Hi,

I have a 2003 Ford Explorer XLT 4.0L. The Collant Reservoir is overflowing when the engine gets hot. I have changed the following:

• Water Pump
• Thermostat
• Coolant Cap
• Radiator

But now have fixed the issue. Any idea what could be causing this?

Thx

 

There several possibilities for this problem.
among them are, there is air trapped in the system, or cooling fan(s) not coming on when required, or possibly a head gasket allowing combustion pressure to enter the cooling system.
If you have or rent a cooling system pressure tester and pump up the pressure to no more than 15 lbs and then release the pressure if the coolant comes gushing out the radiator fill there is air trapped in the system.
With the radiator cap removed ,engine cold, start the engine and observe the coolant. If you see bubbles coming up to the filler neck , there is a good possibility compression is leaking into the cooling system which would require further testing to determine whether a head gasket problem exists.
Let us know what you find.

 

Thanks for the help. I'll try your suggestions.

 

My best guess after reading all that you have done, do a compression check, and a leak down check, maybe the heads are leaking. Do a radiator pressure check. Burp the cooling system. Don't fill the overflow bottle up past the 'hot' mark when hot. Stuck Thermostat? Hole up?

As Jaguar says in their owners manual for the double six's, "Any coolant temperature is fine, as long as no coolant is lost." But these are the same folks who also said to take the Jaguar up to a three digit speed limit once a month.

skip.

 

you could have a radiator cap getting weak, or the rubber seal or gasket in the cap has gone bad

 

Thanks. I replaced the cap. I suspect the head is cracked or a blown gasket. I'll have to do a compression check to know.