Running HOT AGAIN

[MikeStang 247]

Ok i couldnt find my old post but here goes..

69 mustang, rebuilt 351, ALL stock crap, 2 barrel carb etc...

Car was running hot at idle but fine going down the road...

1st things we did were swap to a 6 blade fan instead of lettuce chopper 4 blade.

Ran hot still, but took a bit longer to run hot.

#2 swapped to a 180 thermostat....didnt help still hot at idle.

#3 Swapped from a 2 core radiator to a 4 Core Brand new radiator.

Temp stays 170 when cruising, then when u stop it goes to 180 pretty fast, then slowly creeps to 190, highest i let it get was about 193 and then got moving.

So here is the list of new stuff......4 Core radiator, 6 blade fan, new shroud, new water pump, and fresh coolant...I have no leaks.

There is no water in the oil, and no bubbles in the radiator, jacked car up to purge air, got nothing.

The only thing that makes me wonder is that when i put the 180 thermostat in and filled it with water, then let it idle with the cap off to see water drop and top it off once the thermostat opened, is that the water never really dropped, but i know the thermostat is working because when you cruising it will get to 182 and the temp will plummett to 170, then back up then back down. I know in all the past work i have done involving cooling systems, usually when u replace a thermostat and let the car warm up to operating temp, the water will drop when the thermostat opens, and you can usually squeeze a half gallon in there....This thing aint doing that....

Also when its idling with the cap off and reaches operating temp you dont see the water move in the water neck, unless you idle it up to about 1500 rpm's, then you will see the water start flowing, if you continue to raise the RPM it will really start moving hard and fast.

 

My thoughts are this.

I know the thermostat is working, the radiator is not plugged and doesnt really get so hot you cant touch it, and its not steaming and no water coming out the exhaust, BUT there is really no coolant movement at idle....So in conclusion I thing that the NEW water pump may not be moving fluid like ti should at idle, and may try a new flow cooler pump, Or that who ever built the motor may have knocked a freeze plug into the block restricting water flow...

What yall think.

Mike

[LoneWolf2U 136]

W or C engine?

Will make difference in figuring out the problem.

[MikeStang 247]

It's a 351 Windsor

[MikeStang 247]

Forgot to mention timing is set at stock setting and holds at idle with little to nonflictitaion.....I have even tried raising timing to help but to no avail.....all plugs look perfect and tan, don't remember last time I saw plugs that clean lol

[SM69Mach 68]

Are you running stock pulleys? Would it stay at 180ish at idle before you started having issues? What brand Water Pump?

[LindenBruce 27]

Well water boils at 212f in an open atmosphere at sea level. Add coolant and that goes up. Add pressure with a cap and it goes up again. Maybe 245-260f. So if you are getting to 193f at idle with your cap on and a 50/50 antifreeze mix I would think you are just fine. The factory 428 thermos were 195f if I remember correctly.

 

So I would think you are in the ball park. Is it boiling when you are idling the car? A lean mixture will cause it to run hot too. Bruce

[sportsroof69 13]

A RICH mixture will cause it to run hot.

[MikeStang 247]

Not sure of the brand of water pump, the owner put it on, its a cast iron unit is all i know....I try to steer clear of the stamped steel impellers tho, prefer cast iron impellers they seem to do better ALWAYS...Im wondering about the water pump backing plate to impeller clearance...on a pontiac if its too far it will run hot.....

Its not overly rich, you can stand in the shop with it running and it takes a while before the fumes get ya LOL

I know when it starts to get up to 190 ish that if you kill it, its tough to start back after about 5 min....so i was thinking its boiling the fuel off maybe?

The stock thermostat is supposed to be 192 degrees, Yes it was having heating problems when i started thats why i upgraded to 4 core radiator and yes they are the stock pulleys, i am going to have to swap to a smaller water pump pulley when i add the AC, this will speed the pump up a little bit but not sure if it will be enough

Mike

[SM69Mach 68]

Sounds like you have checked everything but the water pump. Could be something going on there. I would also agree that 193 is not terrible. Mine gets to those tmps in traffic sometimes on warm days but always comes down after it gets moving.

