NO HEAT and I'm at a loss ****HELP****

NO HEAT and I'm at a loss ****UPDATED w/more HEAT!!****

I used my 92' DD51T during Halloween to cart trick-or-treaters around and had a nice warm cab to ride in. At that point heat was working fine....almost too well. Fast forward about 3 weeks later, I get in and start the mini for the first time since Halloween and NO HEAT. The blower is blowing ambient temperature air.

There was a broken wire that plugs into an electrical connection on top of the thermostat. I repaired the wire and plugged it back in and no improvement. The large hose running to the thermostat on top of the engine is hot to touch. The small hose (return line?) is also hot to touch. I pulled the dash off and all the switches for the HVAC are all intact and working fine. The heater fuse under the drivers side dash is fine. The truck reaches operating temperature and the electric radiator fan kicks on fine.

So I crawled under the front end of the truck and touched the hoses that come from the radiator. There are 2 large hoses and 2 small hoses. The large and small hoses that run to the thermostat are hot to touch. The other large and small hose is not at all hot. I'm assuming this is the hose that runs to the heater core and the return line, but I'm guessing here. I know the larger hose comes off the bottom of the radiator.

Can somebody give me a suggestion here? Should I pull the hoses off to make sure the heater core isn't clogged up, or the hoses aren't clogged up? What could be the problem and where do I go for here?

Help please.:frustration:

 

Might have to remove the hoses see if they are plugged up and clean them out. Flush out the heater core. Ive had several trucks where the radiators lines have been stopped up with gooooo. Most of the time it will be the lines for the preheat for carb.

 

Thanks Trax for the suggestion. I'll remove them tomorrow and give everything a flush if there's goo or debris.

 

You probably already know this but if you have the blower setting on where it's just blowing on your face (dash) it won't blow out heat. Try switching it to vent (windshield) setting and see what you get then.

 

I appreciate the advice. I found that info reading through old threads. I almost always keep the heater on defrost when I run it.

 

Also make sure the cut off valve (which moves with the heat selector knob) is actually opening up when you go from hot to cold. sometimes the plastic arm breaks, or the cable snaps.

 

Will do Don. At a glance the cable looked good, but I'll have to inspect it closer tomorrow. Thanks you guys for your help. Keep it coming.

 

So this afternoon I pulled off the hoses and washed everything out with a water hose. There was a LOT of rust and crud in the coolant system. I did the best I could to flush the system with a hose, but I believe there's still a lot of crud remaining. It could use a thorough flush.

So I buttoned everything back up and filled the radiator with fresh water. Started the truck and it came up to operating temp very quickly. When I touched the radiator hoses (that felt hot yesterday) they were cold. So at this point I think the water pump is toast, or the thermostat is plugged up. The temp gauge came up quicker than normal and the engine started to have that hot smell.

Unless anyone can suggest anything to the contrary I'm going to be ordering a new water thermostat. If that doesn't work the next step will be a new water pump.

Thanks guys.

 

Get the front end up higher(ramps if you have them)than the engine. Start the engine with heater in the hot position and let it run, leave radiator cap off, keeping a eye on the temp. Fill the radiator up to the top and let it come up to temp. If any air in system it will work its shelf out. If it doesnt maybe the thermostat is bad. Might try it with out thermostat and or take thermostat out and put it in boiling water and see if its working.
Ive had several trucks that I thought had a bad thermostat and it was only air in the system. Got to bleed the system.
Some models have a bleed screw(8mm) on top of the thermostat housing, play with it a little if it has one.

 

What yr, is truck and how many kms?

 

I'm glad to get all this advice. I will try to bleed the air this afternoon.

It's a 1992 DD51T with 65,000k.

 

isnt running hot is it?

 

Nossir. Normal operating temperature. The radiator fan is functioning normal too.

I got it put back together, elevated it on my ramps, and filled with 50/50 antifreeze. I believe there's still a fair amount of air in the coolant system though. I'm planning on elevating it again and trying to purge the air a little better.

At this point still no heat in the cab. I sincerely hope that it's just air locked and I can remedy the no heat problem with a proper purge of the system.

eta: HAPPY THANKSGIVING to you guys.

 

Also, elevate it backwards with the rad cap on. (Rear end up in the air) Helps get bubbles out of the heater core. Then back to having the front end up with rad cap off.

Your truck does have the bleed screw. You can use that method.

I also pump the hoses by hand to have some additional force on the fluid. Sounds like just an air bubble. They can sometimes be buggers to get out.

 

The wife has put me to the task of doing Christmas lights this morning. So I'll tilt the truck back and forth this afternoon and try to bleed out all the air. I'll update the thread ASAP.

Thank you guys for helping out a newb that's still trying to learn about these trucks as I go. I genuinely appreciate all the good intel.

 

HOT DOG fellas I have heat.

After flushing out the entire system I must have entrained a big air bubble up in the heater core. I elevated the front then the rear of the truck on ramps as suggested, and opened the bleed screw on the top of the thermostat. A big glut of air came out and when fluid gushed out of the bleed screw I tightened it back down. When the truck came up to operating temp I had heat again~!!

Thank you guys for your advice!

 

Its alive I say, Its ALIVE!

 

Happy ending are always good