Runs a little hot with heater off

[70spider]

I have developed an odd issue, when I close the heater valve the engine begins to run a little hot (195 to 200). With the valve open in runs nice and cool 185 to 190. I just replaced my heater valve and had a bit of a trouble getting the system all tightened up and leak free. I burped it by jacking the front end up and using a leak-free funnel running it for 2 fan cycles. The cooling system is all new, radiator, pump, hoses, and thermostat (190deg.) so I am perplexed. Maybe I put the hoses to the heater on backwards (the hose to the valve is connected to the line running to the water pump and the other is going to the head)? Oh, by the way I have a 1438 which has the thermostat in the block not the T set-up (should I convert it to the external thermostat set-up?). Also, another odd thing when I run the lights at night the temp gauge goes up 5 deg is this a bad ground? Thanks Pesto

[wizard124]

Sounds fine to me.

I can't speak to the temp drop when the lights are switched on. Maybe the current thru that circuit is creating a field which influences the current in the temp gage wiring. Like an electrical current affects a compass when placed too close.

[azruss]

my gage goes up a little when my lights are on as well. I assume the ground isnt great. I never tried to fix mine, just notated the change. turning on the heater is like adding a 2nd radiator, so i'm not surprised it runs a little cooler. Since you changed the stat, its not a big surprise to see a change. If you are concerned, put the old stat back in for comparison.

[70spider]

The previous thermostat was one of those "fail-safe" ones that failed, so I put in a Stant standard one. I have been reading about the problem and figure the fix may be putting a "hi-flo" thermostat in. My future plans for the car are to replace the 1438 with a 1608 so I was wondering would it be a good idea to change my cooling system to an external thermostat?

[GeorgeT]

I have developed an odd issue, when I close the heater valve the engine begins to run a little hot (195 to 200). With the valve open in runs nice and cool 185 to 190.

Not unusual, the heater core is essentially a radiator which assists in "cooling" when coolant is passing through, transferring heat from the motor to the car interior.

[azruss]

Opinions vary on the external stat. The advantage is it allows coolant to circulate through the head while the stat is closed thus reducing hot spots. The disadvantage is it is more expensive and it wants to trap air in the lower radiator hose, so it is a bigger deal getting all the air out of the system.

[carl]

I would leave the in-head thermostat in place. I converted both of my 2L spiders to in-head as it's a cleaner setup and less prone to form airpockets. As noted by others, the heater and headlight issue are fairly normal.

carl

[bobplyler]

A little trick.

If the car is starting to overheat, you can turn on the heater full blast.

[70spider]

Well for good measure I tried to burp the system again, it helped a little, runs a little cooler. I ordered a hi-flo thermostat with the correct temp (195), it so happens that the one in him now is a 180. Thanks for all your input, especially about the choice between an external or internal thermostat set-up. Pesto