Radiator cap???
 

As some know I have just purshased a 2005 f350 PSD.. Then took it to dealer for service.. Everything was OK according to dealer cleaned and flushed coolant, tranny fluid, fuel filter and oil change(see my other post)..

Well the dealer overfilled it a bit so on my 200+ mile trip.. I stopped at a rest stop and noticed that the bottle had puked very little(funny though the fluid was no where near the cap... so wiped everything down and set off again...Upon my arival at my destination I popped the hood and heard a hissing noise coming from the Degas bottle cap(the collant wasn't overheating and was well below the cap)little experiment parked the truck on a decline and shook the bottle a little and coolant puked out a little.. So my question is should the cap vent when its not overheating.. .. Because Im wondering if with the cap venting and the coolant sloshing around in the bottle could cause the loss of coolant??? Should the cap vent when the engine is off and not overheating???( I also noticed that the everso slight downward pressure on the cap stops the venting)

Oh yeah one more thing this morning cold (overnight) When I opend the cap It released pressure..So I believe the pressure isnt leaking down significantly..

Also want to mention there is no smoke what so ever and strarts immediatly..

Thank you

Thoughts and opinions

Ford says that once the degas bottle cap "relieves", then you need to replace it.

If you are worried about leaking head gaskets, then you can get a kit that analyzes for combustion gasses (from the degas bottle). Napa has them.

My local mechanic used what looked like a test strip to check it when I brought it by his place to take a look at it.. Said it was ok..

I am not familiar with Diesel engines... But have noticed some odd things like when you first start the truck it seems to draw from the degas bottle then after it gets hot it flows back into tank and after it cools stays in the same place as hot with maybe a little fluctuation... Then when cold It starts and then level goes down then back up..

I have never noticed this on my Gas cars... Is this normal...

A new upgraded cap is only about 7 bucks. Cheapest thing you could try.

This doesn't work if you add coolant to the system because of puking. The new coolant will dilute any HC found.
In my case, I added a considerable amount of new coolant after the pressure cap vented so I wasn't able to try it out.
I think my egr cooler is bad but will have to remove it to find out.
Right now the truck bellows smoke after each and every stop light.

Good point!

If your egr coolers bad so's the oil cooler.

Well changed cap and all is good ...300 miles and no coolant puking also coolant didn't fluctuate like it did before :-X04.... I thank the diesel gods.... and everyone here for there help...