'86 5.0 blows coolant *everywhere*.

[4000 Pounds of Iron]

OK, I've been fighting this one for a couple weeks. I'm now on Water Pump #3 (the gasket under the backing plate is apparantly the weak link) and I'm still blowing enough glycol to poison all of Nashville.

As the car warms up, everything seems normal for a few minutes. The radiator drank about two gallons of 50/50 so I know there's no big-ass air holes in it. The highest point of the Mustang cooling system is the upper rad hose, so that's full of air regardless.

After about five minutes, the temp gauge starts to climb, and I'm goosing it a little, maybe 4k RPM, when the gauge suddenly leaps from 140 to about 220, and the radiator overflows (I'd been warming it up open to try to aid the circulation). I let it sit and run for a few more minutes, but the temp stayed up at 220, so I shut it down and came up here to ask for help.

The car behaved this way before as well, but I had a brand new 195 thermostat in it at first, Now it's got a brand new 180. The last couple times it blew, I had a 15lb cap on it, and it blew out the waterpump's backplate gasket instead of lifting the cap. I bought a 7lb cap but I haven't even had a chance to put it on, it overheated too quickly.


I think I'm going to try it without a thermostat, just for kicks. Anybody know what temp a wide-open radiator would let a 5.0 get to in 30 degree weather?

4k#Fe

 

[Blk91stang]

I had this EXACT problem with the EXACT symptoms, went through about 4 thermostats thinking they were the problem. I am 99.9& sure that my method will fix your problem. It's defiantly worth a shot.

Take your current thermostat out, drill two 1/8" - 3/16" around the innermost part of the thermostat to relieve any pressure inside the system. This will bleed the system of all the air. Start the car with the cap off and you will see coolant being cycled through the radiator and your coolant level drop. Keep a gallon handy and quickly refill. Drain your overflow to the proper level if it's filled to the top because of your overheating.

The problem is you still have air trapped in the system. Yes, I've done every method possible also and still had problems. Even though your radiator is filled, doesnt mean the motor is also filled up. These holes bleed the motor and let the coolant push all the air out

Trust me on this one. I will put a dollar on this that this is your problem. If you need a diagram of what I'm talking about, just let me know. Good luck

I was bored so heres a diagram of what I'm talking about..

 

[just4bob50]

man Im having similar problems with mine except Im not blowing antifreeze all over. 3 weeks ago I replaced my water pump, radiator and, thermostat. All was great until about a week ago when I started having problems with the temp spiking but only on cold start ups. Gauge would get about 3/4 of the way up and them the therm. would open and I could drive the rest of the day with no probs. Then the other night the car completely overheated and it almost started to puke antifreeze. I just replaced the thermostat this morning and now I read this. i was going to take it to get flushed but now I will try your Idea.

 

[795.0pacecar]

I had this EXACT problem with the EXACT symptoms, went through about 4 thermostats thinking they were the problem. I am 99.9& sure that my method will fix your problem. It's defiantly worth a shot.

Take your current thermostat out, drill two 1/8" - 3/16" around the innermost part of the thermostat to relieve any pressure inside the system. This will bleed the system of all the air. Start the car with the cap off and you will see coolant being cycled through the radiator and your coolant level drop. Keep a gallon handy and quickly refill. Drain your overflow to the proper level if it's filled to the top because of your overheating.

The problem is you still have air trapped in the system. Yes, I've done every method possible also and still had problems. Even though your radiator is filled, doesnt mean the motor is also filled up. These holes bleed the motor and let the coolant push all the air out

Trust me on this one. I will put a dollar on this that this is your problem. If you need a diagram of what I'm talking about, just let me know. Good luck

I was bored so heres a diagram of what I'm talking about..

You could try that but you shouldn't have to. I've changed a ton of thermostats with no problems, in fact I put a high flow 180 in my car today and it works fine. Last time I had the system fully drained I didn't refill the radiator untill the engine was warm enough for the thermostat to open, then while it was running I filled it.

You do have the belt routed correctly right?

 

[dyb003]

The 5.0 where very know for this prob after doing any work like that. There should be a bleeder valve on top of the engine. They are usualy white. You opne this while you are filling the rad back up. Sometime what has worked for me also is fill the rad up and then just run the engine till it gets good and worm, then shut it off and let it cool back down. Open the cap and fill it again. start the engine and keep toppoing off as needed as the vapor lock will be gone.Then it usualy will be ok. That usualy works for me anytime I have done any major work like that. Good luck

 

[Blk91stang]

You could try that but you shouldn't have to. I've changed a ton of thermostats with no problems, in fact I put a high flow 180 in my car today and it works fine. Last time I had the system fully drained I didn't refill the radiator untill the engine was warm enough for the thermostat to open, then while it was running I filled it.

You do have the belt routed correctly right?

I've changed my thermostat many times already also with no problems in the past. First time it ever gave me a problem and this was the solution.

I also happened to see this on "Two Guys Garage" a day after I figured this out. They stated to do the same thing on every thermostat install. People with temp spiking, its def worth a shot. I mean, it's easy enough to do.

 

[just4bob50]

I had this EXACT problem with the EXACT symptoms, went through about 4 thermostats thinking they were the problem. I am 99.9& sure that my method will fix your problem. It's defiantly worth a shot.

Take your current thermostat out, drill two 1/8" - 3/16" around the innermost part of the thermostat to relieve any pressure inside the system. This will bleed the system of all the air. Start the car with the cap off and you will see coolant being cycled through the radiator and your coolant level drop. Keep a gallon handy and quickly refill. Drain your overflow to the proper level if it's filled to the top because of your overheating.

The problem is you still have air trapped in the system. Yes, I've done every method possible also and still had problems. Even though your radiator is filled, doesnt mean the motor is also filled up. These holes bleed the motor and let the coolant push all the air out

Trust me on this one. I will put a dollar on this that this is your problem. If you need a diagram of what I'm talking about, just let me know. Good luck

I was bored so heres a diagram of what I'm talking about..

I would just like to let you know that I tried your advice with the thermostat and It worked great. The cars temp stays consistant and I have plenty of heat. I just order a water temp guage from Stewart Warner to have an accurate temp reading. If I were to do anything different I would probrably just drill 1 hole the next time as it took a little while for me to start getting heat in the morning, but once it warmed up the heat stayed fine. Thanks for the advice.

 

[Blk91stang]

I would just like to let you know that I tried your advice with the thermostat and It worked great. The cars temp stays consistant and I have plenty of heat. I just order a water temp guage from Stewart Warner to have an accurate temp reading. If I were to do anything different I would probrably just drill 1 hole the next time as it took a little while for me to start getting heat in the morning, but once it warmed up the heat stayed fine. Thanks for the advice.

Yea, I was gonna mention warm up time being longer in the winter. 1 hole would be more ideal for heat but I just wanted to make sure even if 1 hole got covered by rtv, you would have another to make sure. I have 3 and sometimes it only gets up to 140 degrees tops:: just enough to keep me warm

I'm glad it worked out for you!