I've read here and elsewhere for hours and decided to post my own thread asking for help after not being able to nail down this issue...

My 2003 F150 5.4 started having issues a month or so ago where on a cold start, after running for a few minutes I would get ice cold air with the heat on. As it got to operating temp, the temp gauge would spike very quickly, coolant sprayed out of the degas reservoir, the temp needle would suddenly drop quickly back to the middle and I had heat. I would also hear a whining noise as this happened. I was topping off the coolant that was lost. I did some research and replaced the water pump and thermostat. The whining was gone (probably the water pump?) but I had the same issues. The only difference was the temp gauge wouldn't spike all the way up, just to about 3/4 of the way. I hear gurgling at idle, so I figured I had an air lock issue. I tried every suggestion to remove that and nothing seemed to work, so I took it to a buddy's shop to have a coolant flush with vacuum fill. Same issues...

Yesterday I got it to temp, watching the degas bottle fill up, squeezed the top radiator hose to burp out air. Saw that as soon as it got to temp and that needle dropped, the degas bottle emptied like a toilet flushing, sucking in air after it emptied. I assume this is when the thermostat opens up. I let it cool again and did the same thing. This time I was ready and poured in coolant as it emptied, almost a whole gallon of 50/50. Thought maybe I had prevented the air getting back in the system. Let it cool down again and then got it back up to temp. It puked out most of that gallon of coolant from the degas reservoir onto my driveway...

I was ready to give up when tonight I happened to check under my rubber floor mats and found that the carpet was wet under the passenger side mat. The cab doesn't smell of coolant, so I'm not sure if it's water or coolant. I have noticed small puddles under the truck after parking it, right about under where the heater core would be, but I've smelled and gave the liquid a quick taste and I think it's just water. I've seen that since summer and assumed it was just condensation from the A/C.

I've searched for coolant flow diagrams for this engine and haven't found anything that's very clear. Is it possible I have a plugged heater core or radiator? It's like the coolant gets backed up into the degas reservoir until the truck gets to temp and then when the thermostat opens everything starts flowing and I get heat.

The truck has 143,000 miles on it and I've done all repairs to this point myself, but this one really has me scratching my head. Any help from those with experience is greatly appreciated!

 

Have you tested the coolant for hydrocarbons /exhaust gases? Have you pressure tested the coolant system and see if any leaks can be spotted?
Have you replaced any of the coolant hoses?? They maybe de-laminating from the inside out.

 

Thanks for the suggestions. No, I haven't tested the coolant for hydrocarbons. Is a test kit something I can get at a local parts store? I'll have to look into that. I haven't tested for pressure in the coolant system either (again, lack of testing hardware), but I believe it's holding pressure since I do still get a good amount of release hiss when I open the cap after the engine has cooled down for a good amount of time. Worth checking though, I agree. Haven't replaced hoses. Any recommendations on what to start with there? Maybe those on the heater core?

FWIW, I have noticed that the temp gauge doesn't peg as high if I'm running the defroster on a cold start. Maybe with the A/C on for that it's not building up as much back pressure to the degas bottle.. I dunno.

My other daily driver is a lowered Audi A3 with summer sticky tires on it. Not ideal for Wisconsin winters, so I need to at least limp the truck through winter before I'll be able to do any major work on it where it will be in the garage for a while. I've been trying to prepare myself for the possibility of a head gasket or engine swap if needed. In the last year I've done brakes, exhaust, suspension, steering gear box, pittman and idler arm, alternator, water pump, thermostat, battery and tires on the truck. I've put too much work into it and busted too many knuckles to give up on it, and it's in great shape with almost zero rust. I fully intend to get another 100K miles out of Ol' Blue.

 

I believe O'Reilly has these kits for loan, just buy the fluid. They should also have pressure testers for loan. The pressure tester should also be able to test the cap to see if it's holding pressure and releasing at the right spec.

 

Thanks! I think I'll order that from Amazon. Seems like a good tool to add to my garage. I appreciate the advise, guys.

 

So, my hydrocarbon test kit arrived a few days ago and I finally got around to trying it out on the truck last night. The good news is my troubleshooting (with your help) is starting to lead me down a path to resolution. The bad news is the blue water turned yellow in the test kit... Yeah, I'll be shopping for a reman crate engine as I limp this thing through winter. Looks like Jegs has some good options.

 

Interesting. At least you found your issue.

Still can't believe, only 143k miles...

 

Right! Looks like the Jegs reman engines come with a 3 year warranty, though I don't know the details of that warranty yet. Maybe warranty claims are impossible if it isn't installed by someone with certain qualifications, I don't know. Perhaps that's a subject for a new thread. Anyway, I'd love to get another 100,000 out of this truck with the condition the body and interior is in.

 

Maybe new head gaskets for your current engine?

 

Maybe, but from what I've read, by the time you get to the head gasket, you may as well replace the engine. If there is a hairline crack somewhere or something, you've just done a ton of work to replace a gasket on an engine that's still broken. From what I understand, Ford shops don't bother with head gasket replacements any longer. Engines are just swapped for remanufactured ones that meet specs and are warrantied. I don't want to have to do the work twice.

I'm open to other opinions or the knowledge of others who have done this. Your thoughts?

 

Yeah, you are probably right about going for a reman engine or a new truck. $$$$$$

 

Yeah, if I can drop a reman engine in there and do the work myself for maybe $4000, I'd be happy to have a warrantied engine in a truck where I've done practically every other typical fix for its age in the last year or so. I can't find a new truck for $4000 that wouldn't be rusted out and need all the same work I've done on this one, only to fail in the same way a year down the road. It sucks to think of an engine replacement as a maintenance task before 150,000 miles, but it's probably my best option right now.

 

150k miles can be a lot or not.

Do you do a lot of city driving, idling, etc? That puts a lot of wear and tear on an engine versus 150k of all highway.