The impossible to solve overheating problem

I am about to give up and put the car in long term storage, I have an overheating problem which came out of nowhere and it seems like I cant affect it at all. I only have one more trick up my sleeve. Tomorrow I will be booking the car into a garage that is going to take samples of the coolant and determine if there are high levels of co2 in it (ie. leaking head gasket or a crack in the block/head)

------The engine:------
¤ Motor: Chrysler Smallblock 360ci - 5.9L
¤ Heads: 915J machined to 56.8 CC Std 1.88 / 1.60 valves, compression 9,8:1
¤ Cam: CompCams Xtreme Energy XE262
¤ Carb: Carter ThermoQuad
¤ Intake: Edelbrock aluminiumintake
¤ Ignition: Mallory
¤ Transmission: Torqueflite 727
¤ Exhaust: Doug`s long tube headers, 2.5"system

-----The cooling system:-----
¤ Radiator: Big *** aftermarket aluminum one (think its actually for a 96 ford mustang) so big that I had to widen the frame a little to make it fit
¤ Overflow tank: Nissan s14
¤ Fan: Not sure what size, pretty big anyway

-----The problem:-----
¤ The car overheats while standing still or moving at a constant speed for example 45mph
¤ It takes under 10 minutes of driving at constant 45mph to get to 220 Fahrenheit
¤ If the car stands idling it gets to 220 from a cold engine pretty quickly too
¤ If you keep driving or idling it will just keep rising from 220

-----When the problem started:-----
¤ The car came with the original cooling system (4 years ago now) and would overheat once in a blue moon I dont know why.
¤ I upgraded the cooling system (2 years ago) and it never overheated, well, it did a few times but I had the timing to lean

¤ The car has stood still two years with the engine out while I did suspension upgrades. After putting in all back together the car now has a massive overheating problem. The following was done to the engine when out:
1. Changed some freeze plugs
2. Re tapped the manifold bolt hole which goes into the cooling system (front right farthest from driver)
3. Re built the carburetor (it is tuned well, not running too rich/lean)

-----What I have tried doing already:-----
¤ Run with/without thermostat, have even tried with various restrictions to flow
¤ Checked that the lower radiator hose does not collapse stopping flow
¤ Tried putting ignition to very rich-lean and everywhere inbetween
¤ Checked that the temperature gauge is not off with an I.R thermometer
¤ Tightened all the hose clamps for the cooling system
¤ Taken apart the cooling system checked if hoses were ok
¤ Checked the water pump (it was totally fine)
¤ Checked that the radiator is not clogged
¤ Replaced the cooling system with the original cooling system, radiator etc. (same result)
¤ FYI The engine has been flushed a couple of years ago
¤ Compression tested the engine biggest difference between two was 11.2 Bar and 10.3 Bar



Does anybody have any theories? If there is no co2 in the coolant and if maybe changing spark plugs doesnt make a difference I will be giving up and parking the car for the next few years, which kinda sucks after spending so much time and money.

You said you adjusted the ignition from "very rich to lean" -- that doesn't make sense. The ignition controls advance and retard -- the carburetor controls rich to lean. So what exactly did you adjust?

Both extreme advance and extreme retard conditions can cause overheating, for different reasons to do with poor combustion.

That electric fan is large diameter but it doesn't cover a lot of the radiator (looks like less than 50%). Most set-ups use two slightly smaller fans for a wide radiator like that. Have you tried it with the stock engine-driven fan and no shroud?

Put a mechanical fan and shroud on it.

I’m looking at your pictures, it appears everything is lower than the top hose. It even appears the hose to the surge tank is below that upper hose in height. If that’s the case my suspect would be that you have air trapped in the system and it has no way to burp. Again just by looking at pictures.

2 words: Fan shroud.
really, try it !

you can get another water neck that has a filler cap on top to dismiss the air pocket theory.

Check for a worn out timing chain, could cause cam and ignition to run retarded, causing an overheating problem. Easy to check, with distributor cap off, put a socket on the crankshaft bolt, rotate it around to "0" timing mark. Watch or have helper watch distributor rotor as you rotate crankshaft back, stop when it (the rotor) just starts to move, how many degrees did crankshaft move before rotor moved, the fewer, the better.