[sportsroof69 13]

I know you said that it's not rich, but difficulty hot starting the engine indicates that the idle circuit is rich, especially if it's only 190* and hard to start. I don't think that has anything to do with your water temp trouble, I was just throwing it out there as a bit if info.

[1969 Mach1 14]

Actually, for running a 180 degree thermostat your temps are pretty good. However, excessive rising temps at idle that reduce to normal when the vehicle is moving are indicative of insufficient air flow through the radiator at idle. Install a fan shroud if one is not already on it. Verify the fan to radiator spacing is correct. The fan manufacturer should have the specs for both with and without a fan shroud.

 

Another thought is make sure you have the correct water pump pulley. I don't know if yours has factory A/C, but, Mustangs with factory A/C use a smaller diameter water pump pulley than non A/C cars. This smaller pulley increases the water pump and fan RPM for increased cooling capacity. Even if your car is non A/C you can install the smaller diameter pulley.

 

Good Luck

[Max Power 74]

Yup. ^This^

 

If it runs hot ad idle, it's an airflow problem. If it runs hot at speed, it's a coolant flow problem.

 

All your overheating, if you could call it that, is happening at idle, and you are looking at coolant flow. If your car keeps cool at speed, your coolant flow should be fine.

 

I actually don't think a ten degree variation from your stat rating is that big a deal. But, I think you have an air flow problem at idle rather than a coolant flow one.

[MikeStang 247]

Car has a 4 Core radiator "Brand New" a stock fan shroud, and a Factory direct drive 6 blade fan....the blade spacing from radiator puts the fan so that approximatley 1/2 the blade maybe a bit more is inside the shroud......And get this....Its pulling enough air through the radiator that it will hold 2 bath cloths firmly on the radiator. This indicated to me there is plenty of air flow.

The water pump pulley is not the ac version, im looking for that one because the car is having the AC reinstalled....The pulley on the car now just barley contacts the lower factory Crank ac groove on the pulley, so yes its a bit bigger than the factory ac unit, but not taht much.

When the car starts to get 190 olus the radiator is cool enough to put your hand on the core area anywhere you want to and you can keep it there as long as you want to , and it doesnt ever really get uncomfortably hot.

When you look in the radiator at idle when the radiator is full, the coolant is not moving at all, its just sitting there and the thermost i know is open because when you increase RPM the water level drops a bit and coolant moves like crazy.

and when you just increase the rpm to move the coolant the temp will drop .

Swapping the water pump in the next few days, then installing the other water pump pulley.

Mike

[MikeStang 247]

Oh when it gets tough to start around 190 or so the engine also starts to run a bit rough.

 

The temp will go over 190...had it to 200 and shut it off, so i know it will eventually run too hot, adn the ac aint even on and the condensor aint mounted in front of the radiator so that wont help ANY

Mike

Edited September 15, 2011 by MikeStang

[buening 63]

+1 How far is your fan into your fan shroud, and is the shroud correct for the diameter fan you are running? 193° isn't hot at all, in fact it is better to run a bit warmer as it reduces wear on the engine. Newer cars typically run around 220° IIRC, which helps with both emissions as well as make the engine last longer.

[buening 63]

Well if it is running rough then you have issues besides cooling it seems. Better look into carb tuning and double check your timing.

 

How are you measuring the temps?

 

What water pump are you running? I recommend a FlowKooler if you are insistent on getting one. You should definitely see water flowing when the thermostat opens.

[MikeStang 247]

Car has a 4 Core radiator "Brand New" a stock fan shroud, and a Factory direct drive 6 blade fan....the blade spacing from radiator puts the fan so that approximatley 1/2 the blade maybe a bit more is inside the shroud......And get this....Its pulling enough air through the radiator that it will hold 2 bath cloths firmly on the radiator. This indicated to me there is plenty of air flow.

