Radiator cap question

[Mule Skinner]

I have had an issue loosing radiator water. I finally looked at the overflow-fill container cap. This is a radiator cap. It had an 8# cap from the factory. I took it to the parts store and best I could do was a 10# cap. I still notice coolant getting past the cap and dripping out the overflow tube that runs down under the rear. If it is dripping after stopping, it must be dripping even more under a load while moving down the road.
Question is, is an 8# cap correct? Would I be at risk using a 15# cap? Seems more pressure might seal better and solve my coolant loss.
What do you think?
Dose anyone know for sure what is correct? I don’t want to split the radiator wide open.


Thanks,
Dan

[EngineerMike]

Mine came w/a 16# vented cap. I added a coolant overflow tank (plastic jug) w/overflow tube set at the bottom of the jug. I still flow some coolant out when engine is hot, but it gets sucked back in when the engine cools.

[Barrier2]

Hi Dan, I don't believe a higher pressure tank would help seal better. The purpose of the higher pressure cap is to raise the boiling point. With no pressure the fluid would boil at 212 degrees F, add 50% coolant mixture and a 15lb cap the boiling point raises to 265 degrees. A 10 lb cap would give you 239 degrees boiling point. You would want to choose a cap that would raise the boiling point above the operating temperature of the engine as controlled by the cooling system and determined by the thermostat.
Too high a pressure could cause a problem such as blowing a hose, gaskets or the radiator which would be a disaster
When I called Cummins after I lost the cap on my 2001 Dynasty I was told 7 -16 lbs. I choose 10 lbs to avoid any pressure problems.
Robert.

[Dale777]

Mule Skinner,

My 2006 Alpine Coach came from the factory with a 16# radiator cap. Perhaps, someone else knows what the spec is for the 2004 Alpine Coach.

[Rich and Cork]

Mine also came with the 16# cap. When I replaced mine, I did so with the kind that has a lever. This is to more safely relieve pressure before taking the cap off.

[Old Scout]

Make sure you are checking the coolant level in the reservoir sight-glass when the engine is hot and running. Checking it when cold results in too much coolant being added and will contribute to overflow issues.

[Mule Skinner]

Thanks all,
I think a 15# would have a tighter seal since the spring is stronger by design. I think I will change to a 14# or 15#. I’ll also mount a recovery bucket. Then I will know for sure how much I’m losing. Or how much is moving.
I do check when hot and running. The total fill is near 10 gallons. That’s a lot of expansion.
I wonder why the original was 8#’s?
Oh well, next is the front hub’s. Time for oil change.
Then an engine oil change. I have been going to Camping world. They do this for about $200. 30 qts. Is a lot when spread all over the driveway.

[EngineerMike]

Was the 8 pounder for sure the OEM installed cap? Mighta been replaced somewhere along the years.

If you are heading to the Jackson NorCal rally, you will pass near the drive-thru oil change joint right next door to the Flying J at the Hwy 12 offramp of Interstate 5. They quoted between $95 and $116 for an ISL oil change depending on filter. Just get in line behind the trucks. And you can get your rig washed right next to that for $38.50, also on a drive-thru basis.

[Barrier2]

Hi Dan, You might want to check out this thread.
Freightliner service at Camping World?
Robert

[Mule Skinner]

Quote:

Originally Posted by Barrier2 Hi Dan, You might want to check out this thread. Freightliner service at Camping World? Robert

Wow, there is a lot of, well, lets say, untrained workers in the field.

I am not defending Camping World.
The one common flaw with every company is they use people.
I guess I have been lucky at the San Martin store.

Mike, I bought the MH new and the #8 lb cap was what I took off.