ZZ502 Engine Cooling Help

[Woj]

Hi Folks,

I've got a 502 crate engine in my 69 Post Chevelle (Resto Mod) with an mechanical water pump and electric cooling fans. When I bought the car about 8 years ago, the cooling system worked ok, but it could get fairly hot on a warm day. Long story short, the cooling fans, electric fuel pump and ignition were on the same 20 amp circuit that eventually fried itself out and the car no longer ran.

A good friend rewired the circuit and put the cooling fans and fuel pump on a separate high-amp circuit. Everything worked great. However, the cooling fans worked too much due to a low temp switch. The engine was running cool (140 degrees). I went to replace the thermostat only to find out the one in there was rigged to full open.

Chevrolet recommends a 180 degree thermostat which is what I put in. I also changed the temp switch for the cooling fans to one that comes on at 200 and shuts off at 180. Unfortunately I could not get the fans to come back on.

Here's where my real question comes in. The temp switch for the cooling fans is in the intake manifold, with the thermostat at 180, should I get a switch that turns the fans on cooler than 180 or greater than 180? I currently have the 200 degree switch that did not turn on the fans. I did not test the switch to be completely accurate, but it is brand new.

I thought ideally, I'd have a temp switch in the radiator (like newer cars), but the only fitting I could put one in there is near the top and if the coolant is low I don't think I'd get a good reading for it to work.

I'd appreciate any thoughts from anyone that has gone down this road before.

Phil Woj.

[Lynn]

Seems lately that quality control on auto parts (at least for me) has been a crap shoot.
Just a few examples; brand new Tstat that would not open properly, mechanical fuel pumps (multiple) with WAY too high pressure, pressure sending switches that made the gauge read way low, and a temp sender that made the gauge read low.

All in the last three years.

First lesson, don't trust anything without testing it these days. I would test that switch in the kitchen, in had water using an accurate cooking thermometer.

With all of that being said, in the cold winter temps, the engine temp may not be exceeding 180. Also, just because the Tstat is rated 180, doesn't mean it isn't opening at 175 or there abouts. If you are driving around (with air moving throught the radiator) in frigid temps, you may not be exceedng 180, let alone the 200 needed to start the fans; the electric fans will not kick on at all.

If you are sitting idling, I would think the temp would eventually start to climb. Watch your temp gauge.

[Woj]

I did have the car idling for quite some time with outside air temp around 65 degrees. The temp gage in the car was saying 210 degrees, my laser thermometer was saying 185 at the thermostat housing. I will do a test on the kitchen stove to see if the temp switch even works at all. Phil

[SuperNovaSS]

Since it is new wiring, have you tried grounding out the sender wire to see if the fans come on then?

Jason

[Woj]

Since it is new wiring, have you tried grounding out the sender wire to see if the fans come on then?

Jason

Yes, grounding the fan relay wire started the fans right up. Cooled the system down quickly.

Still exploring.

[L_e_e]

By any chance was it a crate engine that was originally designed to run a serpentine belt and you are running a V-belt set up? if so, then the water pump has a reverse flow impeller.

[Woj]

Great question Lee. It is running on a serpentine belt. Let me check the rotation tomorrow.
Thanks Jim for the clue on this one.
Phil

[iluv69s]

I would check any thermostat before installing. Many junk parts out there now. Easy to do by putting in water on the stove with a thermometer.

[L_e_e]

With your current serpentine set up does the water pump spin CW or CCW?
If CCW it needs a reverse pump, CW needs a standard pump.

[Woj]

Well, I had some time and did some work on the car today. I did a boiling-water-stove-test of the thermal switch for the fans, it worked, although it is supposed to come on at 200 degrees F, it did so at 210 degrees. It did stay on until about 195 degrees. I changed the location of that switch to the cylinder head and the gage temp sender returned to the intake manifold. Ran the car and it all worked. Using a laser thermometer the intake manifold never went over 170 degrees, even though the inside temp gage said 210 degrees.

The water pump does turn clockwise, so that is good. A new consideration for me. I think I'm going to dial back the fan thermal switch to around 180 and put in a 170 thermostat just to keep things a little cooler. I will also bench test the gage temp sender to see how accurate that is. I think it is off about 30-40 degrees, but will find out.

Thanks to all who responded here. I had a long talk with Shaun (Galveston) and he helped quite a bit with some of the considerations on temperatures and sending units.

It is off to the Phoenix auctions tomorrow, hope to see a few of the SYC guys out there.

Thanks again for all the input.

Phil W.