Radiator Cap Conversion Article

[rv_safetyman]

I am trying to get a quick article together for Chad on the subject of converting from an over-center cap/pressure relief valve system to a standard car type system.  

The Eagle model 10 on up uses the system shown in the photo.  Do other types of buses use this system?

Also, if your bus uses the standard automotive cap, what pressure is recommended?  Eagle seems to recommend 7 pounds (Series 60 manual says 9 pounds).  Anyone gone to a higher pressure?  

Jim

[HighTechRedneck]

The type in the photo is what my RTS uses.

[johns4104s]

The one on the left looks like the 4104 cap.

John

[luvrbus]

Jim, our 1996 Prevost had 2 caps on the surge tank both looked alike but the filler was a 18# and the pressure relief was 14# with a series 60.  
Sorry I can not post a drawing for the system, maybe one the Prevost guys could do it for you or I can mail you one from the parts manual.
The system to me was stupid using 2 different radiator caps at different pressures when the 14# would have worked by itself on the fill because it was a 14# system there was no need or reason for the 2 caps. I changed the over center to a 7 # cap and recovery jug on my Eagle years ago
good luck

[rv_safetyman]

Thanks for the replies guys.

I should have identified the parts.  The part on the left is obviously the over-center locking "cap"/filler.  The part on the right is the pressure relief valve according to the Eagle manual. 

Looks like GMC used the same system.

I really don't like the system.

Clifford, no need to send the pages.  It is not that important to the article.  Just want to know if I was only writing to the Eagle owners.  Glad that the audience is broader.

Jim

[gumpy]

MCI (5, 7, 8, 9) use the setup shown in the photo.

[FloridaCliff]

Jim,

The GMC 4905 was using the over-center until the end of production.

Cliff

[John316]

Jim,

Our 1995 DL3 uses that over the center cover.

God bless,

John

[belfert]

Dina uses the over center type locking cover on the filler for the surge tank, but the surge tank also has a regular modern style radiator cap on the top of the surge tank.  I was going to have a shop replace the water pump once because it appeared to be leaking, but the shop said the radiator cap was bad instead.

[Len Silva]

I don't remember the exact number but the 4104 pressure was very low, like 3-4 lbs.

[mikelutestanski]

Hello:    Mci 7 uses a 4 pound relief  .   Mci 9s use a 7 or 8 pound relief.  THe relief is on the top of the overflow tank and is a bear to get at if you built in stuff over and around the area. The top of that tank sits just under the top rail of the rear section of the bus. 
    Regards   mike
     

[MCI-RICK]

Jim,

My 1990 MCI Classic uses the over-center locking cap/filler.

Rick

[luvrbus]

Pressure has doing to do with the temperature of a radiators all it does is raise the boiling point 3 degrees per pound to keep the coolant inside the cooling system.  
My system on the Eagle has a boiling point of 233 degrees far above the operating temperature for a 2 stroke.
A little info you guys thinking like I did more pressure would make the engine run cooler.    
good luck

[jjrbus]

Very simple conversion

[NJT 5573]

Jim,

Before safety shutdowns, they kept the pressures pretty low on over the road equipment. Its a lot harder to maintain a higher pressure system and keep the coolant in the system vrs. a lower pressure system.

Many buses have several hoses that are difficult to get to for replacement and service, so if you get a leak in a hard to reach area it can keep you down for some time to get a good repair. Several of the hoses on my 20 look to be engine removal time if they need replacement. If you had a real accessable cooling system it would be much easier to keep up. 

Lower pressures don't tax the hoses and hose clamps nearly as much as higher pressure systems. The heat rejection is best with higher pressures, but you have to keep the coolant where it belongs, so you gotta give up something to get something.

I think the life span with rubber hoses is longer with a lower pressure system as well. Many times with the older equipment with no safety devices and the driver sitting 30+ feet in front of the engine, a cooling system failure meant an engine failure.