Engine Overheating

[63 Willy]

A couple of weeks ago my engine (77 Skylark V6, with a refurbished radiator) was running a little warm but not overheating. The fan was not kicking on and the coolant looked old. Since then i have...

-Installed new thermostatic fan switch
-Manual fan switch
-Drained and backflushed the cooling system
-refilled with new fluid

It ran very warm during a 30 mile highway trip yesterday. Today on a short (10 min) around town trip it began to overheat and steam out.

Any ideas what's causing this? Did the backflush damage something? Thanks for your comments!

 

[Cheepjeep85]

id check the radiator hoses, to see if they are weak and collapsing. it is also possible that there is a bubble in the cooling system, leave the cap off and run it until its warm that should let the air out of the system. have you put a thermostat in it recently?

 

[63 Willy]

The hoses are new.

There is an overflow tube that comes out of the fill neck just below the cap. Would that allow it to burp, or will it only work by loosening the cap?

I have not put a new thermostat in it since I've owned the vehicle. 6 months.

 

[Cheepjeep85]

probably not because its should be a pressure cap. is there any white smoke, or water in the oil, oil in the water?

 

[63 Willy]

No White smoke. Oil looks good.

New info though.

When I refilled the fluid after the flush It took 2 galons. I let it run for a bit to come up to temp and then checked the level and it was still full.

I just now was able to add another galon and it could still use more.

Do you think 2 galons was enough? It might not have opened the thermostat when I let it warm up after the fill. Maybe it didn't have enough fluid.

I don't think that i have last over a galon of fluid since the refill.

 

[BusaDave9]

If the engine is running warm and the fan still isn't kicking in it must be the temp switch or the fan.
You say you put in a manual switch. So if you deliver 12 volts to the fan does it turn on?

 

[63 Willy]

The fan runs fine now. It is only after all of that work that the engine really began to overheat.

 

[BusaDave9]

Okay so if your fan is running and it still overheats then it sounds like you aren't getting enough water through the radiator. One possibility is the coolant thermostat. Another possibility is the radiator itself. I know you said you had a refurbished radiator but since we are talking about a swapped in engine maybe the radiator isn't big enough. How many cores does it have? Is it a stock Jeep radiator?

 

[Cheepjeep85]

I should have held more than two gallons. I bet that was your problem.

DROOOID2

 

[IOPort51]

check the water temperature with a thermometer to check the sending unit/gauge??

 

[Cheepjeep85]

^^^yep there's a good suggestion, but you said it was boiling over so it definately is hot.

DROOOID2

 

[63 Willy]

Thank you everyone for your responses. So I just got it running cool again. The problem was that I did not not have enough fluid in the radiator.

The first time that I filled the radiator after the flush I did not let it get hot enough before re-checking the fluid level. Thus, no fluid entered the block.

This time I left the cap off while it came up to temp and could clearly see the system burping and when the thermostat opened. After the thermostat opened I was able to add another half galon of coolant.

Thanks again for the posts.