Age old overheat with a twist - Vintage Mustang Forums
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post #1 of 50 (permalink) Old 09-05-2019, 09:25 PM Thread Starter
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Age old overheat with a twist

New guy here looking for some advice.
Have fixed same problem for other guys but cant fix my own. Built my car from just a body so I have no BEFORE reference. Just mix of performance parts.
I have a efi stroker 331 (crate motor) with vintage air ac. From the time i got this car on the road 8 years ago it will overheat in traffic ONLY at idle with AC on and over 95 degrees.
Can be 100 degrees and ac off its fine. Can start moving at any point and temp will go down to normal until stopped again in traffic. Driving down the road is between 180 to 190.
Can ride it hard and temp will stay below 190.
After 225 degrees is when i shut the air off and it will cool its self right back down.
Now the history- started out with milodon high flow pump and high flow thermo stat. Electric fan and shroud. Aluminum 24 in. Radiator . Swapped 180 thermo about 5 times, Then went to Flex a lite Mechanical fans working my way thru 3 different versions up to 7 blade ( no clutch)
Then changed to new aluminum 2 core 1 in. Tube radiator and changed water pump to flowcooler style. Still no change. Replaced all hoses again (bottom hose is not collapsing) changed pulley sizes, even readjusted clearance between condenser and radiator. Had ac pressures checked. Started my way thru 3 electric fans 2400 cfm to 3000 and now running contour fan swap. No change. Changed idle mixture up and down, changed timing, flushed block and radiator numerous times never saw anything come out. Checked gauge multiple times. (Have 2 temp gauges- 1 dash 1 on efi. Even changed oil pump to make sure i was oiling properly.
Appeartly there is something i missed cause it still doing it. Any suggestions?
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post #2 of 50 (permalink) Old 09-05-2019, 09:56 PM
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Sounds like you've spent a ton of money trying to solve this problem! I would look into a timing issue at idle and I'm sure others that know about this issue will respond. I've spent a ton of money myself to solve weird issues on my Mustang. Just not your issue. You seem to be determined to fix it!

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post #3 of 50 (permalink) Old 09-05-2019, 10:15 PM
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I don't see a 7-blade thermal clutch fan on your list. If that can cool a CobraJet with AC, it should do for you.

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post #4 of 50 (permalink) Old 09-06-2019, 07:04 AM
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As always, some pictures may help in diagnosing the problem.

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post #5 of 50 (permalink) Old 09-06-2019, 07:28 AM
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Describe how the electric fan operates. What is the trip temperature? Have you verified it? Sitting idling in the driveway and up to temp, fan on or off? Puller or Pusher fan and is the orientation correct?

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post #6 of 50 (permalink) Old 09-06-2019, 09:32 AM
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225230* is hot-ish but not yet overheating.
Try a 195* thermostat next.
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post #7 of 50 (permalink) Old 09-06-2019, 10:04 AM
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The cheapest solution is probably moving... ;o)



When it overheats, if you rev the motor to say 2k while at a standstill, does it drop the temp? I'm thinking you may have a ratio issue with your pulleys. See what the lowest RPM that keeps it cool is, if it works then do the math to get the right pulley ratio.


In a proper situation, a 195 thermostat temp will do nothing to help this situation - open is open after the temp has been reached...

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post #8 of 50 (permalink) Old 09-06-2019, 12:31 PM
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...or turn the heater on when the needle climbs.

I have seen the higher * t-stats help with the small rads until it gets into a runaway situation. A low temp becomes the same as having none at all although with a good 24" rad I think it should never reach runaway temps without a bigger problem.
Good idea about raising the RPMs as it get warmer but I dont know if it helps by flowing more water or moving more air. With it only happening at idle on a hot day with the AC on its minor and might not really be a problem outside the mind at all. GM seems better at putting actual numbers on the gauges, a C3 I had 210 was the middle, yellow warning about 230+ and red wasn't until nearly 250*. That has always stuck with me and confirming on other cars with an extra gauge poor running doesn't happen until about 250, iron is tough and can generally handle it, then after that detonation which I think is the real killer from overheating. Lucky Ive never had an aluminium engine or heads overheat I guess.

