1999 F150 6 cyl. 4.2 233,000 miles


My temp gauge went way high on the interstate so I assumed I had a bad thermostat. replaced it with a genuine Ford themostat, added coolant and here's where I'm at.

1. Let it idle up to operating temp. When it was warm, the heater was blowing cold air.

2. Thermostat opened up, top radiator hose was hot and full of coolant, still no heat in cab.

3. Took it for a ride on the hwy. Heat started to work in cab, temp gauge went way up. I slowed down and went home down a side road. Temp gauge went back to normal and stayed there. Only driving about 30 mph.

I don't get why I'm overheating at 60mph. My best guess is I have some sort of obstruction in the cooling system. Anybody ever had this happen?

thanks,

carl

 

if its warm and blowing cold air... you don't have the system full of antifreeze, you have an air pocket...
The gauge spikes, then drops back to normal after a minute -- same thing, air pocket.

Not saying what cause the ORIGINAL problem, but you need to get the radiator fill after you have the new thermostat.

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or your water pump is shot and not pumping any fluid.

 

Bad water pump?

 

I figured it out. I found another thread with the same issue. It's a bad head gasket that lets air into the coolant system. The air pocket is up high where the temp sensor it that what causes the temp spike.

So now my problem is what to do with this thing. 200k miles and needing a head gasket. I'm tempted to replace the whole engine with a low mileage junk yard one. I am not able to do the job myself and the head gasket is a big job. I'm thinking I might be money ahead to just put a new motor in it. Everything else in this truck is in pretty good shape. Body looks new.

any opinions?

carl

 

before you do that, put a bottle of BARS COPPER GASKET SEALER into the system.. What have you got to loose ?

 

https://barsleaks.com/product/liquid...tor-stop-leak/

 

Well, I went whole hog on the fix and am having a new engine put in it. I'm getting an LKQ engine with 50,000 miles on it installed and guaranteed for 1 year for $2,700. I hate to resort to letting someone else do the work but I am just not able to do this kind of repair myself.

carl

 

Wouldn't it be a bust if it overheats again due to a partially plugged radiator?
No pressure testing, no test for exhaust gas in the coolant.
No compression testing.
To much trouble!
A 2700$ gamble.
Good luck.

 

I have a leaking head gasket regardless of any other issues. Considering the mileage, the engine replacement was necessary.


carl

 

I think that was the question carl... You have CONFIRMED that the head gasket leaks ? Or is it external and visible ?

 

Yup. I confirmed it. It's leaking a fairly steady trickle.


carl

 

I would like to thread jack this thread! (was literally about to make a thread with exact title) - I'm having the same issue (2000 4.2L - over heats on hwy, cooled down when going slow).
My top radiator hose was super hot, and lower radiator hose was cool to touch (like a cool cup of coffee - after 30mins of hwy and traffic driving).
I haven't ruled out a head gasket, but given the top hose was super hot, and lower cold - that would mean the thermostat opened correct?,,,and likely a blockage in the radiator?

 

ZEN, yes, the coolant returns to the radiator through the top hose.
if the bottom is not at least 40 degrees cooler than the top but only just warm, the coolant is not flowing through the radiator.
Good luck.

 

My plan is to replace the water pump first. In taking the lower hose off, I'll flush water through the radiator, and see if it pours out the bottom to check for a clog.

I've been hearing a weird noise on startup lately I forgot to mention. It's momentary, right when it first turns over - almost sounds like a dog bark for a second. Wondering if the impeller of the pump has come loose...

 

I want to add some information to this thread in case it helps someone who does a search for the issue, etc.


When I replaced my thermostat I bought a typical auto parts store replacement part. It didn't work. The issue with the thermostat is that it has to lock into the center of the tube that bolts to the engine. The one I got just flopped around and when I tried to bolt it together, it wouldn't seal because the thermostat could not be centered in the hole. So I bought a genuine Ford thermostat and gasket and with a twist it sort of cam locks to the tube. The gasket bolt holes are also diamond shaped to keep it in place as well. Gigantic difference and made the repair pretty easy. It's like someone thought the replacement procedure through when they were designing it.


Genuine Ford parts for the win.




carl