Cummins QSB - Aftercooler O Rings

[steved]

Recently had both heat exchanger and aftercooler overhauled and serviced by a Cummins authorised dealership. Thought I spend the extra to get the job done properly..

I had previously purchased all the seals and O rings from the same dealership a couple of months before having quoted the engine serial number etc . During the aftercooler rebuild one of the engineers commented that the replacement O ring was thicker than the one removed, citing that Cummins must have made a design change. After the rebuild the unit was pressure tested as per Cummins manual, and refitted to the engine.

Didn't think too much about the thicker O ring until I was looking to buy some further spares from the US and noticed that the aftercoolers on the QSB had 2 different thickness's of O ring fitted, and this particular US provider (SB Marine - excellent website for Cummins owners - www.sbmar.com) provides 4 O rings, 2 thin and 2 fat to ensure that the right ones are fitted.

I have now looked that the aftercooler again and notice that there is a slight gap between the end caps and the main aftercooler unit, presumably due to the thicker O ring. I have queried this with the dealership and await there response.

So what do the engineers amongst you think, am I risking a disaster by still running the engine with potentially incorrect O rings fitted?

Thanks all

 

[ARE]

Do you have QSB 5.9 or 6.7?

 

[steved]

Do you have QSB 5.9 or 6.7?

It is the QSB 5.9

 

[Bouba]

Recently had both heat exchanger and aftercooler overhauled and serviced by a Cummins authorised dealership. Thought I spend the extra to get the job done properly..

I had previously purchased all the seals and O rings from the same dealership a couple of months before having quoted the engine serial number etc . During the aftercooler rebuild one of the engineers commented that the replacement O ring was thicker than the one removed, citing that Cummins must have made a design change. After the rebuild the unit was pressure tested as per Cummins manual, and refitted to the engine.

Didn't think too much about the thicker O ring until I was looking to buy some further spares from the US and noticed that the aftercoolers on the QSB had 2 different thickness's of O ring fitted, and this particular US provider (SB Marine - excellent website for Cummins owners - www.sbmar.com) provides 4 O rings, 2 thin and 2 fat to ensure that the right ones are fitted.

I have now looked that the aftercooler again and notice that there is a slight gap between the end caps and the main aftercooler unit, presumably due to the thicker O ring. I have queried this with the dealership and await there response.

So what do the engineers amongst you think, am I risking a disaster by still running the engine with potentially incorrect O rings fitted?

Thanks all

My gut feeling is if sbmar say to fit the right one then you need to fit the right one, I take sbmar as gospel

 

[burgundyben]

My gut feeling is if sbmar say to fit the right one then you need to fit the right one, I take sbmar as gospel

Correct. Tony Athens wont be wrong.

 

[ARE]

The QSB 5.9 was fitted with two different affercoolers, the early one (4019968) had the thicker O rings. The superseded one (3979771] had the thin O rings fitted. If you let me have your engine serial number, I can check if your engines have the early or late aftercooler fitted.

 

[steved]

The QSB 5.9 was fitted with two different affercoolers, the early one (4019968) had the thicker O rings. The superseded one (3979771] had the thin O rings fitted. If you let me have your engine serial number, I can check if your engines have the early or late aftercooler fitted.

Thanks ARE, appreciated.

The engine serial number is 46789110.

 

[ARE]

Thanks ARE, appreciated.

The engine serial number is 46789110.

You have the early aftercooler fitted and as such you should have the thick O rings fitted.

 

[steved]

You have the early aftercooler fitted and as such you should have the thick O rings fitted.

Excellent, thanks ARE, so that would suggest that prior to my ownership incorrect O rings had been fitted at some point, I'm glad I checked it out, the Cummins dealership confirmed the same, and believe you may have had the some discussion with them.
Just goes to show that paying the extra in labour costs for the services of authorised dealers for some types of work does pay off in the long run.

 

[Tex]

What is the approx normal service cost for these engines (5.9)?

 

[Assassin]

Its common policy to use thicker O rings to replace problematic sealing rings as the thicker ring often needs more pressure to flatten then out and once flattened out they have more footprint which means they seal more effectively, especially in dissimilar metals with unequal expansion/contraction rates.

 

[Fishing Fool]

On Cummins marine 5.9 engines with saltwater cooler aftercoolers, the size O-ring one uses is 100% based to the bronze aftercooler cap design------------Nothing else..
The "Fat" o-ring caps we used for a few years on the last of the 5.9 mechanical engine production a and the 1st few years on the 1st QSB.5.9 production..
Lots of issues with these caps/o-rings and Cummins went back to the early caps that used the thinner o-rings...

The caps are interchangeable, but not the o-rings -- The "O-RING" cross section diameter (approx 3mm or 5mm) follows the cap design only.

Typical "o-ring squash' is in the .030-.040" range before the cap bottoms on the housing.

B Series Aftercooler O-Ring Identification

Hope this helps

 

[Portofino]

The lets call it evolution of parts happens a lot .Tiny changes here + there .
Thats why when using a franchised / authorised by the manufacturer supplier they always ask for the serial numbers .
Once on there system you are ok , but the wiser parts guys always double check before you commit to purchase .

Exactly the same with auto parts but its the vehicle I’d number on the screen or chassis stamp if older .
eg the same car over its life might have has 3 alternator suppliers , a Bosch , a Denso or a Marelli .Same size say 60 ah but different mounting brackets not unfortunately interchangeable.
They will know which chassis numbers apply to which parts .

Nothing particularly new here .It’s a good sign they collect the numbers before taking your money and dispatching parts imho .

Which is what’s happened.