not? I agree with all of rwcstang's comments- what is your actual temperature? Electric fans pull huge amps and require and upgraded alternator. Are you running a serpentine pulley system now? How about some pictures of the radiator/fans/pulleys/shroud so we can get a better idea of your setup?

FYI, according to Marti, some 70s received a 351W two barrel instead of the more common and new 351C.

[jmlay 80]

You should check all of what is mentioned above. 1740 cfm, if that is what is actual being pulled through is definitely not enough air. 

[Abomination 0]

12 hours ago, rwcstang said:

When you say overheating, can you describe in more detail?

• is it boiling, spewing out coolant?
• Replaced the Radiator Cap?
• does it over heat with the AC on or Off or all the time at idle?
• have you confirmed what are the actual temps are at idle? 195-220 should be normal operating temperature. fluctuating temp is fine, its going through heat cycles.
• Re-Check Timing? does it detonate, ping?
• you most likely need more CFM to pull-in Air at idle. Are both fans on at the same time or do you have them timed separately?
• have you checked amperage on the fans? if you are riding a stock alternator, it may be the fans are not getting enough Juice to pull the correct amount of CFM.
  • I have the aftermarket Dual Contour fan on my 427w stroker but I use a 140amp 1 wire alternator. maybe Converting your stock alternator to a 3g 140+ amp may help. 

Sure.  It isn't boiling, the temp gauge has gotten to 235 before I shut it down.  Verified with manual gauge and the coolant temp sensor on the fast efi, both match.

I have replaced the radiator cap.  I also put a vacuum pump on the coolant system incase there was a bubble

It overheats all the time, but quicker with the ac on.  Only at idle

At idle it continually creeps up, never really hits a limit

Its electronic timing, and yes it is verified.  It doesn't detonate/ping that I can hear.  I did hear some backfiring while slowing down under load yesterday

I have both fans on at the same time

 

I havent thought of the alternator, it is putting out 14 volts but didn't check amps.  Ill look into it, thanks

[Abomination 0]

7 hours ago, Mach1 Driver said:

Sorry, I'm not following here about the head gasket- could you elaborate please?

I don't see any mention of your timing. Is the Sniper controlling timing or not? I agree with all of rwcstang's comments- what is your actual temperature? Electric fans pull huge amps and require and upgraded alternator. Are you running a serpentine pulley system now? How about some pictures of the radiator/fans/pulleys/shroud so we can get a better idea of your setup?

FYI, according to Marti, some 70s received a 351W two barrel instead of the more common and new 351C.

Head gaskets being blown can cause overheating, I checked it multiple ways and that is not it in this case.

Timing is electronically controlled by the sniper.  Actual temps are the same as the gauge as verfied by a flir temp gauge, mechanical gauge and cheap ir laser.

Ill take some pictures today, thanks

 

edit: just bought a new 140 amp alternator to try as well

[Abomination 0]

37 minutes ago, jmlay said:

You should check all of what is mentioned above. 1740 cfm, if that is what is actual being pulled through is definitely not enough air. 

I just bought two 2400 cfm fans based on that conversation, ill update when they are installed.  I'm also doing a heavy coolant flush right now.

[Abomination 0]

Here are some photos of the cooling system.  I took a picture of the gap between the radiator and the radiator support, do you think that 1" gap can be causing an issue?  Maybe I should try and seal it with a rubber seal of some sort?

[rwcstang 201]

no, I don't think that would be a problem, unless you had a mechanical fan with shroud.

I also see you have a grill cover to help redirect air to the radiator which helps a ton!

I have a Dual Contour Fan with out AC setup but the fitment is some what close to yours. it could be either Alternator not producing enough amps for your e-fans or could be your e-fans are fubar and not pulling enough.

most cars that are fully loaded with modern electronics, including Dual E-fans and AC will use 140-200 amp alternators. Im not sure what brand fan controller/relay you are using, did you configure the fans to turn at at a certain temp? if you didnt do that, it will use the default setup.

