Stumped - Mustang 5.0 running hot lean

[DirtDonk]

How do I pull codes? I don't see any OBD or plug on ECU, motor's from a '91.

Look around along the wiring. There should be a semi-triangular shaped thingy (diagnostic connector) laying around hiding somewhere.
It's where you can run some tests with procedures I forget, but that are listed around, and that these guys can tell you too I bet.

I'd rather not keep throwing parts at it, but have kind'a reached the end of the rope with diagnostic capabilities. I have already spent thousands of dollars (literally) on "professional" mechanics and the problem is still there.

How long has it been happening, and when/where did it start? You said it rand great for awhile, but there are still possibilities. Even a BAP sensor might mess with things, but let's see what the KOEO and all those other "K" words show. That's "key off, engine on" and "key on, engine off" or something like that. Watch for the check engine light's blinking patterns.
You do have a check engine light?

Lower radiator hose???
We replaced all the hoses and had the whole cooling system overhauled about a month ago.

Not really a guarantee unfortunately. Especially these days, though the hoses are not as bad off as other parts seem to be.
But basically "new" does not mean better. Or even good! One way to tell would be to squeeze the hose yourself and see if it's got the reinforcing spring inside. If not, squeeze and feel how soft and easy to compress it is. If it's really easy, especially when warm, then it's very possible to get sucked up and reduce flow.
One of the better ways to see this would be a GoPro or similar setup aimed at the hose and see what happens on the highway.
Heck, even a cell phone taped in the right place would do it!

I don't have an overflow bottle currently installed, but I don't see any coolant coming from the overflow hose.

Hmm, first of all, overflow bottles are good things. So if you get the chance put one in.
But that won't cure a cooling issue, just a coolant loss issue.
And you say you're not losing coolant? Kind of hard to believe at 240 degrees! Heck, most of ours will spit fluid out of the hose at 180 if it's full enough.
What thermostat rating are you using, and what pressure cap are you using?
Again, won't make the engine run cooler. Just curious how you can get so hot and not lose coolant. Making me again ask if you've verified temperature is correct on the gauge.

Paul

 

[Broncobowsher]

Fan installed backwards? The concave side of the blade needs to be on the engine side.
If it is flipped it will move a little air a block a lot.

 

[toddz69]

• Could absolutely be a vacuum issue, which FB mustang motors are notorious for. Especially if the distributor is vacuum advance (idk if it is).

Just to clear up one small item for you, this engine does not use a vacuum advance distributor. As Paul noted, these engines have a TFI (thick film ignition) module on the side of the distributor. Timing is controlled electronically.

Todd Z.

 

[Broncobowsher]

What happens if you just rev the engine to highway speeds and hold it there for a minute or two, where you would normally see it start running hot?

Just because parts are now does not mean they are any good.

 

[AGGRV8D]

Just to clear up one small item for you, this engine does not use a vacuum advance distributor. As Paul noted, these engines have a TFI (thick film ignition) module on the side of the distributor. Timing is controlled electronically.

Todd Z.

Correct, it’s an electronic distributor.

 

[AGGRV8D]

See response below:

I’ve inserted answers, hopefully they show up.

Look around along the wiring. There should be a semi-triangular shaped thingy (diagnostic connector) laying around hiding somewhere.
It's where you can run some tests with procedures I forget, but that are listed around, and that these guys can tell you too I bet.

Pulled ECU and harness, wasn’t under dash but just found it under hood. But don’t have the scanner to check it. Going to make some calls.

How long has it been happening, and when/where did it start? You said it rand great for awhile, but there are still possibilities. Even a BAP sensor might mess with things, but let's see what the KOEO and all those other "K" words show. That's "key off, engine on" and "key on, engine off" or something like that. Watch for the check engine light's blinking patterns.
You do have a check engine light?

It ran fine for 10+ yrs between P.O. and myself as a wknd warrior. Parked it about a year ago because this issue came up out of the blue and i didn’t have the cash to fix it at the time. Thought it might be head gasket then but compression tested within range on all cylinders. Based on that, decided to try to diagnose and fix issue rather than go w/ new engine. Spent the past month and a half (and thousands of dollars) trying to fix it. No check engine light, no inlet or OBD to plug into on ECU.


