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Friday, July 24th. Getting ready to leave on a trip up to Gosshen, IN. Doing the pre-flight inspection on the Volvo (it has been parked since April).


Build up air pressure and open the valves to drain the air tanks. Out comes a smelly whitish emulsion of oil and water. OK, this is not normal or good. <_<


Get in the truck and begin to build air pressure again. The gauge hits 80 psi and then begins falling like a rock. Look for airline leaks and can find none.


Crawl under truck and notice a tar-like goo around the purge valve on the dryer body. This ain't good either. :(


Take off the dryer body and canister. Remove the canister. Inside both is a thick covering of black tar blocking valves and ports. Figure the stuck valves must be the problem so I decide to replace the whole assembly and drive to the Volvo shop and get a new assembly. New valve body and canister about $260. Mechanic says it looks like my compressor is pumping oil - probably worn out. What I am looking at and calling tar is coked oil/water emulsion - same stuff asphalt is made from. Not happy with this analysis. :huh:


Back home put on the new dryer but still have no air pressure. Disconnect line from compressor that screws into the dryer body with a 1/2" NPT thread and put a gauge on the end of the airline. Pumps up to 35 psi and stops but has no volume.


Start checking around compressor. Air is pumping out the intake like crazy - it should be sucking in. Oh crap, now the compressor has blown a seal or valve. Best to replace since it since it is also pumping oil.


Have to remove the compressor. Drain coolant into two 5 gal buckets. Don’t have a 37mm wrench to take off airline nut. Finally get a pipe wrench on the nut and get it loose. Need to pull gear and fittings off of old compressor to turn it in as a core or pay a $450 core charge. Getting the gear off the compressor end shaft breaks two pullers before it pops loose.


Needed compressor is not in stock. Shop can't order until Monday (today). I could put on a 2 cylinder (in stock) rather than another single cylinder but would loose core ($450) and add another $200 to cost. Don't have a semi-trailer with air brakes so figure no advantage going to a bigger compressor for $650 more. As it is the new compressor is $1,285 with core. :o


The new compressor is due here tomorrow by noon. I'm adding new L and U coolant hoses, metal airline that goes to the rear of the engine, rubber airline that comes off of the metal one and goes to the dryer body. Also add a new governor to the materials list. Previously bought new dryer valve body and canister. Mechanic at Volvo cautions me to watch brake cans 'cause if oil got to them the rubber diaphragm inside could rot. May have to replace brake cans too as a precaution sometime soon. This has turned into a $2K+ do-it-yourself job - glad I'm not paying $119 per hour shop labor on top of that.


The only really hard part is the handling of the heavy compressor. Other than that and the blank-t-blank 37mm compression nut I did not have a wrench for it is very doable. Just a lot of grunt and grease not to mention what I consider over priced parts. If I can accomplish it with my current physical limitations I guess anybody can if they don't mind getting dirty. As expected, there isn't much mechanically I have not rebuilt or replaced on this truck. I chock it up to yet another learning experience. Look at everything I have learned in the past 5 years that I would have missed if I just went out and laid down $60K+ for a new little girlie truck - not to mention the friends I have met on this thread.


The luck in the un-luck is the compressor went south before we left on our trip. - not out on the highway. That would have been a real mess. :)


I just hope re-assembly goes together with no issues.

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I know it's a little late but, my thought is you do not have a "worn out" compressor, but your compressor broke the intake reed valve. A very easy R&R job. I know a lot (too much) about compressors. My company does them for aircraft weapons ejection and I'm designing a hybrid pneumatic driveline for a class 8 truck.

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Stekay - LOL - just a follow up on the boost sensor post - now we know that your into compressors (fancy ones) and air stuff. (not meant as a bad thing) Just a feeling each other out and getting to know one another. Welcome to the group by the way.

