Hello all my first post here. Just acquired a '66 C10 with the L6 250 and having heater problems. It appears I'm not getting water flow through the core as evidenced by lack of heat generated and core intake plumbing is cold after engine is up to temp. Wandering if I may have a water pump problem. Here's what I've done so far: 1. Replaced heater motor & squirrel cage. Original motor was frozen up. 2. Cleaned air flow ducting to & from heater core. 3. Flushed core with clean water. A lot of sludge was removed but water flow was immediate. No blockage. Temps here in Michigan have been rather cool and longest drive so far has been 30 minutes. If the water pump was inop I believe I'd get an engine idiot light(if working) and/or coolant overflow. The radiator is normally hot to the touch, so I think there's flow between the radiator and through the engine. Haven't checked hoses for blockage, but will before tackling the pump. Stumped so far... Thx 66FLWB
Welcome to the forum, Sounds very much like a plugged up hose and not your waterpump. Easy way to tell is to remove the hose at the firewall and fire up the engine. If you don't have water squirting at you, you've got a plugged hose. Honestly, if it were a problem with the waterpump, it is usually accompanied by loud rattling noises from the pump. If the vehicle has sat for any length of time, the water and crud tend to rust up and clog the hoses. It only takes a small bit of this to clog up the entrance to the heater core since the tubing in it is quite smaller than the heater hose. Hope this helps, Dr Mike
Dr. Mike, Thanks for the welcome and troubleshooting info. Agreed that the pump is fine. Pulled & checked the thermostat and confirmed it's working properly. The radiator has no cold spots and radiator hose differential temps appear normal to the touch. I'll try your hose disconnect next. We're down to that or the heater core which is on order. I haven't checked core plumbing design to determine if it's one line running through fins or if it's similar to the radiator, multiple flow routes. If it's the later, water could be bypassing the majority of the core. Thanks again... 66FLWB
Plugged hoses were the culprit. As Dr. Mike suggested the heater hoses were disconnected at core and engine run. There was no flow until also loosening hoses at the engine. Replaced the hoses and there's plenty of heat now. Flushed core again as it was readily accessible with little debris noted. After reassembly the system was pressure flushed twice and still noted rusty water and some sludge. Will have to keep an eye on the core and radiator for deterioration. Will be putting the truck up for winter storage shortly and plan to flush coolant system again in the spring. Thanks... 66FLWB
Glad to hear that was the problem and not the heater core. They can get expensive. Keep the thing flushed out every once in a while and it will keep working fine for you. Mike
Charles F Rising JR: most radiator repair shops recomend changeing the antifreeze once a year at the least as it will void any rad warrenties if rust is in the cooling system a good winterizing antifreeze is good for storage in the winter.one that wont freeze up and turn to sludge is what i am talking about . i work in a rad repair shop.
