QSB 6.7 Aftercooler Service-RTV?

[Joe F]

We asked a Cummins tech to service the aftercoolers on QSB 6.7s and reinstall with Alco Metalube per the guidance on this site. The tech recommends Cummins PN3164067 (Loctite 5699 Grey RTV silicone sealant) to seal between the brass endcaps and aluminum housing ( to better fill any pitting), with the Metalube on the bolts.

Is this an appropriate use for the RTV or should we insist on the Metalube? Coolers haven’t been pulled yet so condition is unknown, just trying to be prepared.
Thanks,
Joe

Topic

[Joe F]

Got it, thanks all.
Joe

[Tony Athens]

Joe,

Simple answer– Get a new Tech..

Tony

[Stephen Oliver]

From my understanding and I’m sure someone else will pipe up.. there is no sealing between the core end plates and the aluminium housing, the sealing comes from the oring between the housing, core and housing ends. The recommended use of metalube is to a) stop a reaction between the core and the housing and to ensure its well lubed so when you bench service it again in 2 years the core slides right out.

The RTV is just going to gum everything up and make life hard on the next service. Stick to what Tony recommends and only that. Years of working on them makes him right. Cummins really don’t know anything about the service side.

If you do have pitting on the housing face you can take the housing down with wet and dry paper on a very flat surface or get it machined. If too much needs taking off you can match the core by machining that also ( I believe), I’d hope it wasn’t that bad tho. Pitting is only an issue onto the sealing faces and not on the face between the housing and core.

Number 1 important thing is after rebuild you must pressure test it. I did mine at 40psi water side and 30 psi air side (couldn’t get the larger fittings to hold any higher) and left for 24 hours each test. No drop means no leak. No leak means no corrosion and no new engine required down the track…

Steve

[Corey Schmidt]

We use 100% Alco Metalube when servicing aftercoolers… it just works. not sure about anything else… although I will say that ANY grease is better than NO grease.

[Author]

Replies