Cool/Heat: 51 Commander Overheating question

[lelshaddai]

My 51 Commander was overheating. It would be fine for 15 miles then peg hot. Thought maybe the thermostat. Took the thermostat out and tested it and it opened up right at 180. Pulled radiator out and flushed it. Replaced water pump with rebuilt one I had on hand. I flushed the engine out. I am running straight water in it right now. After running around the block a few times and letting it idle in the garage for 20 minutes, this is what the gauge shows. it was 75 out today. Is this OK temp for this? Is still seems warm to me. It may get better after I add the antifreeze.

[Jeffry Cassel]

Looks fine. If you are really unsure take its temp with a candy thermometer -but don't scald yourself!. I have an IR thermometer that wasn't expensive and is very accurate.

[Kurt]

That’s where my 51 runs when sitting idle. When you flushed the block, did you pull the plugs and dig all the crud that accumulates in the block out? If not, you may still have heating problems. If you didn’t swap the thermostat out, I would. Sometimes they randomly stick.

[altair]

I think the manual calls for a 160 thermostat try that and see if the temp comes down. When I flushed my block I removed the plugs and removed about a quart of sludge.

[6hk71400]

My 52 Commander in Tucson would always be at the half way mark. That was with a 50/50 water and antifreeze. I don't remember the pressure of the radiator cap but it was to old style flat radiator cap.

What pressure radiator cap are you using? Sometime something small like that can make a difference. Check the condition and replace if bad with the correct pressure cap before changing the thermostat.

Bob Miles

[lelshaddai]

I am running a 4lb cap. When you say pull the plugs are you talking about taking sludge out of the cylinder?

[TWChamp]

No, remove the welch plugs. Also called core plugs and soft plugs. This way you can get out the sludge that settles in the bottom of the cooling system. Once it's cleaned out, then be sure to use 50% antifreeze, so more rust and sludge doesn't form.

[lelshaddai]

OK, that makes more sense. Removing freeze/welch plugs I understand. I have done that before. Just was not thinking that way. Age is creeping up on me.

[lelshaddai]

I have tried several things you guys have suggested now with no avail. new 160 thermostat, changed water pump, 4 lb cap , spring in lower hose, cleaned out as much stuff out of block but did not removed welch/freeze plugs yet. Did not want to pull engine yet. My mix is about 40/60 on antifreeze.

Right now it heats up on the freeway, 65-70 mph, has 3 speed Automatic drive, then when I get on side streets it cools down a bit, then heats back up at stop lights. I think the freeway high rpms may cause some heat. I know it has to be air flow or water flow. The temp at idle gets to 208 and boils out. I am getting vapor lock. I installed a electric fuel pump to turn on when that happens and it helps. What is a good way to test radiator flow? When I run a hose full into it it never fills up to the top. The water runs out as fast as it goes in. I am trying to keep in original if I can. I could replace the radiator with aluminum but really do not want to. There seems to be very few rad shops anymore that clean out radiators. Is that the next step? When the radiator reads 200 temp at top it reads 170 at bottom. Does that not indicate cooling? Timing is right on. Temp gauge has not spiked all the way to H yet, but I think 208 is too hot. It is only 85 in AZ right now.
Thoughts?

[gjamesk]

If you need a good old school radiator shop take it to Hays Radiator, 20th St & Indian School in Phoenix. He cleaned, pressure tested and painted mine, it's good as new.

[lelshaddai]

Thanks , Gary, Spoke to them. I will take in into them in a couple weeks. Interior being done next week.
Jim

[fatboylust]

Sludge: in the end I collected a pint of rust/mud from the two sides.

[lelshaddai]

Is there a way to pull those plugs without pulling the engine?

[64V-K7]

If it's heating up at highway speeds, check your timing, could be late or not advanced enough. Maybe a vacuum leak, leaning out the mixture?
Do you have a bug screen in front of the radiator? Another thing about that sludge is that the temp sender is RIGHT behind that area that gets all the buildup, #7 cylinder.

Your gauge reading does not look too bad, if it were closer or pegged, then I'd get concerned. maybe get a new or used gauge and see what it says. Same with the sender. All these things have a range of wiggle room. No two will read the exact same

[lelshaddai]

When I used my IR temp gun it would read about 160 at the sensor but the candy thermometer would read 200 in the radiator. The gauge has gotten above the normal range and has gotten close to pegging but has not. It has boiled over out the tube several times even with the 4lb cap. I checked for vacuum leaks before. I will do it again. Adjusted timing and dwell several times and I think it is close to dialed in. The heat is causing some vapor lock and hard starts after it runs for awhile. The electric fuel pump has help. The lines are wrapped in rubber right now to help insulate them. I am constantly looking at the temp gauge and just waiting for it to die on me from the vapor lock.