Odd Cooling System issue

[Raoul Ross]

So, the problem continues! Replaced the coolant flow 'valve' on the intake but it still won't heat up. Water flow from the heater core into the radiator certainly was reduced to almost half what it was but using an infrared thermometer in my heated shop it still only gets to ~150. There are a couple of other things I noticed...

1. Coolant flows through the radiator immediately. Not very much but it does. I did drill an 1/8" hole through the thermostat flange to prevent an air pocket but this appears to be a little more than I would think, thermostat stuck open? I'll probably get another one, it's not easy to replace!

2. The "clutch" fan runs at engine rpms, it doesn't speed up *or* slow down by itself. Engine off it easily turns. Is this cooling the radiator too much? The owner told me it had been replaced within the last 2 years, is it defective? IIRC they usually roar at cold start and then slow down, this one doesn't do that.

Pic of the coolant flow 'valve', new one on the right. An obvious difference!

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[Ricko1966]

The thermostat regulates water temp cold,not the fan clutch,not the radiator. Cars didn't even used to have fan clutches,I believe it's more of a power saving measure. I'd be double checking my thermostat,what temp T Stat did you put in ,and verify water temp matches T Stat temp. FWIW some vehicles have eroded the cavity where the thermostat sits and water flows around the Tstat and they never get to temp in cold weather.Your heater shoukd be hotter now with the restriction though.

 

[75gmck25]

The factory setup in my '75 350 has the heater return hose to the radiator, and it definitely gushes into the radiator as soon as you start up the truck. However, with a 195 degree high flow thermostat (which also has the drilled bypass hole) I don't have any problem with getting it warm enough to make the heater very effective. My clutch fan does work, has the typical roar at startup, and then quiets down.

A Suburban should have a T fitting in the hose, and two heater cores (front and rear), so it probably does cool the engine down quite a bit from coolant running through the heater. However, it was designed to operate this way, so it should still heat up.

 

[grummy]

You know what my Dad told me once ? If you really want to know whats going on with a thermostat, you absolutely must put it in a pot of water on the kitchen stove with a thermometer in the water. Watching it carefully, when you see it open, note the temp on the thermometer. And with the quality of today's thermostats, it makes even more sense.

I wouldn't screw around anymore. I'd pull the stat, and put it on the stove. There is just no way to tell if it is working according to the marked temperature. I get the feeling its opening way early. I never had an engine I could cool with just a heater core.

 

[Raoul Ross]

Brand new NAPA 195 thermostat and yea, it does sound like it opens early or doesn't close all the way. No rear seat heater or if there is, there's no lines to it. The only reason I was thinking about the clutch fan is the fact there's coolant going through the radiator *and* the fan is pulling air through constantly.

I left it sit running outside for a good 45-60 minutes at ~20F ambient and it actually cooled down to 77F on the infrared thermometer, measured at the heater hose outlet on the intake. I'll put another thermostat in Wednesday *without* a pee-hole and see what happens.

Thanx guys for the input!

 

[mtbadbob]

Brand new NAPA 195 thermostat and yea, it does sound like it opens early or doesn't close all the way. No rear seat heater or if there is, there's no lines to it. The only reason I was thinking about the clutch fan is the fact there's coolant going through the radiator *and* the fan is pulling air through constantly.

I left it sit running outside for a good 45-60 minutes at ~20F ambient and it actually cooled down to 77F on the infrared thermometer, measured at the heater hose outlet on the intake. I'll put another thermostat in Wednesday *without* a pee-hole and see what happens.

Thanx guys for the input!

The new "Fail-safe" T-stats "fail" OPEN! My mechanic buddy is NAPA Certified Repair, but WILL NOT use their t-stats for this exact reason. A co-worker of mine was having this issue on his '89 Blazer and I told him to change the stat as I thought it was stuck open, even though he said "It's almost brand new". Anyway, he changed it, has great heat & NORMAL operating ranges on his temp guage now...

 

[mtbadbob]

BTW, I've NEVER had to drill an air hole in my stat as the air will works it's way out of the system in no time...