Hi,
I have 99 Ram 2500 v10. About 6 mos. ago I noticed the resevior going down. ( I had bought truck then-81000mi.) I saw trails from the weep hole and shaft so had the pump replaced. O ring was broken. Thermostat replaced. I still was losing coolant along my trip with trailer. I finally stopped at another repair shop after buying dye and light that showed leaks from the top hose going into the therm. I had the guy take it off and it was coated with calcium. The previous guy didn't clean it! So, he sanded it clean and applied permatex hose goop. I still was losing coolant and the most obvious was that some was coming right out of the resevior cap. But not all the time. Also, I checked tonight with the light and see no leaks anywhere else.
Now- I read that some reseviors are pressurized on various vehicles. Considering that the Ram cap is loose fitting I guess it is NOT. But, anyway, I cut a round piece of gasket material and fitted it in the cap so it fits tighter and not splash out coolant.
Did I do the right thing? Seems sensible to me. ha

 

The reservoir cap or radiator cap? The reservoir needs to breath! Don't cap it off. The resevior shouldn't be filled all the way just to the full line on the side so it shouldn't come out there. If the radiator cap is leaking just replace it.

 

My reservoir system has never worked

 

Why not?

 

It just doesnt lol

 

Mines always full of bugs. I clean it 10 times a year and they keep crawling in. But the reservoir will constant move up or down depending on motor temp. Coolant expands when hot and excess goes into the reservoir. When the engine cools the fluid will flow back to the radiator. I mean if it's not overheating and running fine I wouldn't worry about it. I had a dakota and the reservoir had a huge hole in the bottom . The radiator alway ran 3/4 full. If I filled it up. When the truck was warm it would spit it back out. So I quit wasting my time and the truck ran fine like that for another 100k miles. Still running like that lol

 

Well, I see that OEM replacement caps-yellow- don't have gaskets but I'll leave mine in. If the bottle needs to breath the overflow tube should do that. My oil is clear and my oil fill cap doesn't have the brown anti-freeze on it. My engine does not overheat even pulling my trailer. I will probably have my coolant checked for gasses which would indicate a head gasket leak.
Update 8/9 Well, I found that Oreilly's loans the 'block tester' and I only had to pay for a bottle of liquid. I saw NO color change! Indicating that I have no head gasket leak.
Now, at this point, I see just the fluctuation from add to 'near' full and back.
I cleaned the weep hole of my new water pump(after a few months) and see no leakage there either. It did leak some when I first bought it six mo. ago. I read on the web that it is normal to leak a little for a while then stop.
Update 10/23/15 Well, I saw that while it does go up a little and down; it goes down further after a while. I had a shop do a BG flush. ( I hope. Didn't watch. After seeing it go down again I put in the bottle of BG stop leak. After a 1k mi. it STILL goes down further below the ADD mark!
WTH?