That electric fan looks like a cheap POS wal mart fan........no offense it really does look bad. You need about 4000 CFM of air flow to cool a high performance V8. BUT that still doesn't explain your highway over heating......unless it gets hot first and then never can cool off. I would start with the fan and add a shroud first. The mechanical fan might be a good idea. And if you do that, I would go with the Mopar Performance viscous fan package with a shroud. Lastly, all radiators AINT on the same level by a LONG SHOT. Did you get one of those Ebay chinkesium specials? Was it a chinkesium special from somewhere else? Those are hit and miss at best. Some cool great. Some won't cool from **** to shinola. One word on radiators. Griffin. If it runs hot with an appropriately sized Griffin in it, rest assured, you got another problem.

First off...use your IR temp sensor to check radiator temp at the inlet then at the outlet. You should have a 20 degree drop (more or less). This will tell you if the radiator is working as it should. Next, it looks like your fan is not large enough to pull sufficient air through the radiator to cool enough. I used one of these dual fans (2011 Malibu) when i had an overheating problem that I couldn't solve:



Next you have to make sure that you cover/close every place that air might bypass the radiator, by that I mean all around the radiator and top and bottom. Also you'll need the radiator support to hood seal to keep engine heat from recirculating to the front of the radiator.
More later.........
treblig

mvh said:

You said you adjusted the ignition from "very rich to lean" -- that doesn't make sense. The ignition controls advance and retard -- the carburetor controls rich to lean. So what exactly did you adjust?

Both extreme advance and extreme retard conditions can cause overheating, for different reasons to do with poor combustion.

That electric fan is large diameter but it doesn't cover a lot of the radiator (looks like less than 50%). Most set-ups use two slightly smaller fans for a wide radiator like that. Have you tried it with the stock engine-driven fan and no shroud?

Click to expand...

Does the timing not affect the O2 in the exhaust at all? I.e rich/lean?
Anyway, I adjusted the advance and retard to pretty extreme in either direction just to see that my timing mark wasnt off or something but it made no difference so I set the timing to where the engine runs best. The carb is adjusted correctly with respect to rich lean.
The car came with an engine driven fan without a shrowd which I have tried since this problem started again yes. Thing is both set ups have worked old and new.

Dubob said:

I’m looking at your pictures, it appears everything is lower than the top hose. It even appears the hose to the surge tank is below that upper hose in height. If that’s the case my suspect would be that you have air trapped in the system and it has no way to burp. Again just by looking at pictures.

Click to expand...

The highest point is the surge tank, then the upper rad hose, then the rad, then the engine. So when filling the system I fill through the upper rad hose and then squeeze out any air that gets trapped, it is a bit of a process but all the air gets out of the system so I dont think it is a problem. I bought bleed screws to put somewhere there but they were never needed because that process worked and the set up worked like that without overheating.

JBurch said:

Check for a worn out timing chain, could cause cam and ignition to run retarded, causing an overheating problem. Easy to check, with distributor cap off, put a socket on the crankshaft bolt, rotate it around to "0" timing mark. Watch or have helper watch distributor rotor as you rotate crankshaft back, stop when it (the rotor) just starts to move, how many degrees did crankshaft move before rotor moved, the fewer, the better.

Click to expand...

Thanks it is a possibility so I will check it out!

If your inlet/outlet temps are not correct then your fan is not large enough (CFM) or your radiator might be clogged (yes it is possible) or your water pump isn't efficient enough or you could have air in the system. There are other options,,,but one at a time.

More later...

RustyRatRod said:

That electric fan looks like a cheap POS wal mart fan........no offense it really does look bad. You need about 4000 CFM of air flow to cool a high performance V8. BUT that still doesn't explain your highway over heating......unless it gets hot first and then never can cool off. I would start with the fan and add a shroud first. The mechanical fan might be a good idea. And if you do that, I would go with the Mopar Performance viscous fan package with a shroud. Lastly, all radiators AINT on the same level by a LONG SHOT. Did you get one of those Ebay chinkesium specials? Was it a chinkesium special from somewhere else? Those are hit and miss at best. Some cool great. Some won't cool from **** to shinola. One word on radiators. Griffin. If it runs hot with an appropriately sized Griffin in it, rest assured, you got another problem.

Click to expand...

The electric fan is a cheap POS your right but it pulls air pretty well. Thats my point though the fan should not make a difference. If I start the engine cold then go out and run constant a constant 50mph straight away it overheats anyway, fan doesnt help at 50 mph.

The radiator is unknown bought second hand so I had my suspicions, but it has worked and the original radiator which has also has worked no longer is enough to keep this pretty mild smallblock cold.

