really wierd overheating problem

[bgjohnson]

okay here's the problem. i recently did a cam swap in my friends 93 LX and put a one core or 2 core alum radiator and water pump in it also. it has 45k on it and has sat for some of it's life. and the first time he took it out after the cam swap i had way to much timing on it(pinging bad) so i turned the timing down by ear and got it running really well. i bled the air out of it a few times and drove it about 15 miles and i ran really good an really cool. then he comes and picks it up he gets about half way home and the thing pegs to 270 real quick. so he shuts it down and pops the cap and lets some steam out and fills it up. the he almost gets home and it does it again. now i give him a spill proof funnel and have him burp out all the air. and it is running fine while idling, but he takes it out and once he got on the highway about 5min into it it pegs the gauge again and the overflows out of the overflow. so came over today and put in a new T-stat(180) and radiator cap, burp all the air out of it and go for a ride. we get a little farther but it still it pegs the gauge all the way and spits out through the overflow. we burp the system and limp another couple miles, burp it again. but the temp still won't go down. so as of now i'm kinda stumped, although i do have an idea that maybe there is a clog in the system, because you can see where sombody put in "stop leak" tablets because of all the bits of that crap everwhere. and the old radiator seemed kinda corroded. so please any idea would be greatly appreciated. sorry for the long post.

 

[jerry beach]

You know a head gasket comes to mind when its boiling out water. Mine was doing strange things like losing water all the time. I had to keep adding or the temp would start to get erratic. I tried a 160* and 180* stant T-stats, put in a Mr gasket 180* and all is well. It stays full, go figure. I have a 3-core copper rad and elec. fan. The fan helped more than the rad, which I did first.

On second thought, you may not have enough radiator. The cap could be bad also. If its weak it can let out water when it shouldnt, causing the overheating.

 

[bgjohnson]

yeah we already replaced the cap so we could rule it out. and another interesting thing is we put in a fail safe T-stat, the thought behind it is when it fails it will fail in the open position, soo guess what is looked like when we pulled it, yeah it was stuck in the open position. well the radiator should cool better when it's on highway. and i think the radiator should be big enough it's aluminum and it's a little bigger than stock. this overheating thing is really makin me angry.

 

[HISSIN50]

do you have access to a cooling system pressure tester? you could see if it is holding pressure with one.

good luck.

 

[jerry beach]

If the rad can cool it at idle, but not running down the road then the rad is not good enough. If you have cooling probs at idle, it usually the fan. My fan keeps the temp under 180* at idle. Running at 80mph with the fan off will raise temps a bit, turning the fan on will drop them back to normal. The motor makes more heat running under load and that can exceed the heat transfer your rad can provide. If I run at 70mph, the fan does nothing.

 

[leakyfaucet]

I've heard of people putting the T-stat in backwards, but even if you did that, the fact that it was stuck open should keep it from being a problem.

Try removing the T-stat altogether and see what happens.

 

[PNY PWR]

I would do a good flush and go with a high flow 180* t-stat. I was having some issues after the paxton install so I threw in a high flow PPI 180* t-stat that completely fixed the problem. I run an electric fan and a copper 3 core radiator.

What kind of fan is he running? If it's a stocker, is the clutch good? Water pump good?

If you do all these things and go to fill the system try these suggestions. Go ahead and fill it as much as it will take cold. Crank it up and let it get up to temp. and circulating (also make sure it is in fact circulating good at this time and the pump's not got a problem), leaving the cap off. Keep filling it every lil bit while watching the temp gauge so you don't overheat. When it just won't take anymore, one of you rev the motor to about 3,000, the level will drop, have the other fill it while it's revved up, put the cap back on while it's still revved. Next fill the reservoir to the full hot mark. I've had alot cooling problems over the years in various Mustangs. All of the things I've put in this post have worked well for me to cure the 5.0 cooling issues. They can be very picky sometimes and will let you know about it quick.

 

[ratrapp]

you need to check the timing with a light.a car thats too low in time will cause it to overheat.a friend of mine has a 65 mustang with a mild 289.he set the timing by ear and it overheated.he changed t-stats,waterpump,added a big aluminum rad,eelectric fan,etc.i came up and set the timing and it never overheated again.another thing to check is make sure you have the right direction waterpump.

 

[PNY PWR]

Good point, I forgot he set the timing by ear.