Simple wat to test coolant flow at home?

[WinDancer]

I am still having a little problem with my truck overheating at very low speed.
The radiator, thermostat and dual electric fans are all new and working correctly. There are no fluid leaks.
How do you test coolant flow and the water pump?
TIA,
Dave

[chevy72blu]

Hmm.. good question. I dont know a way to test the system other than if it is cooling adequately or not. What is your ethylene glycol/water mixture? Too much antifreeze can hinder cooling.

If you water pump isnt leaking from the weep hole, it is most likely happy.

It could be that your cooling system just isnt up to par for your motor. What are you running?

[justcuz]

When the truck is cool, take off the radiator cap. Start it up and let it warm up. When the thermostat opens it will over flow slightly then drop to an inch or so below the neck of the radiator. You should be able to see the water flowing from across the radiator into the side tank. It should be moving fairly fast. if it is not have your radiator rodded out.

[slomotion]

It's hard to tell without knowing a little more about your set up, but from what you've described, I'm guessing on the highway you're OK. What percentage of your radiator do the fans cover? It may be that a good portion of your rad isn't working well at low speeds because the only effective air flow is at the fans. Are they shrouded? Are they mounted vertical or horizontal? What is your radiator cap rated at? You might want to have it tested. How hot is "overheating"?

[toddtheodd]

What is your thermostat set at?
Have you done any mods to your engine?
To best answer the questions about your electric fan setup, I suggest taking a picture and posting it.
Have your reverse flushed your radiator? Might be a little something something in there clogging it that a reverse flush could fix. Just take both hoses off and jam the garden hose in the bottom spout with a rag and turn on the water. Should blow clean and clear out of the top spout.
You don't have an under-drive pulley system on there do you?

[70GMCer]

Are your fans turning the wrong way? See if they are pulling air into the rad. or pushing air out from the engine compartment. You want to be pulling air in.

[toddtheodd]

Originally Posted by 70GMCer

Are your fans turning the wrong way? See if they are pulling air into the rad. or pushing air out from the engine compartment. You want to be pulling air in.

Good one... Didn't even think of that one.

Also, are you sure the fans are coming on? Blown fuse or bad wires? (This is just a shot in the dark, because I know I can hear my fans even with my loud a** exhaust)
Todd

[WinDancer]

The engine is a 396.

The entire cooling system is new.

New radiator. You can see coolant circulating after the thermostat opens.

New thermostat. Opens when engine reaches operating temp.

New dual electric fans pulling air through the radiator.

New heater core.

All new hoses.

We have a driveway almost two miles long. The temp starts to climb when I stop to unlock the gate, drive through the gate, relock the gate and get back in the truck. When I get to the house and shut the truck off the engine temp climbs about 9/10ths on the temp gauge to pegged.....

[steelhorse]

Does it sound like it is overheating/boiling over.Could it be that the guage is wrong?One other thing is if you are running a serptentine belt is the water pump turing the right way?Usually overheating only at slow speed is a sign of the fans not pulling enough air.

[airdale94]

If everything is new, you shouldn't have a flow issue with your radiator. Get one of these.

http://www.autoanything.com/coolers/60A3517A0A0.aspx

There opening and closing is alot more controlled. It cured an overheating problem I had one time with a big block Pontiac. I diddn't want to use the heavy duty fan clutch because it was using to much gas.

[clay68c10]

It's worth checking your coolant temp with something more accurate than the factory gage. Mine is starting into the red at 190-195, and that's really not hot for a BBC. I'll be playing with the resistor on the back of the gage to 're-calibrate' it.
With the a/c on and sitting in traffic, I'll see 220-230 no problem, but it's not barfing out coolant or giving me the death-boil when I shut it off. The overheat zone on the 90's TBI trucks is around 260, so I figure it's not a big deal.

[WinDancer]

Thanks for the ideas, guys
It doesn't boil over or spit after turning it off.
It may just be the gauge- that would sure be nice!
How do I get an accurate temp reading?

[68gmsee]

I bought a radiator cap/temp guage from Auto Zone.
http://www.autozone.com/selectedZip,.../selectZip.htm

My truck seems to be running somewhat higher than normal when the outside temp gets into the high 90's, but the ragiator guage shows 180 degree range. I guess I'm okay with that as long as it doesn't boil over.

[steelhorse]

Most new cars run in the 200 to 220 range.My Dodge runs at 200 all the time.I personally dont like to see anything above 220 preforably 210

[cdowns]

Originally Posted by WinDancer

Thanks for the ideas, guys
It doesn't boil over or spit after turning it off.
It may just be the gauge- that would sure be nice!
How do I get an accurate temp reading?

go to a supermarket or home store and buy a meat or better candythermometer wich can easily be checked for accuracy by boiling water and dipping thermometer in(water boils at 212degrees at sealevel)

[chris71]

you may think of tossing in a new water temp sending unit as well (part that screws into the cylinder head or intake) i believe their only like 10 or 15 bucks. also is your radiator cap new and the right one? i have heard that a closed system overflow type cap is different from a non overflow style cap? and its a good psi rating, like 16 psi. if the cap is old and worn, you are reducing the boiling point of the collant. make sure your rad hoses arent collapsing and have the springs in them, i have seen a top rad hose on a streetrod completely flatten out and basicly kink because it didnt have a reinforcement spring inside

[Ackattack]

Do the fans have a shroud and pull air through the radiator, rather than around the radiator?

Pics would be best.

[jorgensensc]

okay,
Similar situation, but different vehicle. In the Bel Air I have Vintage A.C. I had the original radiator recored to handle a 350 w/ a.c. I have a mechanical clutch fan as well as a pusher fan on the front of the radiator with a very mild 350 in the bay. Before i put the electric fan on and without a shroud and no a.c the car would run cool all the time. After putting the shroud on, and the electric fan on front (hooked to a thermal switch that comes on at 175) the car runs up to around 210 all the time. If I run the ac it gets to about 220. I now the gauge works because I hear the fan kick on about midway through the gauge (halfway point on a cold/hot gauge) Could the electric fan really be impeding airflow that much? When I added the fan shroud I had to go from a 18" mechanical fan to a 16" mechanical fan. Is it possible that could also be the culprit. I have A.c. but don't want to run it because of the hi temps. Should I just get an aluminum radiator and be done with the problem? Any thoughts or ideas.

[chris71]

from what i hear when you have a shroud the fan blades should be sticking half way in the shroud and half way out of the shroud, is this what you have, i have seen a few cars that have been modified from this by accident and this was an issue.

[WinDancer]

Temp reading radiator cap will be picked up tomorrow and tested next time I drive my baby
I will post again after.Thanks again for all the input and suggestions.
I did drive the truck to work and back today and the temp gauge never went above the centerline.
Thanks to all,
Dave