I have the Dakota Digital Fan controller and relay kit and I can set temps via phone. My single fan will turn on at 195 and turn off at 185, second fan will turn on at 210, off at 200 and fans will shutdown when Im going 50 mph to let air through the fans.

 

 

[Abomination 0]

3 minutes ago, rwcstang said:

no, I don't think that would be a problem, unless you had a mechanical fan with shroud.

I also see you have a grill cover to help redirect air to the radiator which helps a ton!

I have a Dual Contour Fan with out AC setup but the fitment is some what close to yours. it could be either Alternator not producing enough amps for your e-fans or could be your e-fans are fubar and not pulling enough.

most cars that are fully loaded with modern electronics, including Dual E-fans and AC will use 140-200 amp alternators. Im not sure what brand fan controller/relay you are using, did you configure the fans to turn at at a certain temp? if you didnt do that, it will use the default setup.

I have the Dakota Digital Fan controller and relay kit and I can set temps via phone. My single fan will turn on at 195 and turn off at 185, second fan will turn on at 210, off at 200 and fans will shutdown when Im going 50 mph to let air through the fans.

 

 

I just bought a 140 amp and new fans, when they get here I will try that.  It kicks on the fans at 190, same as the thermostat, kicks.  Both fans are on the same circut.

[Mach1 Driver 560]

You've covered most of the bases here so I have to ask a stupid question- are your fans pushing instead of pulling?

[Abomination 0]

1 hour ago, Mach1 Driver said:

You've covered most of the bases here so I have to ask a stupid question- are your fans pushing instead of pulling?

I wish that was the issue, but no they are going in the right direction.  I think I might be onto something with the alternator, at idle it is showing 12v, so new fans and alternator and we shall see.

[RogerC 136]

Can you post a shot of the engine from the front? That looks like a 351C valve cover in the 1st pic. If it is a 351C and you put a thermostat in it for a 351W, that's your problem.

[Abomination 0]

35 minutes ago, RogerC said:

Can you post a shot of the engine from the front? That looks like a 351C valve cover in the 1st pic. If it is a 351C and you put a thermostat in it for a 351W, that's your problem.

Sure, hmm there are 4 bolts on the bottom of the valve cover.  That means Cleveland right?

[RogerC 136]

Yup, that's a cleveland. Thermostat in the block not on the intake.

[jmlay 80]

Since it is cooling while driving I would not expect the incorrect thermostat or missing brass insert. If the incorrect thermostat or the brass insert are missing I would expect it to overheat parked, moving slowly and more than likely at speed down the road, especially where he is. Why? Because, hot water is allowed to circulate in the block with limited return to the radiator.

[Abomination 0]

Ok Ill check.  Should I get a cleveland thermostat or use one of the pantera inserts if it turns out to be an issue>

[jmlay 80]

As long as you have the correct thermostat and the correct brass insert I see no reason to switch to a standard thermostat and “pantera restrictor”.  No need changing parts to change parts. In my opinion there is not enough airflow. Correct this first and reevaluate.

Some explanation of the Cleveland thermostat and operation.

https://www.coolcatcorp.com/thermostats/Ford.html

[det0326 179]

On 9/23/2023 at 8:24 PM, RogerC said:

Can you post a shot of the engine from the front? That looks like a 351C valve cover in the 1st pic. If it is a 351C and you put a thermostat in it for a 351W, that's your problem.

good eye there Roger. I was thinking the same thing before any pics and the site crashed again but I went back to his first post and he stated that it was a 351W. After seeing that I never posted anything. 

[BobW70Mach1 28]

What a great response on this thread.  I chased overheating issues with my Cleveland for a long time after my rebuild.  After switching fans and radiators multiple times I finally figured out it was the thermostat.  Duh!  Such an easy fix.  I remember going to the parts store during my rebuild and specifically asking for a Cleveland thermostat because I knew they were different.   I was too inexperienced to realize they gave me a Windsor thermostat.    They insisted repeatedly it was the right one.  I asked “Are you sure?”  “Yes.  We are sure.”

Also there is so much misinformation out there.  A lot of “know it all” people even say to remove the brass ring to solve overheating issues.