99 f-150 no heat

Hello, I have a 99 f-150 and I can't get any heat from it ...I have flushed out the core and still nothing. While yesterday it got hot and blew off the upper Rad. hose, I re-filled the rad. and started back up and had heat then. Then on the way home I floored it and the temp. gauge started rising and it blew the hose again!...What the heck is happening? Air locks? head gasket? any suggestions? Thanks

 

I dont think the hose should blow off. Any pressure should vent out the overflow resovoir...

What color is the oil?

What color is the antifreeze???

You changed the t stat?

 

Have you changed the rad cap and/or flushed the rad ?

 

Are you sure you bled all the air out of the system? Are you losing coolant? Does your exhaust have a sweet smell to it?

 

I am not sure how to bleed the air from the system...the hose blew off prolly because it was the spring type clamp, the cap is 16 lbs. seems a lot...I just don't get it, there is some flow thru the core but it is not flowing freely, I am considering another flush. I have put a different stat.. I tried to get it to heat up yesterday by flooring it but couldn't get it to overheat again??? I had heard some mention of blown head gasket but there doesn't seem to be any in oil or any loss... the blend door is also functioning or it seems to be...I can hear it moving. The guy I bought it from had mentioned he couldn't get the heat to work.... don't know what he tried.

 

The exhaust doesn't seem smelly but the anti freeze sure stinks.

 

When you flushed the heater core, did you do it backwards? Stuff, especially Radiator Stop Leak, will lodge itself in the core and won't pass through. Backwashing from the outlet to the inlet with a garden hose may dislodge crud. With bad smelling antifreeze, you may have other problems. Most thermostats have a hole in them to help self bleed, but it is small so it has to do it slowly.

 

I used to have to loosen up one of the heater hoses to get the last bit of air out of the system. Is the rad full of bugs, and dirt?
Sid

 

Did you check to be sure the temp valve is operating properly? Turn it in the full hot position and be sure the valve located in the engine bay opens fully. Sometimes they get stuck or the cable breaks. If you don't see a bleeder screw near the upper hose, you can bleed the air by leaving the radiator cap off (make sure engine is cool first) and squeeze upper hose repeatedly while the engine is running until no more bubbles are seen at the radiator neck. Another tip, do not flush your coolant system with cold water (garden hose) while the engine is hot!

 

You most likely have a vacuum actuated valve like in the pic below. This type of valve needs vacuum on it's port to allow hot water to flow into the heater core.

 

Regarding overheating ------

As already mentioned start with the basics first -- check the rad for buildup of debris especially if there is an A/C condensor.

That 16 psi rad cap sounds about right but it's important that it works well. The reservoir level should change between a hot and cold engine.

Is the cooling fan or clutch working properly ?

Has the rad been flushed ?

Water pump?

If your coolant level is constantly low without any signs of leaks then that would be a sign to check for leaking head/intake gasket.

 

I would do what these guys have told you. But when I used to work on cars If you had a bad head gasket the complaint was heater don't work, gets hot sometimes and I cant seem to get the air bled out.

 

nothing like this in the hoses in engine compartment, maybe in the dash area inside but I don't think so, I believe coolant travels thru the core continuously...

 

That's good news

I believe this is the part you have ("A/C Blend Door Actuator"). It's electronically controlled and located under the passenger's side dash. Check to see if it is operating properly. You should be able to hear it working when you move the temperature knob. If you don't hear anything, I would remove it and test it again. If the white shaft doesn't move, that could be your problem. You may have just had a bad actuator all along and the overheating may have been caused by air in the system after you did your flush. You said you couldn't get it to overheat again, so that is potentially a good sign. Hopefully all you have to do is replace this part. If you have bled all the air out of the cooling system and the engine is still overheating, then you likely have bigger problems.

99 F150 SCAB Blend Door Actuator/Motor - F150online Forums




Sorry, I just realized you said you already checked the blend door. Just because it is making noise, doesn't mean it is working though. Can you hear the actual door open and close or just the buzzing noise of the actuator? I would pull it out and be sure the shaft is moving. Better yet, feel the inlet and outlet hoses from the heater core and ensure both are getting hot. If not, you have a blockage in the core or the door that the actuator opens/closes is broken (as was the case with the F-150 owner in the link I sent you).

 

Check out this link to. Seems like a pretty common problem:

1999 f150 xlt no heat - F150online Forums

 

well I clamped a garden hose on to the heater hoses and backflushed the core for about 15 minutes initially it came out pretty good but I left it on anyways...I reconnected it and I had heat so I drained the water that I had in the engine and radiator and refilled with anti freeze and the heat is very minimal again, it is either air locked or the core is plugged...I will keep at it.. it is not the blend door I can hear it open and shut and the air temp. goes from cool to cold

 

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It's possible that it isn't opening/closing fully though. I had a similar problem on a Toyota I owned a few years ago. It would only open about 3/4 of the way, and once I manually forced it open I got my full heat back. Have you had any more problems with the engine overheating? Is the hose leading into the heater core getting hot? If so, and the outlet hose is not, then it's the core and or the door. Remove the actuator and try to force it all the way open by hand.

 

Ok here is another thing...when I rev the engine the hose going in to the core gets hard and I can feel pressure build up to the point I can't collapse by hand...it must be the core but it still seems funny that it works sometimes and not other times , maybe there is solids that keep finding their way back into the core veins restricting the flow.

 

Sounds like some sort of blockage, but again, it could be the blend door not opening all the way. I would remove the actuator and open the blend door manually by hand to rule that out.