5.0 Overheating problem

[mike8066]

Guys, I have a heating issue that I cannot, for the life of me, figure out!

Here's the issue. I put in a new 5.0 short block. The motor has less than 50 miles on it. It was running good for a week or so (hence the 50 miles), then it suddenly started overheating. The temp will slowly rise to about 200, then move quicker to 220, after that it spikes - I mean literally JUMPS to 230-240. That's when I scramble to kill the engine.

I pulled the heads, thinking it was a head gasket. Sent them to the machine shop for reconditioning, cleaning, magnafluxing, and resurfacing. Put them back on the motor with FelPro 9333 gaskets. Drained and flushed the oil. Replaced oil and filter. Also put on a new water pump, intake gaskets, thermostat, and installed a new 3 core radiator.

When it was all done, I fired it up, giving it a few minutes to evacuate the air out of the system. Everything looked good, then after 10 minutes of running, it did it again!!! The upper rad hose was still cold. Like the thermostat didn't even open (it's the 4th thermostat I've installed troubleshooting this issue!) WTF??

I'm out of ideas.

Mike - 95 Cobra SVT 5.0

 

[SublimeRT]

How many miles are on your car? How's the heater core and heater core lines/hoses? Radiator cap? Serpentine belt tension? Belt routed correctly?

 

[Chythar]

Are you sure that the engine is overheating? One of the coolant temp sensors may have gone bad, or your gauge may have gone bad. The only way to know what's happening is to get a code reader that reads PIDs (engine sensors stored in the computer, basically). That will tell you what the computer sees, which is coming from the ECT sensor. If it's bad, the computer will keep the engine in warmup mode and you will eventually overheat. If the sensor is bad, the value seen in the computer will jump all over the place.

 

[toyman]

If the upper hose is cold and soft the T-stat isn't opening. Test T-stat in a pot of boiling water and make sure the orientation is correct in the housing.

 

[HISSIN50]

Are you real sure it's burped? It can take more than idling to get a large pocket out. If temps climb faster than seem reasonable, an air pocket is likely.

 

[mike8066]

SublimeRT, there are less than 50 mi on the new engine (138K total vehicle miles). The heater core doesn't leak and heater works good. All hoses, including heater hoses were checked and flushed. Radiator and cap have been replaced with no effect on the problem. Belt tension is normal and belt routing is the same as it was prior to this problem. My car has the smog pump deleted, which only allows the belt to be routed one way.

Chythar, I have two gauges (one mechanical and one electric) in two different locations and they are both showing the same results, so I believe the gauges are functioning correctly. You are correct that I don't get any check-engine or warning lights. The coolant temp sensor and temp sender switch have been replaced.

toyman, I've replaced the t-stat 4 times and even tested it without one to check flow. Sometimes it allows the upper hoses to get hot and firm, showing that water and pressure is there, but other times it doesn't. So IDK.

HISSIN50, No, I'm not positive about the burp. I noticed it was still expelling a few dime-size bubbles after 10-min, but running it is the only way I know to burp it. How can I ensure that it is fully burped? Because you're right, from a physics 101 standpoint, the spike does sound like an air pocket, but I don't know how to get it out and confirm that the engine is burped.

Thanks guys!

 

[revhead347]

I'd fix the thermostat first. The top radiator thermostat should always get firm and hot. If you got the thermostat from an autoparts store, 4 in a row wouldn't surprise me at all. All the autoparts stores sell Stant thermostats, and they are junk. Always go to Ford and get an original thermostat. Or get a Mr. Gasket hi flow.

Kurt

 

[mike8066]

Kurt, You're right, the t-stats I've used are Stants. I looked around and found a Mr. Gasket High-Performance Thermostat #4364 180deg. (and #4365 195deg). I'll pick one up after work. Thanks.

 

[revhead347]

Keep in mind with the high flow, you're probably not going to have much for heat in your car. It directs too much water to the radiator, and not much gets up to the heater core. It helps a lot with cars that generate a lot of heat, but if you have a basic engine, a factory one should be fine.