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I know it's a little late but, my thought is you do not have a "worn out" compressor, but your compressor broke the intake reed valve. A very easy R&R job. I know a lot (too much) about compressors. My company does them for aircraft weapons ejection and I'm designing a hybrid pneumatic driveline for a class 8 truck.

Yea, I know you are right. But, (always a but -_- ) the compressor also needed a new piston, rings and sleeve (800K miles). None of those parts were quickly available and waiting for them would have caused us to cancel our upcoming trip. The compressor I picked up today was all new - not a reman using the castings from the core I turned in. Someone made a nice profit off of a rather simple single cylinder compressor.


The design of a pneumatic drive-line would be interesting. I understand how easy it is to design a hydraulic fluid drive-line but how do you get the pressure or volume needed for a pneumatic one? In my humble and limited thinking I imagine thousands of CFM and/or pounds of pressure being needed. Can you share more?

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As you may know, hybrids need to stop and start to harvest energy. They are not so good "over the road".






That's me doing a presentation for most of the HDT manufacturers in the bottom picture. Exelis was bought by Harris a couple of weeks ago. They are even more gung-ho on the project. Short story is we fill a 1000 cu-in bottle of air to 6000 psi in under 10 seconds of braking, then use that energy to accelerate up to 0 - 30 mph. That's where most of the energy used is.


Apologies to RandyA for the topic drift -Steve

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In 2007 we paid $690 for a Volvo compressor for our 2000 Detroit Series 60, plus labor

Detroit Series 60 would use a Bendix Air Compressor. stock one is the TF-550 and the bigger one is the TF-750.


if your not in a jam and can wait a few days , the bendix ones can be had for less than $400ish now. (the stock size one TF-550)

i put my 750 on my Detroit for about $600ish before shipping. took my 550 off and threw it in my spare parts box (nothing wrong with it)

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The new air compressor is on and I found a wrench for the "problem" nut (arrow).




The hardest part of the entire job turned out to be on the opposite side of the engine. There is a metal pipe that comes out of the compressor, passes over the fan and turns back toward the rear of the engine. At the rear of the engine it connects to a rubber air line that connects to the under chassis dryer valve body. I purchased a new rubber air line and wanted to replace it due to some serious rust on the compression collar at the dryer end.


The connection from the metal pipe to the rubber air line would not break loose. I tried PB Blaster, heating with a MAPP gas torch, two BIG pipe wrenches and I still could not break the connection. I had one idea left but knew if it failed I would be up poop creek. Using a reciprocating saw I cut off the rubber air line just behind the frozen connection. This allowed me to slip a socket over the nut on the rubber line and use my 1/2" impact wrench. While holding the flare nut on the metal pipe with a pipe wrench I was able to break the nut loose with the impact wrench and get it off. This entire ordeal took at least two hours in 96 degree heat with 80% humidity. It was not fun.


With every thing back together the air system performed perfectly - but I had a small coolant leak around the pipe that attaches to the engine block over the top of the compressor and drops to the heater lines. This required draining the coolant (again), pulling off the pipe and replacing the rubber washer/gasket with a new one. Refilled coolant and ran engine for 40 minutes with no air or coolant leaks.



Serious rust on the compression collar at the dryer end



What it took to get the old air line connector (arrow) off of the metal pipe.



This pointed edge caught my pants every time I slipped in to work on the compressor. I think I will round it off - it doesn't look like rounding will be obvious with the hood closed.



At least I was out of the sun and rain.


Nice to learn that other engines and folks were able to purchase/repair their compressors for less money than I spent. But it is like this - I have what I have, my truck is what it is and I did what I had to do to get mobile again. I could have purchased a used twin cylinder compressor at a local HDT salvage yard for $350 exchange and a 30 day warranty. But, not knowing the mileage on the used compressor nor wanting to have a possible issue out on the road or ruining another dryer valve body I opted for the new one. A reliable air system is essential and I now feel really good about the longer term life of the components. If this one makes it another 800,000 miles I won't complain. That is less than 2 cents a mile :D .

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