I have a '97, 4.0L, automatic, 4x4 Ranger.

I was driving up a mountain road with quite a load in the back. I pulled over as soon as I saw the temperature guage start to climb and when I came to a stop, coolant was spewing everywhere. I had the truck towed to the closest garage. The frost plug had actually blown out. They replaced the block heater and frost plug and no coolant seemed to leak from anywhere. They took it for a test drive and as soon as the truck warms up, hot coolant just blows the cap off the reservoir and spews all over. They thought the thermostat might be stuck so replaced that as well, the same thing still happens. They also installed t-valves in the hoses to bleed out any air that might be in the system but this didn't help either.

Any ideas what else could be causing this to happen?
Thanks.

 

Have the garage check for exhaust gas in the coolant. Could be a blown head gasket pressuring the cooling system beyond the 15-17 psi cap limit.

 

Leave the cap off the radiator, warm it up, and let the coolant level stabilize. Some will spill along the way as it's warming up. Look for bubbles/foam in the coolant once it's warmed up. Cross your fingers that you don't see bubbles/foam which implies head gasket or cracked head.

 

They did do that. It was bubbling in the reservoir until they bled out the system. It stopped bubbling after that but when they took it for a test drive it blew the cap off again. They have it apart now and are sending the heads to a machine shop to be tested. They said they didn't see anything horrible, no obvious cracks or anything, but I don't really know what that means in the long run. If there aren't any cracks, does that mean that it was a lot of extra shop labour for nothing? If it still does it when they put it back together, what then?

 

Actually, testing the heads for cracks is sound practice, don't consider it money wasted even if they come back OK. If the heads do check out OK, or even if you have to install new heads, that should mean new headgaskets, as well.

 

Thanks. I'll let you guys know how it turns out.

 

So it turns out that one of the heads was cracked and is not repaireable, and the other one is repairable (I don't know if it actually cracked or just warped). It's been ten days now and I am still witing to hear when it will be fixed and how much it will cost me! As soon as I get it back, I have a 1000 more km's to drive to get to my destination. Do I have to drive easier with the new heads for a while or just drive normally?

 

Change the radiator to a larger size such as a 3 row like I did on my 88 ranger V6. What a bunch of cheap Ford is about thier cooling systems. They are so stupid they can't figure out why they have so many head gasket and other cooling related issues.

 

I would just drive it normally and follow up with an oil change 500 miles after service (sounds like at your destination). This will provide piece of mind that any debris is removed. And yes, in order to inspect for head damage and a blown head gasket there was no choice but to tear into it; they are not scamming you.

Are they doing a valve job since they've got it all apart now?