On my EA81 transplanted '78 Brat, I was wondering what should be the proper operating temp? On the highway the temp gauge stays right near the lower dash mark. During idling or stop and go traffic the temp fluctuates quite a bit. Usually midway or closer to the top dash mark. I replaced the thermostat with an OEM. Replaced the themoswitch with a aftermarket four seasons 35942. Replaced the radiator cap with a 13lb aftermarket. I also tried another used temp sending unit I had laying around. The electric fan does kick on when the temp gauge gets close to the top dash mark right below "H" but shuts off again at about midway between the upper and lower dashes. Is this normal? I could be wrong, but I think I recall that my brat would always be around the lower dash mark, regardless of highway speeds, stop and go, or just idling. Some help please!! Maybe I'm just going crazy here.

Thanks,

-Steve in Denver

You are right, it shouldn't go that high at all. Sounds like the fan isn't kicking on and staying on when it needs to.

Yes, that's what I think too. Is it possible that I have two bad aftermarket thermo switches? I checked my local Subaru parts counter and they told me that a factory switch is no longer available. Anyone seen or heard anything like this? It's got me and a few people I know stumped.

I agree with Shawn; it doesn't sound right. But perhaps, it's just mis-reading the temp. On cars as old as ours, ground connections tend to go bad and that might be the issue here. Firstly, try to borrow one of those infra-red optical thermometers and measure the actual temp of the radiator when the fan turns on and off. If the temps are in a normal range, around 180 to 200, then you know the temp gauge is lying to you and you have to correct that. If it is truly overheating, then you need to address that problem.

the older rads had thermo switch low in rad it likes to acumulate crap at bottom of rad and tends to bypass switch check that your rad is getting hot at lower half make shure 195 tremostat and put a 7 psi rad cap theese syestems do not like high preshure rad caps. Should have some room for expanding in rad about 2 inchs from top fan should come on just above half and run for no more than 2 minutes max.

u can use a loyale rad switch get it to turn on a realy that turns on fan thiss will take load of the switch and make it last longer and fan will run faster and stronger

Ivans, Crap at the bottom of the radiator. that sounds most logical at this point. Should I try a garden hose radiator/cooling system flush? I know there is a radiator drain plug below the thermo switch.

Edrach, I have a spare instrument cluster I can try to see if its the gauge itself.

Also make sure the ground wire on the edge of the radiator support is screwed into the radiator itself too. These break very often on the 80-84 and I bet a 78 has them too.

Edrach,

 

Yup you got it. Bad gauge. Wow, so frustrating.. Swapped instrument clusters and everything is normal. Thanks for the help everyone. Hopefully this thread will help the next guy.