Cooling System Fans

[Chris142]

Originally Posted By: c3po




Can someone explain this, I have never heard of such a thing. The manufacture of Stewart Water Pumps said that since there water pump did not have a provision in the pump for a heater hose outlet that a small hole had to be drilled in the thermostat for a bypass.

He also went on to say that with this small hole drilled it would keep the temps in the cylinders more uniform because there would not be a constant flow of hot coolant and then cooler coolant.


Your SBC has a built in bypass. This is why the water pump gasket has an extra hole. With this hole there is no need to drill a hole in the stat to allow a small amount of coolant to flow.

The bottom hole in this SBC WP gasket is the bypass.

In the mid 90's they did away with the bypass and went with a hose instead.

 

[c3po]

I hate too tell you this, but I went out and checked mine and that bottom hole on the gasket was sticking out, so I have no bypass.

I am glad I checked because there was a few coolant drops around the water pump, so either I have a leak or this could be where I started the car and forgot to tighten the upper radiator hose, I lost about a pint of coolant before I tightened the hose, so I will clean the area off and see if it was just spilled cooant.

 

[NYEngineer]

The bypass is only on one side. They use that gasket on both sides. It's going to hang down on the short side. I BELIEVE the bypass is on the driver's side.
You're still good with the small hole in your thermostat. It's much higher than the bypass and will bleed off air as you fill the system. The guy telling you that hole in the t stat acts as a bypass is a little optimistic. It's kinda small to really do anything. The one in the block is the one that mixes the hot and cold coolant so not to shock the system.

 

[c3po]

This gasket was on the driver's side, I did the small hole in the thermostat just in case there was any air it would not get trapped in the cooling system, or getting trapped behind the thermostat.

I realize that a tiny hole in the thermostat is really not a bypass, this car has the original head gaskets and my feeling was that any trapped air could put pressure or hot spots in the cooling system, both of these scenarios would probably be bad for the head gasket.

 

[Chris142]

The bypass hole is in the passenger side. If your car does not have a bypass then the engine is a mid 90's or newer. If it's that new it should have the later style valvecovers.

 

[c3po]

Originally Posted By: Chris142
The bypass hole is in the passenger side. If your car does not have a bypass then the engine is a mid 90's or newer. If it's that new it should have the later style valvecovers.


Chris142, this car is a 1983 Chevrolet El Camino that I bought in 1985, so this is the older small block motor with the 2 piece rear main seal.

 

[BuickGN]

Originally Posted By: OVERK1LL
A few things:

1. The 180 and 195 have no bearing on whether the car will overheat or not. This is entirely dictated by the cooling capacity of the system in place. This includes radiator size and airflow across said radiator.

2. The best way to wire an electric fan is with a thermal switch. There are two popular types: on/off at temp, and a variable controller.

The differences are basically:
-The on/off controller turns the fan on at a point you set. Then, when the coolant drops a predetermined number of degrees, the fan goes back off. The only disadvantage to this setup is the high current draw from the starting of the fan can be hard on low-current alternators.

-The variable controllers will slowly spin-up the fan and will only spin it as fast as necessary to bring the temp back down to the predetermined range. This makes them much easier on the charging system. They are also more money. A common supplier of these is DCC.

3. Flex fans are JUNK. As RPM increases, the blades flatten out, killing air flow. They make a lot of noise and are a lot worse than a clutch fan.


I've switched both my Lincoln and Mustang to electric fan setups. This was using the on/off style thermal controller from Flexalite, run through a relay due to the current draw of the fans in question; the controller is meant to handle fan current, but for Flexalite fans, not something the size of the Ford Mark VIII fan.

The relay is hooked to key-on power, so the fan shuts off when the car does if it happens to be on when you shut off the vehicle.

I set my on temp to be 185 degrees with a 180 T-stat. With the Mark VIII fan, that lead to about 15 to 30 seconds of fan run time.

I highly recommend this setup.


That's a nice setup. I ran into fuse blowing issues when both of my fans were setup to come on at the same time and this was with a 60 amp fuse.

What I did is have the passenger side fan come on, triggered by the fuel pump since I didn't want it running while the key was on, engine off, but it needs to run regardless of water temp with all the turbo exhaust plumbing on that side.

I setup the driver's side to trigger at 175 degrees (160 degree thermostat) but only with ignition hot.

So far no more blown fuses.

A friend's GN was running hot in the summer with a front mount blocking most of the ratiator. I saw the MK VII fan you mention in the junkyard and had to try it on his car. It was a little tall but after it was modified to fit, it cools about as well as my dual fan setup. Not bad for a $15 fan.