You also commented that the radiator is not clogged. How do you know? Have you had it flowed by a competent radiator shop? You could have a situation where the radiator has become restricted from rust and debris from the engine over time. You would not be able to tell unless you had the radiator flowed.

purplehazenils said:

The electric fan is a cheap POS your right but it pulls air pretty well. Thats my point though the fan should not make a difference. If I start the engine cold then go out and run constant a constant 50mph straight away it overheats anyway, fan doesnt help at 50 mph.

The radiator is unknown bought second hand so I had my suspicions, but it has worked and the original radiator which has also has worked no longer is enough to keep this pretty mild smallblock cold.

Click to expand...

The radiator will not cool at high speeds if air can get around it. I had to seal all the areas around the radiator and use a radiator support to hood seal.
One problem at a time, first check the inlet and outlet.
treblig.

Treblig said:

If your inlet/outlet temps are not correct then your fan is not large enough (CFM) or your radiator might be clogged (yes it is possible) or your water pump isn't efficient enough or you could have air in the system. There are other options,,,but one at a time.

More later...

Click to expand...

I have not checked inlet and outlet temps through the rad so that is a good point thanks!

However the fan shouldnt make a difference at 50 mph and the radiator it very tight up against the opening in the front, so its a pretty good seal. But there has to be something else wrong, with the way its overheating a tiny bit more air from a radiator support to hood seal probably wont solve it all. The pump looked good when I checked, the weird thing here is that this set up pictured and the set up the car came with (which should theoretically have less capacity) have both been sufficient to cool the car.

RustyRatRod said:

You also commented that the radiator is not clogged. How do you know? Have you had it flowed by a competent radiator shop? You could have a situation where the radiator has become restricted from rust and debris from the engine over time. You would not be able to tell unless you had the radiator flowed.

Click to expand...

I tested by just filling it multiple times and seeing that it emptied very quickly. So like your saying its not the best test. It is possible that it has become clogged, but its hard to believe that both radiators have become clogged while one in use and one on the shelf.

Incomplete combustion may affect O2 in the exhaust, but that is not measuring rich or lean. Rich or lean refers to the mixture in the cylinder at the time of combustion, which is entirely controlled by the fuel system. The composition of the exhaust gases is only an indicator of this.

Based on what you say you have tried, I am wondering if you caused a blockage in a water passage when you were replacing the freeze plugs; for example, driving part of a rusty plug inward. What did the interior of the water passages look like?

But I still think your electric fan is inadequate. It looks like the Autozone special I tried installing in front of my 273 Commando in younger days. The 273 was getting a little hot idling in traffic, but with the low-CFM electric fan, it ran hot all the time until I ditched it and put the metal fan back on.

Anyway, you should be able to tell if there is a cracked head or combustion leak into the coolant. With the motor running and the radiator cap off, are there bubbles in the coolant? Drain some coolant into a cup and sniff it -- does it smell like exhaust? Put your hand in the exhaust stream for a moment -- when you pull it out, is it wet? Does it smell like coolant?

Does the upper hose get hot? If not, you have air in the system, a bad thermostat ( I know you checked it, but...) or the water pump simply isn't working properly. I personally would suspect the water pump, as I have had issues like this in the past. You should be able to see coolant flowing rapidly in the system by running the motor with the rad cap off. If the problem is trapped air, there are several methods of "burping" a cooling system if need be.
Start with a cold engine. Remove the radiator cap and fill it to the recommended level with a 50/50 mixture of antifreeze and water. Make sure any auxiliary tanks are also at the proper cold fill level. With the radiator cap off, start the engine. Make sure your heater is set to maximum heat. You want 100% circulation of the coolant. Let the engine operate long enough to warm up enough to reduce the idle speed to a normal idle. Let it idle until it's at normal operating temperature, keeping an eye on the temperature gauge. Overheating can cause additional problems, obviously. Once the thermostat begins to open, don't rev the engine, even slightly, as this can force hot coolant out of the open radiator.
You might notice some air bubbling in the coolant out of the open radiator during warm up. This bubbling is normal if you have air trapped in your system, and is caused by the air escaping as it reaches the area of the open radiator cap. Unless the bubbling is excessive, continue to let the engine run at idle for a few minutes once it reaches normal operating temperature, then shut it down. Allow the engine and cooling system to cool off, preferably overnight. Then check your coolant level again. If it dropped, that means you've displaced some of the air in your system. Refill to proper levels, and repeat the process. Do this until the level doesn't drop any longer, then replace your radiator cap.

How much vacuum does the engine make during idling in neutral and in drive?

