The Stovebolt Site Forums The Shop Area The HiPo Shop Coolant temperature?

I have got my new crate motor installed and have just fired it up. Man does it sound sweet!

I have a question related to the cooling system -

I have filled the radiator with 4 gallons of 50/50 fluid, put on a 14lb cap, installed hoses with the coils built in. As per the instructions from the builder - no thermostat yet.

As it was sitting still and idleling I was watching the gauges, and I never saw the water temp gauge show an increase. The lowest value shown on the new gauge is 100 degrees.

I gave it just a few minutes before I shut it off because I don't want to run it more unless I am sure it is cooling correctly.

How long should I let it run in order to show a change on the gauge? Or do you suppose something else is happening?

I also have not seen many bubbles come to the top of the radiator and the hoses felt warm.


Maybe I am just showing my inexperience, but does anything think something may be preventing the coolant flow?

Or do I just need to be more patient before I see a temp. increase?

Thanks!

Are you using a direct-reading gauge, or an electric one? The direct gauge will have a very thin tube surrounded by a spring-looking shield that bolts into an adapter on the side of one of the cylinder heads. The electric gauge will have a wire going to the sending unit somewhere on the engine, either the cylinder head location, or one near the thermostat housing. You can test the direct gauge by putting the sender bulb into a pan of boiling water. It should read 200 degrees or a bit more. If you ground the wire from the electric gauge to the sending unit, the gauge should go to a full hot indication.
Jerry

If you dont have a thermostat, the coolant never gets a chance to slow down and pickup heat. PUT A THERMOSTAT IN THE ENGINE. Yes, thats yelling.

Your builder should be ashamed of himself. restrictor orifice or a thermostat with bleed holes would be the only bypass devise to use. Not go without a thermostat.

assuming you have a functional gauge .... what Scott said, if you don't have a thermostat the system can't work as designed - the rad is sized to drop the temp by 50* or more each pass, if you don't "force" the temp up with a proper rated thermostat, it'll never get there

get a good thermometer and check the water temp coming into the top of the rad to verify the gauge - after you get a thermostat

Bill

Hotrod and Scott -

Thank you both for the valuable information.

I will get a thermostat in tomorrow before I start it,and I will test the gauge to see if it is woking. The gauge is electric so I will ground it out before I try the other option and have fluid to clean up.

The builder recommended that you run it for a short time to be sure the air is out of the system. I have never put a new radiator to a new block before so I was going off of his installation instructions. Beging a novice, I learn something new every day.

I will let you know what happens tomorrow afternoon.

Thanks again! I REALLY appreciate your advice.

The rad will purge itself of air eve wth a thermostat installed. Most problems with trapped air in cooling systems involves conditions where the highest point in the water jackets in the engine is higher than the highest point in the radiator. Most vehicles with that design have a bleeder screw to purge them. In the case of these old trucks, that shouldn't be a problem, some do put a 1/8" purge hole in the thermostat flange to assist in puerging. I would be very leary of accepting advise from the engine builder without double checking first.

Before you open up the system to install the thermostat, cover about 2/3 of the surface area of the radiator with a piece of cardboard. When you run the engine, the temperature should rise because of the restricted airflow. Don't run it for long that way, but you should see a pretty definite temperature rise. Another trick we used to use to prevent an air lock was to leave the upper radiator hose disconnected during the radiator fill-up to be able to see when the block, heads, intake manifold, etc were full.
Jerry

That's how I did mine. Didn't do the purge hole trick with the thermostate, but could clearly hear the air hissing out as I filled it.

Scott and Bill came up with the (only?) answer

I asked my 86 year old step-dad who owned and operated an automotive machine shop for 40 years (closed it 10 years ago because of all the electical/computer crap as he put it on cars). He told me it was not uncommon to not put a thermastat in the older engines but the newer engines you have to, so the engine will run at the right temp. He also said if the engine was not running at the correct temp +/- a few degrees that you will start to see more problems down the road