Not really a guarantee unfortunately. Especially these days, though the hoses are not as bad off as other parts seem to be.
But basically "new" does not mean better. Or even good! One way to tell would be to squeeze the hose yourself and see if it's got the reinforcing spring inside. If not, squeeze and feel how soft and easy to compress it is. If it's really easy, especially when warm, then it's very possible to get sucked up and reduce flow.
One of the better ways to see this would be a GoPro or similar setup aimed at the hose and see what happens on the highway.
Heck, even a cell phone taped in the right place would do it!

Confirmed lower hose is not compressing. New hoses are firm, good routing and good quality hoses (rubber, not silicon).

Hmm, first of all, overflow bottles are good things. So if you get the chance put one in.

Yes, it’s on the list just been busy dealing with bigger issues first.

But that won't cure a cooling issue, just a coolant loss issue.
And you say you're not losing coolant? Kind of hard to believe at 240 degrees! Heck, most of ours will spit fluid out of the hose at 180 if it's full enough.
What thermostat rating are you using, and what pressure cap are you using?
Again, won't make the engine run cooler. Just curious how you can get so hot and not lose coolant. Making me again ask if you've verified temperature is correct on the gauge.

Yes, confirmed auto meter gauge is accurate. Lost some coolant, but not much.

Paul

 

[AGGRV8D]

Yes, tried to get it to overheat stationary and couldn’t, even on 100 plus degree day.it only overheats under load. Got it to get hot (up to 205-210 from 185)but not overheat today at load speed on a steep hill, so it’s being caused under load.

Thermostat is 180 degree and yes, we tried the small bleed hole trick for air bubbles.

What happens if you just rev the engine to highway speeds and hold it there for a minute or two, where you would normally see it start running hot?

Just because parts are now does not mean they are any good.

 

[AGGRV8D]

Fan is installed correct and working great.

I am 99% sure this is NOT a cooling issue, the cooling system cools
Car very rapidly as soon as it is no longer under load. And it runs cool on surface streets in stop & go traffic. Only overheats under load (hwy speed and steep incline), I can rev it up to 3-4K + rpms and hold it for several minutes without temp climbing.

Latest theory, blocked port in one of the heads.

Fan installed backwards? The concave side of the blade needs to be on the engine side.
If it is flipped it will move a little air a block a lot.

 

[AGGRV8D]

Latest theory, blocked port on Heads.

 

[Broncobowsher]

I am ruling out tune as the issue. It may be an issue, but not the cause of this. The rate that it heats up is way too quick. Lean/timing off can be hotter, but not to the degree that described. You might get some thermal creep in a couple miles, not a sky rocket rate of climb. That is the signs of a flow restriction, air or water, something isn't moving enough.

 

[AGGRV8D]

Just wanted to make sure you have the correct rotation water pump on there as I'm sure you know the late model 302's run a reverse rotation for serpentine belt set ups.

Yes, correct rotation. Thanks.

 

[AGGRV8D]

Yes!!!!

Agreed, 100%. Seem to be coming to the consensus that pulling heads for hot tank & valve job should fix the issue or at least shed some
Light on WTF is going on. Thank you.

I am ruling out tune as the issue. It may be an issue, but not the cause of this. The rate that it heats up is way too quick. Lean/timing off can be hotter, but not to the degree that described. You might get some thermal creep in a couple miles, not a sky rocket rate of climb. That is the signs of a flow restriction, air or water, something isn't moving enough.

 

[jw0747]

Thermostat operating correctly? Might consider installing a new one just in case yours isn't opening correctly and going with a higher temp thermostat. Mustang EFI engines mostly work better with a 190-195 degree thermostat.

 

[AGGRV8D]

Thermostat operating correctly? Might consider installing a new one just in case yours isn't opening correctly and going with a higher temp thermostat. Mustang EFI engines mostly work better with a 190-195 degree thermostat.

Way beyond that, but thanks.