I have a fairly similar 360ci engine, powersteering, Doug's headers, only with a XE256 cam and 11.3:1cr.
My car has a fan shroud which really helps.
With the 160F thermostat it stays around 150F pretty much all the time, unless I get into heavier traffic, where it will climb to 160-170, 180 max. As soon I as hit open road it drops back to 150-160F.

What's the diameter size of the crank and waterpump pully? Can you locate and try a smaller waterpump pully perhaps?
I know the waterpump pully on my setup is roughly 14-15cm in diameter.

What are you using for a gauge? Are you really overheating? I recently lost the ground on my Autometer temp gauge. It would start cold and climb to 250 in less than 2 minutes. I repaired the ground and gauge dropped back to 180. No matter how inadequate your cooling system is, it should take 5 minutes or more to get to overheat condition. Verify your temp gauge is accurate before you chase other issues.

FYI- I paid $30 for the Malibu dual fan set up from a guy on craigslist. He had bought it new for his car then sold his car.

mvh said:

Incomplete combustion may affect O2 in the exhaust, but that is not measuring rich or lean. Rich or lean refers to the mixture in the cylinder at the time of combustion, which is entirely controlled by the fuel system. The composition of the exhaust gases is only an indicator of this.

Based on what you say you have tried, I am wondering if you caused a blockage in a water passage when you were replacing the freeze plugs; for example, driving part of a rusty plug inward. What did the interior of the water passages look like?

But I still think your electric fan is inadequate. It looks like the Autozone special I tried installing in front of my 273 Commando in younger days. The 273 was getting a little hot idling in traffic, but with the low-CFM electric fan, it ran hot all the time until I ditched it and put the metal fan back on.

Anyway, you should be able to tell if there is a cracked head or combustion leak into the coolant. With the motor running and the radiator cap off, are there bubbles in the coolant? Drain some coolant into a cup and sniff it -- does it smell like exhaust? Put your hand in the exhaust stream for a moment -- when you pull it out, is it wet? Does it smell like coolant?

Click to expand...

The interior passages of the lowest freeze plugs looked pretty bad like it the photo. I cleaned them out as well as I could. You just made me think of something .. Long story short one of the lower freeze plugs was replaced by a rubber one like shown ... could it have gone in too far and is blocking flow?

I have not checked for bubbles in the coolant or done the smell test. Exhaust looks clean but never sniffed it. I will check for bubbles in the coolant and check the exhaust tomorrow!

Garry in AZ said:

Does the upper hose get hot? If not, you have air in the system, a bad thermostat ( I know you checked it, but...) or the water pump simply isn't working properly. I personally would suspect the water pump, as I have had issues like this in the past. You should be able to see coolant flowing rapidly in the system by running the motor with the rad cap off. If the problem is trapped air, there are several methods of "burping" a cooling system if need be.
Start with a cold engine. Remove the radiator cap and fill it to the recommended level with a 50/50 mixture of antifreeze and water. Make sure any auxiliary tanks are also at the proper cold fill level. With the radiator cap off, start the engine. Make sure your heater is set to maximum heat. You want 100% circulation of the coolant. Let the engine operate long enough to warm up enough to reduce the idle speed to a normal idle. Let it idle until it's at normal operating temperature, keeping an eye on the temperature gauge. Overheating can cause additional problems, obviously. Once the thermostat begins to open, don't rev the engine, even slightly, as this can force hot coolant out of the open radiator.
You might notice some air bubbling in the coolant out of the open radiator during warm up. This bubbling is normal if you have air trapped in your system, and is caused by the air escaping as it reaches the area of the open radiator cap. Unless the bubbling is excessive, continue to let the engine run at idle for a few minutes once it reaches normal operating temperature, then shut it down. Allow the engine and cooling system to cool off, preferably overnight. Then check your coolant level again. If it dropped, that means you've displaced some of the air in your system. Refill to proper levels, and repeat the process. Do this until the level doesn't drop any longer, then replace your radiator cap.

Click to expand...

The upper hose gets hot as hell, same as the radiator. The water pump did however look fine though. I haven't had the heater on I will give it a go!

Everything I read here and taking into account all the symptoms would make me VERY suspicious of the water pump.
I have even seen some that the impeller came loose from the shaft.
If this is the case then coolant isn't circulating, and would cause an overheat under any circumstances, and with any radiator or any of the best parts out there.

Note that a gasket leak or a crack somewhere would cause coolant to be pushed out from building pressure just before it overheated.
If it doesn't puke coolant it probably not a compression leak.
(A radiator pressure tester will confirm this one way or the other, without needing to send a coolant sample away)