I have a 1998 F-150 with the 4.6L V8.

My coolant started puking out of the overflow reservoir. I noticed it after driving around for a while. Never happened just sitting there idling.

I purged the air from the system heat on high set to panel (per service manual)

Still the problem persists.

I re-did the purge following a different method. Heat on high set to panel. I left the overflow bottle open and let the engine get to operating temperature.

Here's what I noticed. The coolant level would rise in the bottle then overflow and drop way down. As soon as it would start to drop I would add more coolant never letting it suck air. A few more minutes would go by and the cycle would repeat. I'm thinking I'm getting rid of the air in the system.

After going through 2 gallons of coolant on an already "full" system. I start to suspect that there is something else going on.

Other observation, the upper radiator hose is hotter close to the radiator and cooler by the waterneck.

So, I'm thinking the water pump is bad and and coolant is boiling creating the periodic bubbles. I never notice the temperature getting passed the halfway mark during all of this.

Thoughts?

 

Maybe I wasn't clear. I'm asking for advice. Does it sound like the water pump or something more ominous? How can I tell if it's the water pump?

Thanks.

 

Sounds like bad head gasket. Puking is from exhaust pressure getting into the coolant and it needs to escape. Pushing out the fluid. It shouldn't puke when you have the lid off.
And your tsat gauge on ur cluster is buffered it won't move unless there is a drastic change or it's running really hot. It's meant to take the worry out of driving. Same with ur oil pressure gauge. And battery.

 

Aargh! That was the answer I didn't want to hear. I was clinging to the hope that it was the water pump. Any opinions contrary to the head gasket are welcomed.

Any idea what I can expect it to cost to have the head gasket replaced?

Thanks

 

Head gasket replacement can run 1500$ easily.
But u can buy gasket fix that u pour into ur coolant and it seals any holes. May work

 

Steel,
I work at prestone coolants. Also a auto mechanic. I would get your system pressure tested before you do anything else. You may be able to borrow a pressure tester from Autozone. This is a device that attaches to the cap and artificially pressurizes the system. You then wait to see if it holds pressure. If it does, likely you do not have a head gasket leak. Water pumps are tricky to diagnose without just removing it and inspecting the impellers. If you have cavitation damage on your impeller, it could cause symtoms similar to what you are experiencing. If i can be of further help, I do have lots of OE repair info i can share

 

im in the same boat as you, except ive gone to the point of pressurizing the system and no signs of leaks. i then checked the coolant for combustion and that came up negative. ive found that if i leave the cap loose, stop tightening just as it's grabbing it will not overheat. or after the first overheat if you crack the cap to release pressure it will run all day without a sign of overheat

 

There is also a letter from FORD that tells of many 98's filled with str8 coolant from the factory. I tried posting it but no luck. The fix was replacing the heads! Must be that the coolant gelled in spots inaccessable. Dont think that is your problem as your truck has surely had at least one coolant replacement

 

Ok, still having issues.

I missed the note about the pressure testing. I may have to check that one out.

On to my update. I have added replacing the water pump and serpentine belt to my list of things I have replaced.

So when I first start the car after it completely cools for several hours (morning or after 8 hour work day), the temperature creeps up to about 1/3 then drops to all the way cold. It then starts creeping back up to almost 1/2 way on the temp gauge. Then suddenly it shoots full hot and the warning light comes on. If I miss the warning light and keep driving it goes into "limp" mode and coolant starts forcing its way out of the coolant bottle. If I pull over immediately and shut the engine off I don't get the puking coolant.

What I have noticed is that all it takes is a second for the temp gauge to recover. Sometimes it does it on its own after I come to a stop. Sometimes, as in the video below, I just turn off the engine, and immediately key on(not start) and the temp is normal. The instant recovery would lead to think it was the Engine Coolant Temperature Sensor(ECT). But that doesn't explain why it would puke out coolant if I ignore it.

Also, once it goes through this cycle of jumping hot and going back normal I can drive it for hundreds of miles without having this problem again until the system cools down. Would a head gasket be a one time per start thing?

I have a video showing what happens. There are several minutes of nothing much so you can fast forward to around 4:50. In the case of this video, I was on the highway when it happened. That doesn't matter though since it happens at any speed under any level of acceleration, except complete idle. It can run forever at idle in the morning without an issue.

Help!

 

Temperature sending unit?
Or maybe ur fan clutch is bad so it doesn't turn causing it to run hot