Problem Building Air Pressure when cold

After talking to a driver who was broke down cause his truck would not build air, & talking to my shop guy, I went to the truck parts store & bought an unloader kit for my compressor for $12.00 it's in my side pocket ready to use if needed. mine was replaced years ago, when I had similar problems,but at that time I did not interest myself in what the cause was, just happy to be fixed. that was over 9 years ago. unloader is my bet. they also can leak, too. a lot. but the truck does have to be running to check for leaks, I found. anyway, a spare unloader kit is good to have regardless.

 

Since it is a Volvo, is the govenor or kick-in controlled by electronics at all??? I have no clue about a Volvo truck, but if it is then I'd check that as well. It is almost like you are not getting a solinoid to click to something since you say you cannot hear ANY air leaking but it will work AFTER to restart the truck....weird

 

I've been calling around, from what I understand, the only way to replace the unloader is to replace the head of the compressor on this particular one. Does that sound about right? Cummins sells a Head kit for it, but it is a little costly, $570, new not rebuilt. The reason I'm asking is that heavyhaulerss mentioned that they had the unloader for $12. So I don't want to spend all that money if I don't have to. Also, I looked today all up and down the air system and could not find anything wrong. The governor is remote mounted on the Volvos and it is doing its job. Also, when I noticed it not building air pressure, I tapped on the head of the compressor and it would kick in and start building pressure again.

Blanco - Lawrenceville, GA, thank you. Hopefully I'll find the cause... Either way, most likely I'm leaning towards the head for the compressor, its the only thing left

Btw, thank you everyone for the replies.

 

Do you have the tag # from the compressor or know the Mfg and model? Many Bendix compressors have a cover plate on the head to access the unloader. For that kind of money just go buy a Reman compressor.

 

Yes you have to replace the complete cylinder head for the unloader on those compressors. You will have to pull the compressor to do it and there is also a critcal torque sequence that must be followed with torque turn method. Not that hard to do but at least a three hour job you might want to price out a complete compressor depending on the milage it might be the wiser choice.

 

if you have to remove the entire compressor, you might as well replace the whole thing while it is out, rather than doing it later down the road.

 

Well, the thing is that I only have 260,000 miles on the truck. I had another volvo (2005) that I sold a few months ago and it has 1mil+ miles on it and the compressor is still strong. I would hate to get rid of the compressor at these miles and put in a rebuilt one. Btw, I've called around a few places here in Atlanta and the best price I got for a reman compressor was $923.00.

 

At those miles I would just put a head on it.

 

Agreed...just put on a new head.

BTW, what year is the truck??? Sure it's not something covered under the warranty?

 

I'd say grease-carbon buildup in the exhaust line 1st. They ae a simple piece of equipment but have trouble and they can be a bear.