Cummins 8.3 - Full Air System

I have a pin-hole airleak [that I can reach-in from the starboard engine compartment and place ONE finger-tip over] around the lower half of the head of the Air Compressor.

I am assuming, depending-on "where" in the "stroke", when the compressor stops running [or on shut-down of the vehicle], it allows nearly all the air to escape from the holding tanks ...sometimes "not", as this is an intermittent leak.

This is a very "audible" leak, like air escaping thru a pin-hole in a tire ...feels that way also upon palpation.

Any ideas of the complexity of this repair and, of course, estimated COST???

Appears to be a Head Gasket leak...

Robin: I suggest you confirm this is a "leak" and not a designed feature. My 8.3 has air in the front for my "auxiliary": air hose connection, etc. and somewhere in/on the the air manifold it has exactly the same intermittent "leak" that you're describing - and it is a long way from the compressor. I'm not saying you don't have a problem; just confirm it. Perhaps Bill N.Y. has an answer. Please post your result.

The air compressor should have a check valve installed at your air dryer and or tank - this keeps the air from back feeding and leaking down.

The air leak could be the air conditioner vacuum unit - it could also be your air gov.

Lets say it's the head of the compressor - in my book, changing out the head gasket is rated a 3 on complexity scale for a novice - thermostat would be a 2 - you should have no problem if you can get to it.

Location, location, location.

The compressor is kinda buried-in-there and possibly out of the scope of my ability or tool requirement.

It is definitly coming-from the seam [gasket] between te head and body of the compressor.

A little larger than a pin-hole [as originally stated] and is audible from anywhere outside-of the vehicle. You can put your finger over-it and completley occlude the breach between the head and body of the compressor.

Thank-you for the input, as I investigate further into this potential repair.

I am assumimng that when the compressor stops with the piston in the up-stroke position, it blocks the "escape-route" and the system can hold air for days ...if the compressor stops with the piston in the down-stroke position, the air is able to by-pass everything and make-it to the escape-route.

Does this sound-like a reasonable expalination to the intermittent nature of this "leak" -or- am I totally off-my-nut in evaluating this???

[B]Does this sound-like a reasonable expalination to the intermittent nature of this "leak"....[B]
Not only does it sound reasonable, I agree with your diagnosis. Good Luck.

quote:

Originally posted by Medic37:
Does this sound-like a reasonable expalination to the intermittent nature of this "leak" -or- am I totally off-my-nut in evaluating this???

Sounds plausible. Most all (99.9%) systems have a check valve between primary and secondary systems.

If you have an air dryer there is also a check valve between the dryer and the compressor.

Pay a professional to change out the head gasket - because you need to drain the coolant have them also change out the T-Stat and get it flushed too.

The air compressor is liquid-cooled? That's interesting!

Liquid-cooled and probably connected to the engine's oil supply for lubrication, no?

Mike

quote:

Originally posted by Rusty:
The air compressor is liquid-cooled? That's interesting!

Most, not all, are liquid cooled in the head & air cooled around the piston area and fed with an oil supply line.

I do not know if his 8.3 is cooled like that.

Quote from the bendix site:
The Air Compressor is the source of energy for the air brake system. It is driven by the vehicle engine, either by belt or drive gear, and on most vehicles, utilizes the vehicle lubrication and cooling system; however, self-lubricated and air-cooled compressors are available in some models.

I didn't catch the 8.3 reference. I also have a 8.3 and it has a Holset SS296-BE air compressor. It is air-cooled. I can't see any oil connection to the engine.

Mike

I had to replace my air compressor on my 8.3 two summers ago. It was a blow-by issue that was pushing oil into the air system. I had a Cummins shop put in a new one. The cost was $815.00. It is mounted on the passenger side of the engine just above the oil pan flange.

The system works fine now.

Bill G

OUCH!!!

...how did I already assume that it could cost up-to or close-to a GRAND in the worst-case-scenario???

As I inspect this further today in bright sunlight, it appears as-if the gasket has a small crack-in-it and this is the space where the intermittent air-leak occurs.

However... Being-that the system does hold air under normal opreating conditions and ALL air actuated components are working just fine, I will need to down-grade this repair for the time-being, as there are higher priority items on the spring "to-do" list and it will definitely be time to begin hitting the road, here, in the very near future.

I really do appreciate all of the comments and informational posts regarding this matter!

Thank-You!!!

What part number do you need?

Would something like this Midland/Holset do the trick?

Or this one?

Or is yours a Bendix Tu-Flo 550 unit?

Or a Bendix Tu-flo 500?

Oh, and while I was wandering around Ebay I saw an 8.3 inframe rebuild kit with pistons, skirts, rings, bearings, etc for around $1500 or best offer. Maybe someone feels like a spring rebuild or something, although I have no idea if that's a good deal or not. Any excuse to browse Ebay!