bhines1977

Hello,
I have a 97 f150 4.6 that has no heat. I have searched forums numerous times and nothing has worked. For starters I have replaced tstat 170°, water pump, radiator cap. I have flushed the system upside down inside out. Yes the heater core was flushed separately. Has a flush kit installed. I replaced the cap cause the system is not get any pressure. I can run truck for hrs and pull the cap off. I am not loosing antifreeze. I made sure the block was full of fluid when I installed the tstat. Im at a stand still here. Any help would be great!

Also could the lines on the heater core be switched? Im getting good flow both ways when flushing with water and air.

I did add antifreeze in the flush kit cap to try and get all air out of system.

kmjwing

I had the same thing happen on my 98 4.6 twice. Just for kicks smell the anti freeze off the cap or tank if it smells a little bit like fuel is a head gasket. Mine blew between 3 and 4 cylinders I think. It also never dropped a bit of coolant but my #4 plug was blasted clean from the leak. That would explain the no pressure situation and the no heat situations that I had. Does your truck have any coolant leaks? You have to make sure the system is tight for it to work right. The second time it was the heater core plugged up no heat but system had pressure. I changed it tore the dash apart not the easiest thing to change but I had to have heat in the winter time. It's was like a two day event I never want to do it again. Hope this helps. It's just my experience and by the way I sold it last March to a friend with 260000 miles and it's still going strong

bhines1977

I will check all the plugs again. Just changed them about a month ago cause of a miss. Is the head gasket a task the normal shade tree guy should take on? Thanks for the reply.

JCR 56

The OEM thermostat is 192*. 170* is way too cool.

kmjwing

Yep I had a miss too it took care of it for a little bit but eventually I had a wet plug from the head gasket. I unfortunetly didn't do the head gasket myself because of time and it was winter at like a constant below zero winter. I looked in a maintenance book on how to change it and it didn't look too bad I thought it was a little easier than a conventional push rod engine. If I was you I would pick the brains of a few more people and do some more troubleshooting just to be dame sure it's a head gasket so your not changing it just for the hell of it. But just one word of advice if you do take it on when you have the top end off there is a little cheesy coolant transfer tube under the intake change that because it's a known leaker. Hope this helps let me know how u fair out

bhines1977

Update!
I tested the pressure on the cooling system. Held 16lbs pressure for 10min no drop. So I flushed the system again. It wasnt horrible but still brown. Filled with water and no tstat. Added some bars coolant flush drove about 20 miles. Reflushed everything. Slowly refilled system through the heater core hose. Also filled radiator through the overflow. Installed a 195 tstat. Squeezed to hose to get more air out. Test drive and my heater is blowing hot 130°. Good pressure on top hose.

Now for the bad. It has a bad miss. It has done this before. I think I got water on top of plugs. Going to replace all plugs again today. Hopefully that takes care of the miss and the pressure in system isnt blowing by head gasket. I will update again when im done. Unless I find a jeep before. Lol thanks for the help and the awesome web page!

bhines1977

All right! Went to auto zoo and had the code read. Misfire in 4 and 8 cyl. So I decided to clean them instead of replace. Mainly cause the guy at auto zoo decided the guy behind me was more important. Anyhow its running great and I have heat. Plug wires was still wet even after blowing them out with air. Fingers crossed but I think I finally whooped this one! Heck I even got the spongy brakes fixed while I was at it. Now for the key dinger. Thanks for all the help.

kmjwing

Sweet sounds great. How did u fix the brakes I fought that for years never could get it right. A real hair puller.

bhines1977

Ok I lied. Heat isnt blowing hot anymore. Its warm barely. Im so lost. Runs great now! Could it be the fan not letting the engine warm up enough? I did notice the lower hose was warm and top was hot. That would mean the radiator is cooling good I guess? I guess it could be an air pocket in heater core. Anyone have anymore guesses? Thanks for any idea?

On the firewall I pulled the master cyl off and unscrewed the push bolt about a turn and a half. Works good now!

kmjwing

No way on the brakes I wish I would have thought of that I did replace the master cylinder but it didn't help. Yea in kinda wondering about ur heat issue. I know on mine I did start out with a fan heat resistor on the fan. It wasn't having output on fan settings low and medium but it did have it on high so that drove me to that resistor. Maybe you do have heat but ur not getting it to the cab with the fan. That's also the problem I had too. The check for that is turn the fan on you won't hear the fan come on in those two lower settings but it will in the high setting. And also another system to check is the blend door but that's usually when you don't have control of the temp. But maybe it's stuck in the closed position which won't give you heat. I'm not sure on the check out how to check the blend door operation but I know it can be ops checked you have to look that up online or on the forum here somewhere else. Try that out just to narrow it down I guess. Sorry it took me a little bit to check back. I petty curious with what you have goin on because it was just like my old truck. Anyway let me know.