Overheating

[Ward]

My 99 EB 5.4 overheated last night, and I'm not quite sure why. I just replaced the radiator, water pump, fan clutch, thermostat, and radiator hoses over the weekend, and it was driving fine all week until last night. I was driving down the highway doing about 60, and I noticed the temp gauge had moved up nearly to full hot. I got off the highway and pulled over, to find the overflow tank boiling. I removed the cap to let it depressurize, and let it cool for a bit. I then started the engine, and with the engine idling in park, the temperature stayed at the middle mark. I did notice though that with it running, I was getting a lot of little air bubbles coming up through the overflow tank. I got back on the highway, and the temp started climbing again after only a mile or two, so I pulled over again. I again depressurized it and let it cool, and this time I left the cap off the tank, thinking there was an air pocket in the system. I started heading home on side streets, and made it several miles before it boiled over and puked out a ton of coolant. After letting it cool some more, I added 2.5 gallons of water, and let it run for a few minutes. The temp stayed at the middle mark, and this time I was getting no air bubbles in the overflow tank. I drove it home with the cap on loosely, and the temp was normal the rest of the way. I'm thinking either my new t-stat is faulty and sticking, or a head gasket is allowing combustion gasses into the coolant. I'm going to get a block test kit, and check the coolant for exhaust gasses, but other than that I'm out of ideas. Has anyone had a similar problem?

 

[jbanks]

Might try getting more air out of the system.

Here's the only decent thread I could find.
How to "BURP" your cooling system - Ford Truck Club Forum

I think

 

[Ward]

Yeah, I did that when I replaced the radiator and stuff over the weekend. I guess it's possible I didn't get all of the air out, I will definitely try and bleed it some more.

 

[stamp11127]

If you can park on an incline so that the surge tank is the highest point in the cooling system it will be easier to bleed. After doing that, if you still get bubbles in the surge tank it points to a blown head gasket or cracked cylinder head.

 

[Ward]

Well, I bled the cooling system again. This time I parked on an incline, let the engine run up to operating temp with the coolant cap off. I didn't really have any big air bubbles come out, and I made sure the level was where it should be. I drove it all around the neighborhood, down side streets for 30 minutes or so and the temp was fine. I got on the freeway, and the temp immediately started to climb as soon as I got up to 60. I got it back home with the temp gauge near the red, and the coolant boiling in the tank. I checked for exhaust gasses in the coolant using a block test kit, and it showed negative.

I'm baffled at this point. I am going to try a new radiator cap, and I'm gonna switch out my brand new thermostat for a motorcraft one.

 

[toms89]

If you can park on an incline so that the surge tank is the highest point in the cooling system it will be easier to bleed. After doing that, if you still get bubbles in the surge tank it points to a blown head gasket or cracked cylinder head.

x 2

 

[Ward]

I didn't get any bubbles in the coolant, and the block test kit tested negative for exhaust in the coolant tank. I haven't ruled out a head gasket leak, I guess it could be intermittent.

 

[toms89]

I didn't get any bubbles in the coolant, and the block test kit tested negative for exhaust in the coolant tank. I haven't ruled out a head gasket leak, I guess it could be intermittent.

The cap is an important part of the system as pressure raises the boiling point. I believe the cap is rated to hold appr. 14psi pressure before it releases.

I doubt it is the issue but very cheap to replace and definitely worth a shot.


Not that it confirms anything but many years ago I had the exact same issue with my 89 mustang. Went through the same steps almost to a T down to have the radiator tested for exhaust gasses. It never did confirm any but it progressively got worse and it turned out to be a leaky head gasket. It appears it would only leak under load, possibly lifting the head, so it would not show up when the coolant was tested for exhaust gasses. It would just mysteriously and suddenly overheat as air was introduced into the system.

 

[stamp11127]

I read your original post again for more clues. Two things stand out, one is "adding 2.5 gallons of water" with the other being "and made it several miles before it boiled over and puked out a ton of coolant".
Head gasket, plain and simple. I have an Escort that did the same thing and is now a summer project. Might take the easy way out on it and get a crate engine from Ford.

 

[Ward]

Well, I believe I have solved the problem. The short answer is, the (brand new) radiator was plugged with sediment. The coolant was nasty when I got this truck, and I guess by flushing it and replacing parts last weekend, I dislodged a bunch of sediment that gathered in the radiator.

I decided to try flushing it again today, and put a new motorcraft thermostat and coolant cap on. When I went to drain the radiator, I noticed it was draining much slower than expected, I was only getting a dribble of coolant. That made me suspect a blockage, so I decided to pull the radiator out and check it. I managed to flush probably 2 handfuls of sediment out, it looked like black sand. I spent about an hour flushing the radiator until no more sediment came out, and I also spent a good hour backflushing the engine for good measure. I also installed the new overflow tank that I ordered, the old one had some rust build-up in it. I test drove it a few miles on the freeway and the temp was rock steady at the middle mark, so I'm pretty sure it's fixed, no blown head gasket after all.