51 Commander Overheating question

[TWChamp]

I see you have a 12 volt battery. I wonder if your gauge is getting the right voltage for a correct reading?

[lelshaddai]

All the gauges have accurate voltage reducers. The gauge seems to be working fine. I had it hooked up to a 6v battery to see if it worked.

[TXCR13]

Freeway speeds generate more airflow through the radiator than the fan does at idle. Overheating at freeway speeds (but not at idle) normally indicates insufficient water flow as the prime issue.

You mentioned you had the radiator "flushed". Did that include tank removals, boil out and rodding out of the core, or just chemical flush with the radiator still assembled? A badly clogged radiator may not get clean from a simple flush.

Also possible your lower radiator hose may be suctioning flat at the somewhat higher freeway rpms, and restricting water flow. A large hose spring inserted in the hose will prevent that. Make sure the spring extends the full free length of the hose.

Common misconception, but changing to a 160F thermostat will not reduce the upper operating temperature of an engine that has a 180F or 190F rated thermostat. If it were that easy, people would be buying $20 100F thermostats instead of $500 radiators. Oversimplified, a thermostat affects the lower range of the engine operating temperature, not the upper. The 160 will open "sooner" (at their lower temperature rating) than the 180F or 190F. But when fully open, it has done its job of warming the engine to its lower operating temperature, but can not flow any more water/ run any cooler than the other stats. Yes, yes, I know that a fully open thermostat is not supposed to restrict water flow but sometimes removing the thermostat will let the engine run cooler, but lots of people will disagree with that. Living in Arizona, you may want to try it, or give a high flow thermostat a try. Stewart Warner makes a good one. But shop around, there are some shoddy "high flow" units on the market.

Adding coolant will not make it run any cooler. Straight water cools better than a 50/50 mix, but most folks need the mix for cold weather protection. And, a mix increases the boiling temperature, which can be important.

Check against the spec and make sure initial your timing is not retarded, and that your advance mechanisms are functioning correctly.
As someone else posted, check to verify you are not running lean.
Good luck with it.

[lelshaddai]

The radiator was flushed and not rodded. It will be rodded out in two weeks. The lower hose has a full length spring in it. The forum guys suggested I use a 160 thermostat since that is what they had in them originally. It overheats at freeway speeds and idle but does better at about 35mph. Looking into water flow problem.

[Rapps]

Hello You should consider your radiator is blocked If you touch the radiator ( If your hand fits down the front ) when it's hot you will feel it is cooler in some areas and hotter in others
Sometimes adding 1 half gallon of white vinegar to your system tat may help move some build up
I did this and it helped for a while but since replacing radiator the problem is resolved
Good luck Lindsay

[doofus]

To remove the freeze plugs drive a long chisel or screwdriver through the center and pry. some will tear,then carefully tap on the outer edge trying not to gouge the block. clean the seating area with a small cup type wire brush. you will need 6 disk type 1 1/2 plugs, i like the brass Dorman replacements. there are bolt in copper plugs also. set the new plug in place,holding a small hammer against the center and wack the small hammer with a shop hammer till the plug flattens in the center. a smear of sealer around the edge will prevent seeps. this is the filthiest job you will ever tackle!!! Be Prepared!!! Luck Doofus

[TXCR13]

The radiator was flushed and not rodded. It will be rodded out in two weeks. The lower hose has a full length spring in it. The forum guys suggested I use a 160 thermostat since that is what they had in them originally. It overheats at freeway speeds and idle but does better at about 35mph. Looking into water flow problem.

I hope the rod out helps, good chance it will.
You may want to talk with the radiator shop about what they intend to paint the radiator with. I have seen some so heavily coated with a soft paint that I think it can decrease cooling efficiency.
Missed the earlier post about you already having the spring in the lower hose. On a related note, make sure your hoses are good condition and resilient, not soft and gummy, which might allow an internal swelling.
Sounds like the 160 thermostat is the right on for the car.
Good luck and let us know how things work out.

[lelshaddai]

So, after reading all the posts I had the radiator rodded out. Looks like the water flow guys win on this one. The shop sent me a video and he said about 20% of the tubes were flowing. I have it back now and ran it at high idle (1000 rpm) for 30 minutes. I also have a coolant filter to see what the engine may belch up. The candy thermometer reached 194. The gauge read just above halfway on the little box for running temps. That is a big improvement. I have not driven it yet out on the surface roads or freeway yet. Granted in was only 75degrees today. But is was in a still air garage. Thanks,
Jim

[jclary]

... I also have a coolant filter to see what the engine may belch up...
Jim

I have often wondered about doing something like that, but never researched it or taken any action to do such. For years, I sold, installed, and serviced all sorts of filters from paints, water, and even high-pressure systems, but never for any kind of engine coolant.

How 'bout posting a picture and give details of your coolant filter and how/where it is installed.

[lelshaddai]

You can buy an inline coolant filter. It looks like a fuel filter. You just cut and place in top hose. The Radiator shop cut out a piece of window screen and it was placed around the top port, then the hose slide on. He swears by it to get the big stuff that will plug up the tubes.