The water pump pulley is not the ac version, im looking for that one because the car is having the AC reinstalled....The pulley on the car now just barley contacts the lower factory Crank ac groove on the pulley, so yes its a bit bigger than the factory ac unit, but not taht much.

When the car starts to get 190 olus the radiator is cool enough to put your hand on the core area anywhere you want to and you can keep it there as long as you want to , and it doesnt ever really get uncomfortably hot.

When you look in the radiator at idle when the radiator is full, the coolant is not moving at all, its just sitting there and the thermost i know is open because when you increase RPM the water level drops a bit and coolant moves like crazy.

and when you just increase the rpm to move the coolant the temp will drop .

Swapping the water pump in the next few days, then installing the other water pump pulley.

Engine DOES NOT run bad until the car gets to 190, and at that point it gets tough to start after it has sat for 5 min to 20 min, once it cools a bit more it starts easily as always.

Im gonna try smaller ac pulley to begin.

Mike

[buening 63]

I'd recommend using a meat thermometer pressed into the radiator core fins to confirm the temps you are reading. If you have an infrared temperature gun, test the engine block as well as the radiator core and let me know what you are reading. This will confirm that your temp readings are within reason and that you don't have a steam/air pocket below the temp sending unit.

[LoneWolf2U 136]

No coolant flow at idle but flows at 1500 rpm.

I would look at better pump or smaller pulley to get the coolant flowing.

Remember the stat to be completely open is 7* more than listing, So a 180* stat will be in its fully open position at approx 187*.

 

A good flowing coolant system will be moving coolant thru it at idle.

It should be passing by the neck opening like a slow moving stream and increase flow rate as engine speed increases even slightly.

[LindenBruce 27]

If the timing is too far out of adjustment, advanced or retarded, it will cause starting issues as well. Bruce

[1969 Mach1 14]

Like Mach1Rider said, the 180 degree stat won't be completely open until about 187 degrees. That's pretty accurate with every stat I have checked in a pot of water on the stove. If your radiator is cool and temps are 190 degrees and above with the 180 degree stat, it is obviously not open. If you haven't already, I would recommend using a high flow thermostat. I don't know if they actually flow more but they seem to have more consistant opening and closing temps. If you can't get a high flow stat at least use a good quality stat like the Stant superstat and drill a small 3/32 or 1/8 inch hole in it. This hole will help bleed out any air pockets and balance the coolant pressure on both sides of the stat when it is closed. The thermostat will operate more consistantly with equal coolant pressure on both sides of it. The high flow thermostats are advertised as being "balanced" and they come with these bleed holes.

[Lemon Owner 11]

Just as a matter of interest do you have the thermostat around the correct way? It has been a long time since I removed one but I am pretty sure they can only go one way to work correctly. The wrong way round would explain why your radiator is cool.

[MikeStang 247]

Ok,

The shroud is on correct, this 4 core shroud will onlu go on one way lol.

The thermostat will go in backwards, but it is in correct "actually have found some installed backwards before LOL

The thermostat is a Stant, and has the bleed hole in it

I know its opening between 182-186, because when your cruising it gets up to about 182-186 "Depend on how accurate the guage is", then once it reaches this temp, the temp then drops down to the 165-170 range, then starts its ascent back to 180's and then falls again, its regular as clock work, so i know its opening.

I apreciate all the info you guys are providing, but wish all of MY posts got read so we would all be on the same page and i wouldnt have to repeat all the answers i answered in previous comments LOL

Gonna shoot for timing tonight and see what happens, then try carb, which i am sure is spot on, then water pump pulley, which i have to swap out anyhow to put the ac back on, then last resort water pump, and very last resort, only driving when its cool HAHAH

Mike

[LoneWolf2U 136]

Check the timing as it will cause hard cranking when warm if it is too far advanced.

As for the cooling problem, I would swap pulley out for a smaller one on the pump first. Your discription of no coolant flow at idle means the pump is not turning fast enough at lower rpms to keep it moving.

[buening 63]

.....or the pump is bad or the coolant passages are plugged.