Overheating issue - I am stumped!

[KQQL IT]

I bought a high-pressure high-volume water pump they did the same thing would hold the thermostat closed

[Mattchu60]

Well, disapointting results tonight. put the Stat back in with a hole drilled in it, still overheating at the head sender. Maybe it will improve over time, not sure. I have the heater running full blast too, I can see the heater bypass hose is working when I look down into the radiator, as its pouring water in.

The water pump I got is a AC Delco professional model.

The stat is a Stant Superstat - 195 degree.

For now I am going to run it a little more without touching it, maybe its air that will work out. If no improvement I am going to try a 180 degree stat, hoping it will open sooner and get the head cooled off sooner. NOt really what I want to do but willing to try it.

[natedogg]

Dealing with the same issue with this 86 C10 that I'm working on. Just dropped in a Goodwrench 350 with new water pump, radiator, 195 thermostat, hoses and temp sending unit. Gauge was reading close to 260. Thermostat was not opening. Put in another new 195 fail safe thermostat and still ran hot! Took the stat back out and drilled a 1/8in hole in it. That helped. It still ran hot, but took longer for gauge to rise to around 260. Took the stat back out and left it out. Truck now holds at about 155 degrees. What are the odds of 2 new stats not opening? I have worked on several of these trucks and small blocks over the years and have never had this problem. I am also going to try a 180 stat and see what happens?

[rich weyand]

Originally Posted by Mattchu60

Well, disapointting results tonight. put the Stat back in with a hole drilled in it, still overheating at the head sender. Maybe it will improve over time, not sure. I have the heater running full blast too, I can see the heater bypass hose is working when I look down into the radiator, as its pouring water in.

You shouldn't have any water movement in the radiator when the thermostat is closed. Basically, the heater hoses are connected incorrectly, and you have insufficient circulation within the engine until the thermostat opens.

The bottom hose on the heater core connects to the top front of the intake manifold. The top hose from the heater core connects to the top of the water pump. This is why I asked for the pic earlier.

I think that is the problem. You are getting hot spots in the engine because you don't have the correct flow within the engine before the thermostat opens.

[Mattchu60]

I will try to get a picture, but I didnt change anything over the stock setup for the heater hose - disconnected the one from the intake when I removed the engine, hooked it back up with I re-installed. The radiator has a connection point for the coolant to flow into the radiator after it passes through the heater core.

Its like this on mine - leaves the intake near the thermostat, routed into the heater core, leaves heater core and travels to the radiator, leaves radiator and travels to the water pump. This is the stock setup from what I see.

[Dead Parrot]

My 75 is like yours. Output from the intake manifold port, through the heater, return into the radiator. If that is the flow you are talking about happening cold, then things are working as expected. There should be minimal flow from the radiator itself with the engine cold and t-stat installed.

A lot of folks assume the water pump port is an output and run from that, to the heater core, and back to the radiator, then complain of poor heat output during cold weather.

Not sure when or why GM switched from return to radiator to return to water pump.

[rich weyand]

Originally Posted by Dead Parrot

Not sure when or why GM switched from return to radiator to return to water pump.

The engine comes up to temp faster, because all of that extra water, and the heat-radiating effect of the passenger-side radiator reservoir, aren't in the loop. The engine comes up to operational temp faster, and the thermostat opens sooner, reducing the buildup of hot spots in the engine waiting for the thermostat to open.

But the OP doesn't want to do the improved routing apparently.

[Mattchu60]

been a busy day and I haven't had any chance to take pictures yet of my setup, i work two jobs and just got into the house for the day (started at 630 this morning). I'll try to get one tomorrow.

guessing part of the issue with my heat buildup is this being a new engine, its very tight and creating a lot of heat once the T-stat does open, seems to be running around 210-215 on the highway. I have a 180 T-stat coming from Rock Auto which I think may help somewhat, should open it before the temp starts soaring (thats my hope).

[wilkin250r]

Originally Posted by Dead Parrot

A lot of folks assume the water pump port is an output and run from that, to the heater core, and back to the radiator, then complain of poor heat output during cold weather.

Not sure when or why GM switched from return to radiator to return to water pump.

I believe the manual transmissions had the heater return to the water pump, while the automatic transmissions had the heater return to the radiator. At least, that's the one thing that stuck in my head from a factory hose diagram I saw years ago.

[KQQL IT]

Mine has no heater or hoses, pipe plugs in the holes.
I'd be more concerned with the gauge being accurate and thermostat opening with pressure against it.