Surge tank , system pressure vavle

[bobrl]

Good evening form. My name is Bob in Illinois. I have a 1958 4104 ,6-71. I had a issues today that i cant figure out. I just installed all new coolant hoses and drove the bus yesterday for say 10 miles , all was good till the air compressor over charged the system and i heard a weird noise , found that the safety valve released because of too high pressure !! Never heard that before!! Cant find this "safety valve any where! Manual says it is installed in the rear air tank!! I cant find it!! Any way back to the surge tank and the cooling system pressure valve !  Today i idle the engine for 10 minutes , watched the temp , never moved the temp gauge, i was checking the air compressor building up air , and it stopped at 105 ! Great. Shut down engine! Walked to back end and on left side on the floor was say two gallon of coolant on the floor!!!!😩 so my question is what happened??? I think the cooling system pressure valve released, why i dont know and dumped the coolant out. So i have been checking and the pressure valve is now stuck open!!!! I cant when !!! Any thoughts ? Thanks. Sorry i went on so!!

[chessie4905]

Over filled surge tank. Has air in system and hot air/ coolant  pushed out. Now it is lower than what was pushed out. Very common happening. If you didn't, you should shut off valves before removing coolant. Otherwise, a lot of air gets trapped. There is a bleeder up by heater core to bleed out iny air in that circuit.

[chessie4905]

As an aside, there is a member here SyberD that is collecting all the serial numbers of existing or scrapped 4104's. He would like yours if willing. Since there were over 4 thousand of them, it is quite a challenge for him to collect all that are left. He has been doing this for several years and has an extensive list so far. Welcome to the board btw.

[bobrl]

Thanks for the response!! So shouldn't the cooling system pressure valve reset to closed position?? In the manual it says it takes 3.5 to4.5  lbs to open ,but shouldn't close back , for normal operation? As it sits now its open!!  Wont that be a problem ?? Thanks.

[chessie4905]

Yes, it should. Rusted or broken spring, debris blocking it. It doesn't  have excess pressure right away from cracked head or blown head gasket does it? Maybe pressure has been bad all the time? Just overfilling coolant and air pocket caused this?

[richard5933]

Does your bus have a circulation pump with a switch like the 4106?

Very helpful getting the coolant to the front of the bus.

If you drained the front though, you'll need to open the bleeder as you fill.

[bobrl]

Morning.  I would not know if it has a cracked head or blown head gasket! Is there a way to remove and repair the valve ?  I did not drain the front heater portion ! In the manual it says to open the heater valves at engine bulkhead when starting engine if you have factory GM air!!  But do you have to open the valves if you dont have AC?  Or what?  Sounds confusing 😩

[chessie4905]

You usually only open them if you want heat at front heater core under dash. Some shut them off in warmer weather. Some like to leave them open to use to lower engine temp climbing mountain in really hot weather or because cooling system isnt up to snuff. However it will almost roast you out in the process, but better than cooking engine.

[bobrl]

So it is not nesscary to open them for proper  circulation !  I am at a loss as what to do now ?  Dont think i can run with the valve stuck open !! I havent driven the bus in a while. But it never dumped coolant like that before!  Been having fuel issues , why i havent drove it

[richard5933]

Morning.  I would not know if it has a cracked head or blown head gasket! Is there a way to remove and repair the valve ?  I did not drain the front heater portion ! In the manual it says to open the heater valves at engine bulkhead when starting engine if you have factory GM air!!  But do you have to open the valves if you dont have AC?  Or what?  Sounds confusing 😩

If the 4104 operates similar to the 4106 and other GM models, the OTR a/c uses the heater core to moderate the temperature of the air flow. That's why the valves stay open when using factory a/c.

Before getting worried about a blown head or head gasket, you should make certain that the system is filled properly, with no air pockets. Then run till its at full operating temp for a while. When we opened our system last year, it took a while to get the last few gallons of coolant into the system without it puking back up.

If I understand the way the pressure valve works, it's above the normal coolant level and only comes into play when the level rises and/or the pressure is above the set point.

If the pressure valve fails, might be easier to just replace it if Luke has a new one.

[bobrl]

Thank you for your help!! I am calling Luke in the morning. Cause i think the valve is stuck open. Seems like i fix one problem and just as fast another one rares its evil head. Lol 😁 thanks very much!

[chessie4905]

Be careful removing it. That many years, you can damage where it is attached to the tank when you try to loosen it. Start not and give it frequent shots of PB Blaster penetrant or other penetrating oil.

[bobrl]

The manual give very little info on that valve. Gives great info on most every thing on the bus. But not that!!!! I guess i will have to take surge tank out of bus to get to the valve!!! Whats your history on these Beauties??? This is my first and i have a Love Hate relationship with her!!!!! 😁

[chessie4905]

Yeah, I checked my 4104 manual. Quite a bit different than my 4905. If you have trouble disconnecting hoses, maybe it would be easier disconnecting from engine and remove whole assembly and they remove lines on the bench. Spray all the fittings and mounting bolts. Tank should be brass, so is solderable if you create a leak.😱

[bobrl]

The surge tank is mounted on the bus above the radiator. Will be tough removing!! If it can be fixed !!!