Kurt

 

[mike8066]

Yeah, I understand. But, the way I see it, if I can troubleshoot and find an issue for $10-20 and a simple change, such as a t-stat, then it's worth it. If the Mr. Gasket t-stat confirms the problem, then I can get a Ford Dealership replacement afterwords.

Thanks.

 

[ProKiller]

i've always done the same thing to burp it, but also squeeze the upper hose to put more pressure in the system. they do make fancy contraptions to burp the system.

 

[Bullitt95]

Are you real sure it's burped? It can take more than idling to get a large pocket out. If temps climb faster than seem reasonable, an air pocket is likely.

Exactly what I'm thinking. The easiest way to burp the cooling system is to start the engine from cold with the radiator cap off and let it idle. Immediately after you fire up the engine the level inside the radiator will drop, so SLOWLY top up the system until the coolant level is at the bottom of the filler neck. Squeeze the upper hose intermittently to evacuate any more trapped air. When the coolant starts to rise up the filler neck and stops bubbling, replace the radiator cap and go for a drive. Make sure that there's enough coolant in the expansion reservoir 'cause any remaining air in the system will get burped in there. As the engine cools down after the drive cycle, coolant from the reservoir will get drawn back into the radiator to fill the space left by the air that was burped out.

 

[HISSIN50]

I'd add that jacking the driver's side front end can help (gets the rad neck higher). A cooling system funnel can help too. Just be careful of hot coolant squirting out. When a big pockets makes its way up, coolant can fly.

 

[mike8066]

Thanks guys! I'm gonna change the upper and lower rad hoses (no telling how old they are!) when I get home and put in the Mr. Gasket t-stat. After doing that, I'll need to refill the system again, which will require another burp. I'll try your advice and let you know how it goes.

 

[mike8066]

OK Guys, we're getting warmer (excuse the pun...). I changed the upper and lower rad hoses, and installed the Mr. Gasket Hi Flow 180deg t-stat. I used your advice on burping, and jacked up the front of the car to make the filler neck the highest point, ran through your steps to burp the system.

This time the car ran for 15min, holding at 165deg. I put the rad cap back on and within 3-4 min, it once again shot up the scale, jumping from 165 to 229 in about a minute or so. But this time it did something a little different than before. When it got to 229, it stopped and held at that temp. Still too high for my taste, especially rising that fast and with a 3 core radiator, but it's a start...

The t-stat opened perfectly, and the fans kicked on when they were supposed to. It seems the entire system is working the way it should, yet it is still spiking in temp and getting too hot.

There's no steam coming from the tail pipes. And I removed the rad cap and it boiled over (which tells me the gauge isn't giving a false positive. It really is getting that hot!)

So.... We're no longer hitting the 240+ mark, but it IS still getting too hot too fast.

 

[Bullitt95]

Sounds like you might still have some air trapped in the system.

 

[toyman]

Or a timing issue. Has anything been done that would cause the timing to be anything other than what you expect? I would confirm settings.

 

[HISSIN50]

Sounds like you might still have some air trapped in the system.

Agreed.

To stablize at 165* and then jump 65* in a few minutes thereafter isn't reasonable.

The cap and pressure in the system will keep the air from purging.

You might need to repeat the burping cycle, but this time cover the open radiator neck (so you don't get burned or damage anything on your car) and then goose the throttle a bit. You can have turbulent air and coolant gushing out once the stat is open and while you're goosing it.

 

[mike8066]

OK. I'll doublecheck the timing and let you know where it's at.

I'm starting to think that air in the system is a more reasonable possibility, mainly due to the fact that it's better now than it was (although still hot), and nothing was changed except the t-stat, hoses, and a better purge. After checking the timing, I'll run it again without the cap for a bit (but covered), goosing it occasionally and see if it gets better.

I have never had this much trouble getting air out of a system! This is insane! LOL!

 

[mike8066]

Just out of curiosity, any ideas of what a good temp range would be to look for? The engine is pretty well stock, with underdrive pulleys and the 3 core radiator. 180* thermostat. Current weather is sunny, 95*.