I have a '97 Expy xlt 2wd 4.6 motor 160k miles. Have had a overheat- no heat- limp mode problem for about a couple weeks now. I have changed 2 thermostats, water pump, temp sensor, temp sender, threw a 1299 code so I changed the cylinder overtemp protect sensor and changed the heater core over the summer when I did the blend door. Only happens intermitantly and when the temp. needle pegs and goes into limp mode I stop turn it off for a minute start it back up and I get heat, no overheating and the truck runs fine, no issues at all. Finally gave up and took it to the dealer. After 5 days of them looking at it they can't find the problem so they said the motor was no good internally. They gave me no concrete answer, said I have a cracked block, cracked head, bad head gasket or a blocked port. I found a 2000 4.6 with only 90 k on it. My question is are the block and heads the same as the '97? I am using all my electronics I am just going to use the long block.

Thanks in advance, Bernie

 

Replace the water pump, it's likely the impeller broke loose from the shaft. Sometimes it grabs and pumps coolant, and other times it spins free and doesn't pump coolant.

 

Here, read this thread and take a look at the picture in post #6. This is likely what happened with yours.
https://www.ford-trucks.com/forums/1...-cold-air.html

 

Thanks Alloro for the quick response. I replaced the water pump last Saturday as a last effort before the dealer. I am getting mass pressure in the entire coolant system. But is Ice cold. Any idea on if the long blocks are the same from a 97' to a 2000?
Thanks,
Bernie

 

Oops sorry about that. I missed that you replaced the WP in your first post. If the coolant system is pressurizing then that can be a blown head gasket.

 

The head gasket is exactly what I was thinking. The motor is getting up there in miles and after picking it up at the dealer today it seems to be making some weird noises and was blowing coolant out the cap. Just drove it now a couple hours later and it seems to be running fine with just luke warm heat. Would a head gasket or cracked block/head cause this crazy hot cold engine situation? No heat, crazy pressure and cold hoses after running for a good half hour. I felt the intake and it's not even hot. I think the PO used about a gallon of bars stop leak to stop a leaky freeze plug. There is a huge rock hard line coming out of one of the freeze plugs. Motor on top of everything else is probably clogged up. I am afraid of doing the HG and the problem still is there cause of a clog. The lower mile engine is looking better all the time. It will be good to get my 2 boys 13 and14 into their first engine R&R.
Thanks again,
Bernie

 

Yes because the compression from the cylinder creates air pockets in the cooling system and those air pockets are what's giving the erratic behavior.

 

I am going to do head gaskets first. Once I get it apart I'll know for sure. The motor is coming out cause those freeze plugs need to be changed. Done a lot easier on a stand than under the truck. Going to keep driving till thanksgiving. I'll have 4 days off to rip. Into it
Rather keep what I have and know. You never know about junkyard motors.
Bernier

 

You might first want to do a compression test to confirm it's a blown head gasket. I'd hate for you to rip it apart only to find the problem is something else and you don't have what you need to reassemble it.

 

I'll do a comp. test probably tomorrow to make sure. Today I took it on the highway and had gotten only to 50 mph and so much pressure built up in the coolant system it blew a relatively new heater hose. A s soon as I pull the right plug I should be able to see if it was burnt coolant. Happened pretty far from home so I limped it home stopping quite often for a cool down. There is defiantly something going on with the pressure in the coolant system though. Would a clogged port from all that bars stopleak cause that much pressure? or was it from going on the highway at faster rpms, more pressure. Well after the comp. test the motors coming out. I now have a thanksgiving day project.


Bernie

 

A clogged radiator will give pretty much the same symptoms, but a compression test will let you know one way or the other.

 

I noticed last weekend when I did the water pump that some of the coils were separating from the core on the rad.. Probably original rad.. The other owner was an old man in Arizona. The truck is rust free and I think is worth the money to fix. I'll put new rad. on the list as well.
Thanks for all your help,
Bernie