- 525
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- Jupiter/FL
I can not run my truck for a week open radiator cap and it's still under a lot of pressure? Is this a normal
Thank you,
Thank you,
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Radiator cap pressure
- Thread starter jcollings
- Start date
Yes. I have seen trucks that have sat on forest service lots for awhile and they still have coolant pressure when the owner checks em at arrival.
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If you have excessive pressure in your cooling system, that is a bad sign. Need to check oil for water? Possible head gasket(s) cracked head or block, liner.
Nothing good.
Nothing good.
- 525
- 347
- 63
- Location
- Jupiter/FL
it doesn't seem excessive it just seems like I wouldn't expect to have pressure. like on other vehicles after overnight not having pressure. wear this after a week still has pressure.
Thank you,
Thank you,
74M35A2
Well-known member
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I think a lot of them do this, have seen it written here before. Mine does it also. I would not think anything of it.
lindsey97
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Check for shutterstat failure.
A failed shuttersat allows air pressure from the on board air system to leak into your cooling system thru the bad shutterstat and force the coolant out of the overflow tank.
You will swear it is a bad head gasket. Had this happen on one of my M923, it puked coolant with the cap on going down the road. Replaced the cap, same symptom. Replaced the shutterstat with a new one and problem resolved. I also noticed the fan staying engaged longer right before the coolant loss began.
I have read that a shutterstat can be rebuilt, but I haven't tried yet. Supposed to be some grease, and a couple O-rings.
A failed shuttersat allows air pressure from the on board air system to leak into your cooling system thru the bad shutterstat and force the coolant out of the overflow tank.
You will swear it is a bad head gasket. Had this happen on one of my M923, it puked coolant with the cap on going down the road. Replaced the cap, same symptom. Replaced the shutterstat with a new one and problem resolved. I also noticed the fan staying engaged longer right before the coolant loss began.
I have read that a shutterstat can be rebuilt, but I haven't tried yet. Supposed to be some grease, and a couple O-rings.
- 525
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- 63
- Location
- Jupiter/FL
location of the shutterstat?
Thank you,
Thank you,
Thermostat housing. Has a air line from the treadle valve and a line going to the fan clutch.
best way to test if its a stutterstat puking air across is air bubbled in the overflow tank while its running with the fan clutch on or off. Kinda hard to do the on unless you get it quite hot. Or another way to test is after driving it hard getting the fan clutch to come on several times. Park it. and dump the air on all your tank drains leaving the truck empty of air. wait 24 to 48 hours and pop the radiator cap if it still has pressure then you know its not a stutterstat.
best way to test if its a stutterstat puking air across is air bubbled in the overflow tank while its running with the fan clutch on or off. Kinda hard to do the on unless you get it quite hot. Or another way to test is after driving it hard getting the fan clutch to come on several times. Park it. and dump the air on all your tank drains leaving the truck empty of air. wait 24 to 48 hours and pop the radiator cap if it still has pressure then you know its not a stutterstat.
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lindsey97
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- 525
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