My car seems to run too cool. I have a 180° Robert Shaw thermostat in it but the engine will only get to 160-170°. And that's on a 90 plus degree day. The only time it will warm up is if it idles for long periods. I have a four blade fan on it with a water pump pulley about the same diameter as the dampner. Should I switch to a 3 blade fan or a smaller pulley?

Durham Missouri

I can't see a problem here. Sounds like it's running fine, leave it alone.

If the thermostat is rated at180 and is functioning properly, then the engine is a minimum of 180 degrees.  The factory gauge sender location will indicate a temperature that is about 15 degrees lower than the actual temperature.  The reason is because coolant has to travel over 3 more combustion chambers from the location of the sender.  Where are you getting the 160-170 reading?



Lawrenceville, GA

Ok time to chime in here, First I would check the poundage of your radiator cap! Yes it does make a difference if you don't believe me check it out on line because if you read it on the internet it has to be true! Just a little humor thrown in.  It's a simple and inexpensive test or fix I just did it the other day with a friend with a scruby that was running way too hot as he thought using a 165 thermostat but then he told me he just installed a new aluminum radiator and used the cap that cap with it. No poundage indicted on it, I told him to try a 13 or maybe 15 lb  cap he did and it reduced his temp by 5 degrees. Small difference but in the right direction for him, so I would check the cap first and read up on whether to go up or down in poundage on the cap.
hey just fuel for thought.

It's not a scruby it's a scruby!!!

I have the temp gauge sender in the water pump. The only hole I could find it would fit. I have a infrared temp gun that I'm using to verify temperature. I checked several places water flows and 9 out of 10 times the warmest I find is 170ish. I was worried that if the thermo wasn't opening the engine water wouldn't flow through the block correctly. I'll check into the rad cap. I am using a 3 row aluminum from Champion and never changed the cap. And Lou you may very well have the right idea. Maybe I'm worried about nothing.

Durham Missouri

The water pump is the worst place for a temperature sender.  The coolant is just coming out of the radiator so at best, you will get a reading that is a few degrees higher than the cooled coolant coming out of the radiator.  The coolant still has to pass by 8 cylinders and over 8 combustion chambers.  From that perspective, it is no surprise that you are getting a lower than expected reading.

The best place to check the temperature is right behind the thermostat, on the intake.  If the device you use to measure is known to be accurate and it is only 170 there and and does not get hotter, then your thermostat is defective or perhaps is was mispackaged, or maybe it is a 160 and poor eyes made it look like 180.  The thermostat is opening.The engine simply will not stay cool if the thermostat does not open.

You should see the temperature increase as you measure along the flow of the coolant.  The pump will be coolest, the middle of the block will be warmer, the stock sender location will be warmer, the thermostat will be hottest.  Do you see that?



Lawrenceville, GA

A word about caps. DO NOT TRUST WHATS WRITTEN ON THE CAP. We run a very high # cap on our dirt track engine; after many failures we bought a tester and four 3 different caps that were over 25# would bleed at less than 10#. We now test every one and scribe what they are. I use a 7 psi cap on a heavy duty 3 core brass/ copper rad in my 56 with a 160 thermostat. It runs 160-170 at the top hose at idle and a little lower when running on the road.
Always check your water movement at idle with the cap off, if you don't have any install a smaller pulley.. Good luck.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Every Y block I have seen has the sending unit in the back of the drivers side head. Threaded hole there. Most of us wish we had a too cool problem!