This is a side issue to my thread about my cracked head/block blown head gasket.


After flushing the cooling system, including flushing the heater core in both directions, I was running the engine to see if a sticking thermostat had been the cause of my sudden overheating. I was running it with no thermostat.

I noticed that both heater hoses stayed cold. They did get warm close to the engine, but not back by the firewall, and I was getting no heat from the vents. This suggests there was no flow.

Is the restriction of the thermostat necessary to get flow to go through the heater core?

 

I don't think so.

Water pump impeller?

 

Hmmmm. Might be part of the overall problem, but the water does circulate well through the radiator.

 

What were your outdoor temps at the time and how long did the engine run?

 

50s. Ran for a half hour. The radiator hoses were hot. Temps on the gauge hovered one notch above 210.

Plenty of heat to warm up the heater core.

 

Even though your getting good circulation in the radiator cruisers point about the pump could be worth considering. I take it you've got no HCV?

 

Nope. It's a 97. Just hoses. Why one is a 5/8" and one is a 3/4" is a mystery for the ages....

If I had not run water through it both ways with the garden hose I would just assume it's clogged up, but... I did flow plenty, both ways, and then blew it out with air afterwards. There doesn't seem to be any restriction.

I think once I find out how much trouble I'm in with my engine (assuming it's the head or gasket) I'll just pop a new pump in there for giggles. I have new hoses ready to go, so I might as well do the whole job.

At the moment I'm off to NAPA for a 12 point deep well socket for those head bolts!

 

Sounds like a pump issue IMO but tear the damn thing apart already I want to see some karnage

 

Just thought of something. What about a blockage in the inlet tube?

 

Good thought, Earl. I flushed it by disconnecting both hoses at the front end and hooking the garden hose to each in turn, so that wouldn't have cleared the inlet tube.

I'll check that in the morning!

 

You've got air trapped in the heater core. It's not allowing coolant flow. Try it again but don't blow it out with air next time. Worth a shot.

 

The blowing with air came after the non-flow condition.

 

Well, I checked the inlet pipe today. It's clear. Either the thermostat is needed to produce enough restriction so that some will be redirected to the heater core, or the water pump is shot.

I'll be pulling the water pump tomorrow!

 

I had the same problem with my 91. After I removed the HCV and installed new hoses, the heater would warm up, but not heat. So I flushed the heater core like you did, water hose and air hose. When I got ready to fill the system I used the heater hose off the thermostat housing. I put my funnel in the hose and filled till coolant came out the radiator fill neck. I put the cap on the radiator then filled till it came out the heater hose fitting on the thermostat housing. I put the heater hose back on and I have heat in the cab just like it should be.

 

That sounds like good advice.