 

[Rustytruck]

What are you using for a tranny cooler and is it dumping too much heat into the radiator. I would like to see a picture of your radiator and fan system.

 

[AGGRV8D]

What are you using for a tranny cooler and is it dumping too much heat into the radiator. I would like to see a picture of your radiator and fan system.

It’s NOT a setup issue. I repeat, IT IS NOT A SETUP ISSUE!!!
It ran cool for many years with the current configuration and began overheating suddenly.
It is NOT a cooling system issue. The Cooling System brings the water temp down very rapidly when the car is not under load. I can literally set a brick on the gas pedal in neutral at 3k RPM, go to lunch, come back and it’s still at 185 degrees.
It ONLY overheats under load, and the temp climbs rapidly when it does. So, it gets hot 1) at Highway Speeds (55+) and 2) on a steep climb. It will not overheat in stop and go traffic. It will not overheat driving around all day at speeds under 45 mph, but temp does start to climb going up a steep hill.

We are pretty convinced it’s a Head / Valve Issue and are pulling the motor apart. Keep y’all posted. Appreciate the help.

 

[AGGRV8D]

Setup is Be Cool / Griffin / Mishimoto/ Spal ... Trans Cooler, Oil Cooler and PS Cooler all separate and mounted correctly in various locations as to not rob radiator of any airflow. The car has a very robust cooling system which has been recently pressure tested and completely overhauled w/ new high end gaskets, hoses, waterpump thermostats, thermal and remote switches.

 

[AGGRV8D]

What are you using for a tranny cooler and is it dumping too much heat into the radiator. I would like to see a picture of your radiator and fan system.

It’s NOT a setup issue. I repeat, IT IS NOT A SETUP ISSUE!!!
It ran cool for many years with the current configuration and began overheating suddenly.
It is NOT a cooling system issue. The Cooling System brings the water temp down very rapidly when the car is not under load. I can literally set a brick on the gas pedal in neutral at 3k RPM, go to lunch, come back and it’s still at 185 degrees.
It ONLY overheats under load, and the temp climbs rapidly when it does. So, it gets hot 1) at Highway Speeds (55+) and 2) on a steep climb. It will not overheat in stop and go traffic. It will not overheat driving around all day at speeds under 45 mph, but temp does start to climb going up a steep hill.

We are pretty convinced it’s a Head / Valve Issue and are pulling the motor apart. Keep y’all posted. Appreciate the help.

 

[Rustytruck]

If its a head gasket issue i can see that but a coolant check could prove that. If the total timing is out i can see that.,if you have a fuel pressure issue i can see that. At this point i would be checking for a plugged exhaust or plugged cat especially if you have sluggish performance problems. I dont under stand a head or valve problem as those parts dont change in use making an engine run hot.

 

[AGGRV8D]

Okay, so we pulled the motor, tore it down, rebuilt the top end, checked the bottom end and replaced every seal and gasket throughout.
Fired it back up yesterday, runs better than ever... But still overheats and ONLY under load (at 55+ mph and/or going up a steep incline).
There was a little water and rust in the top of cylinder #8, but that could’ve just been from it overheating the day before. Old head gasket looked okay, heads checked out okay but went ahead and had a full valve job done anyway.

At this point I’m stuck thinking it’s either some weird hose that’s collapsing (Smog and Heater Core have been deleted, so there are a few weird hoses) but it’s definitely not the main radiator hoses.
Or
Possibly a transmission issue. I had the Tranny services by a shop a while back who said it’s built 100% right and in great shape, but that wasn’t long before this overheat issue popped up.
Or
Spal Fan - it is definitely working (replaced switches and even tested running it constant on), just someone mentioned that it might not be pulling the volume of air it should. Has anyone experienced degrading performance with the Spal Electric fans before? It’s tough, because I have no basis for comparison. After the thousands of dollars already spent hunting down this issue (and no doubt improving motor reliability and performance along the way) it seems a bit myopic to pause before dropping a few hundred dollars more on a new fan, but I am just getting tired of replacing stuff that works hoping that it’s the weak link.