Baffled. Overheating issue

[cobrajet69]

2009 5.4 GT500. Usual bolt on mods & tune. Dual fan heat exchanger.

So about a year ago I was cruising down the street at about 45 miles an hour and the car overheated. Got home and determined it was probably just a thermostat. Replace the thermostat and everything was fine for about a year.

Well, a month ago same thing happened but it happened while I was on my way home from work. Addison to Keller. Figured it was a thermostat again and replaced it with an OEM Ford piece. The previous one looked fine but figured it had to be the thermostat. Drove it for a few days then to work again and on the way home it overheated again. At this point I'm not really sure what's going on, or what's causing the overheating but the blowoff is coming out of the pressure sensitive cap on the refill box. Which leads me to think thermostat again but not sure.

Only correlation between all three events is the fact that I had played tag with another vehicle on each event. With the last one being a Porsche Turbo cruising down 114 in Grapevine and the car didn't overheat until I got all the way to Keller. Temperature was running perfect the whole time and then all of a sudden it just started heating up. The same thing happened on each event, where the car overheated several minutes after the run.

Not running premixed antifreeze but don't believe the ratio was so far off it would cause it to overheat. Kind of at a loss here.

Any help or suggestions would be greatly appreciated.

David

[KBScobravert]

I know your don't want to hear this but might be time to check and see if your getting cumbustion chamber pressure in the coolant system under high boost.

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[Rick Modena]

I'm assuming the radiator cooling fan was running when you pulled over? I would check the H/L fan relay connectors as some early models had wiring issues where the connectors burn at the connection.

[cobrajet69]

I know your don't want to hear this but might be time to check and see if your getting cumbustion chamber pressure in the coolant system under high boost.

Sent from my SAMSUNG-SM-G890A using Tapatalk

I would think there would be other indicators if that were happening. Sure as hell hope that's not the case!

I'm assuming the radiator cooling fan was running when you pulled over? I would check the H/L fan relay connectors as some early models had wiring issues where the connectors burn at the connection.

You know, now that you mention it, I don't recall hearing the fan running. Def worth checking out.

Thanks gents!


David

[46Tbird]

I would definitely get one of those cheapo AutoZone head gasket test kits that check for hydrocarbons in coolant. Just to rule that out.

If it finds something, I would try a re-torque on the head bolts before yanking anything apart.

If it doesn't, I would check the fan electrical as Henry mentioned. I would say you might be experiencing water pump cavitation at high RPM, but even that doesn't sound right to me. I'm not aware of any mod-motor or GT500 specific issues with overheating after a run.

[cobrajet69]

Thanks D!



David

[Broncojohnny]

You need to check into your fan. The fans are notorious for fucking up on those cars. Check out this thread for some good info:

http://www.teamshelby.com/forums/index.php/topic/69745-gt500-overheating/

[Sean88gt]

Definitely check the head gaskets. A small failure can pressurize the system, leaving you chasing your tail because there are no other symptoms.

But, I'll give you a grand, sounds like a total loss.

[Z06killinsbf]

This only leaked under boost. Normal driving it was fine

[Baron Von Crowder]

This only leaked under boost. Normal driving it was fine

mod motors have MLS gaskets, they arent prone to blowing.

[svauto-erotic855]

the blowoff is coming out of the pressure sensitive cap on the refill box.

Are you meaning to say that coolant is being forced out of the system? You may be having localized boiling in the system that forces out coolant and that chain of events leads to over heating. Start by changing to a 40/60 coolant to water mix, check that the impeller is tight on the shaft in the water pump, and make sure your belt is not slipping. If you do all that and still have problems chances are that you have a bad head gasket.

[cobrajet69]

Are you meaning to say that coolant is being forced out of the system? You may be having localized boiling in the system that forces out coolant and that chain of events leads to over heating. Start by changing to a 40/60 coolant to water mix, check that the impeller is tight on the shaft in the water pump, and make sure your belt is not slipping. If you do all that and still have problems chances are that you have a bad head gasket.

I'm hoping this is the case. Going to drain and refill coolant this weekend. Will check for hydrocarbons as Danny suggested while I'm at it.



David

[Fourx4Brad]

Have you done a radiator system pressure test?

I had something similar happen back in August of last year. On random really hot days after 30 minutes of highway driving (home-work traffic) my truck would blow off steam out the overflow tank.

I have a 10 year old truck with 140+ thou miles so at first I replaced the thermostat with new antifreeze, etc. After the third occurrence I was thinking a leaky head gasket so I borrowed a radiator pressure test kit and determined the radiator system held 15 lbs of pressure (cold and at normal operating temp). I temporarily switched the overflow cap with a neighbors spare vehicle for a day and found the issue. The overflow tank cap was no longer sealing properly. I bought a new overflow cap the next day and its been 9 months without a re-occurrence.
Brad

http://www.harborfreight.com/radiator-pressure-tester-kit-69258.html

[cobrajet69]

Have you done a radiator system pressure test?

I had something similar happen back in August of last year. On random really hot days after 30 minutes of highway driving (home-work traffic) my truck would blow off steam out the overflow tank.

I have a 10 year old truck with 140+ thou miles so at first I replaced the thermostat with new antifreeze, etc. After the third occurrence I was thinking a leaky head gasket so I borrowed a radiator pressure test kit and determined the radiator system held 15 lbs of pressure (cold and at normal operating temp). I temporarily switched the overflow cap with a neighbors spare vehicle for a day and found the issue. The overflow tank cap was no longer sealing properly. I bought a new overflow cap the next day and its been 9 months without a re-occurrence.
Brad

http://www.harborfreight.com/radiato...kit-69258.html

It's a thought but this cap locks under pressure (won't let you remove until pressure/temp drops) so I'm guessing it's working properly.



David

[Rick Modena]

Now that Alan has posted that link, I'm almost positive thats your problem. After reading that thread I would replace the fan and relay link/harness asap. Also, straight water with WaterWetter and your good to go...