The simplified logic I picture it as time in the rad helps lower temps. Without being able to quote numbers or % of * drops from top to bottom of rad I just see it as this: With a low temp t-stat the coolant leaves the engine sooner then through the rad, back into the engine quicker, then a shorter time back up to temp then back into rad through the rad quicker to engine and back up to t-stat temp quicker. So with a higher *stat water leaves engine into rad and brings in water that is cool enough(ideally) to not be at temp before the top of the engine and restrict at the stat which slows flow so water is trapped in rad longer so its drops * more. then when it opens again that cooler water takes longer to reach temp so the stat closes thus letting the next cycle of water stay in the rad longer again so that the trip back up to full open temp takes longer once again.
Thats my story and Im sticking to it

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post #9 of 50 (permalink) Old 09-06-2019, 01:28 PM Thread Starter
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Motor is a 87 5.0 block stroke out to 331 using standard rotation pump (both times) you can see flow across top of radiator with cap off,looks normal like any other I've seen.I have tried different timing settings at idle and afr and tested. It either idle bad or made no difference. Motor seems very happy at 15 base.
Have tried puller electric fan(s). All have been full shroud. Mechanical from flexalite that they said was for idling to pull more air.Currently contour set up. Wired right,pulls strong currently with a cooling components fan controller ss-2. Comes on 185ish for low and then high at 195 ish. With ac on fan comes on high anyway.
Doesn't matter if you try to raise rpm while at idle doesn't cool until moving or ac off.
Currently 1 to 1 ratio on pulleys-cvf beast serpentine kit.
Before was overdriven by 1.2 with march pulleys (i believe).
Even using trans cooler to keep out of radiator. Also went as far as lining front of grill/support to only allow air to go thru radiator ( boy, do i catch some air at 80mph)
Used all the brands of local auto parts water wetter additives. Currently 65ish/35ish water/antifreeze mix.
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post #10 of 50 (permalink) Old 09-06-2019, 01:31 PM Thread Starter
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When it happens it slowly gets to 210 increasing more rapidly to 220 and then like its counting up by 2 from there and then i chicken out and turn off ac. Highest ive seen was 235 and motor started running bad (open air filter to engine bay)
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post #11 of 50 (permalink) Old 09-06-2019, 01:35 PM
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If the overheating only occurs at idle with the a/c on I can think of only two reasons (there are probably more).
First, turning the a/c on is somehow messing with the electric fan, but that doesn't apply as you have the same problem with a mechanical fan.
Second, the a/c is somehow messing with the timing. Check your timing at idle with the a/c on and off and see if there is a change.

Good luck. And keep us informed.
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post #12 of 50 (permalink) Old 09-06-2019, 01:41 PM
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Quote:
Originally Posted by dobrostang View Post
In a proper situation, a 195 thermostat temp will do nothing to help this situation - open is open after the temp has been reached...
His point remains the same. A 220*-230 isnít over heating but a 235 would be too hot. This is common in nearly every ďover heatingĒ thread where the running temp is under spec (which is where the proper thermostat comes into play) and the high temp is still within spec though at the higher end. A point that is missed on these type threads is if the drivability is impacted. In many cases there is no impact in drivability (though in this case it appears there is under some conditions) itís only the driver being concerned with thinking the vehicle is out of range when it isnít.

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post #13 of 50 (permalink) Old 09-06-2019, 01:56 PM Thread Starter
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Have tried checking timing with ac on/off stays the same at 15 base.
I say highest ive seen is 235 because that where i chicken out not that thats where it stops. It will keep going.
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post #14 of 50 (permalink) Old 09-06-2019, 01:59 PM Thread Starter
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I even tried one of those filters in upper radiator hose (pointing correctly) and never got more than one or two tiny crumbs here and there. Finally just left it out.
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post #15 of 50 (permalink) Old 09-06-2019, 02:39 PM
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Stopping at 235 (or before boil over) good call. Without looking at the specs 15 sounds a bit high as a base. Iím used to using 10 or so (0 on my smogger 67) but I donít have your engine. Are you checking with the distributor vacuum line disconnected?

Iíd have a thermal image shot of the engine to look for hot spots since it looks like youíve tried quite a lot. That may narrow it down.
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