Radiator Pressure

[buppy69]

What would cause pressure in the radiator to build up and blow into the overflow bottle and even out of it? I've replaced the cap with a 16lb one. The temperature of the water never gets so hot that you can't put your hand in the bottle.

Eugene

 

[kc5dlo]

Blown head gasket?

 

[normde2001]

Start engine cold with radiator cap off and check inside radiator for bubbles, a sign of a glown head gasket, or crack somewhere, allowing combustion pressure into cooling system.

 

[buppy69]

Thanks, I will check for head gasket but this thing runs like a charm. Wouldn't it run rough if it was leaking compression?

Eugene

 

[buppy69]

I just checked. No bubbles. The coolant doesn't appear to be circulating though. (This has a water pump).

Eugene

 

[normde2001]

'Wouldn't it run rough if it was leaking compression?"

Maybe, at this point all you know is that something is building more pressure than the cap can hold. Could be the cap is not seating/sealing properly. Sometimes the only way to detect a blown head gasket is wetness seeping from under the head, or just loss of coolant.

 

[buppy69]

I just let the tractor run until the guage got up to the same temperature where it was building up today, and with the cap off it didn't overflow.

Eugene

 

[LMTC]

What model Yanmar is this? 16# seems high.

 

[1danny]

If you can't see the water moving I would take a look at the water pump. Take the top hose loose from the radiator and see if the water pump is working. The impellar could be worn out or loose. You should have a 13# cap.

Danny

 

[buppy69]

Will do. But if the water pump wasn't working, would't it run hot?

Eugene