Skip to main content ↑ ↓
Topic: Thomas 4101 Compressor Rebuilding (Read 659 times) previous topic - next topic

Thomas 4101 Compressor Rebuilding

I just got done rebuilding my compressor and i would like to walk you trough the steps since in the literature that is available it does not address everything.
tools needed
Major rebuild kit
4 new cylindrical  vibration isolators
8 inch of intake air hose
1 Pan Philips  stainless 10-32 screw 1 1/2 long
4  5/16 nuts tread 18
few washers for spacing
1/4  sockets 1 inch and 2 inch
scraper knife
sharpie
camera
Electrical tape
3 arm pulley puller
Adjustable wrench
Philips screw driver


When you rebuild your  compressor its best if you remove the compressor from the motorhome and work on it on a bench.
Before you start make sure you have the major rebuild kit
( https://www.zoro.com/zoro-select-major-service-kit-630-c87866-p/i/G6206575/)
and 4 new cylidrical vibration isolators
(https://www.grainger.com/product/2NPE9?RIID=67164639335&GID=_NULL_&mid=&gucid=EMT::SKU:CSM-348&emcid=NA:SKU)
and 4 nuts Thread Size 5/16-18 from your hardware store
First take some pictures of the compressor and the wiring it will help later if you forget something.
-Disconnect the 2 dc wires and cover the terminals with duct tape to prevent any shorts and remove the 7.5 amp fuse to prevent the compressor from coming on.
Take a marker and mark the right side of the compressor remember that is the intake side
-Disconnect the air supply lines:the one on the right is no pressure and you will need to cut and replace,the one on the left is a pressure line and it easily disconnects by turning the nut.
at this time try to remove the bolts securing the compressor to the rubber mounts. if they turn excessively and it not possible to remove the top bolts do the following. Also its impossible to grip the small metal flange that the mounts have at the top and bottom to hold it ,while from the bottom you can use a 1/2 wrench to remove them.
-Cut the rubber  mounts at the base(a hack saw or and electric cutter will do it fast)
-If you cut the rubber mounts and was not able to remove the bolt securing the compressor to the mounts do the following.
1. Cut the rubber of the mount
2. Using a Chanel lock or a set of pliers  while holding the metal flange remove the top bolt and save the bolt and the 2 washers.

At this time the compressor is out of the bay
Unscrew  the 4 Allen bolts that hold the piston housing but do not remove them yet: Put 2 pieces of duct tape on each side of the piston housing so it will keep together when you remove it.( this will allow you to keep  the metal plates in order) and just put to the side. Set it down with the piston housing first and make 2 sharpie lines across all plates. when you remove it will expose the piston.
Remove the fan housing which is attached by 4 flat screws.
at this time you should see the piston and the fan blades.
Remove the bolt holding the fan blades and put aside.

Removing the piston and counter balance
https://www.harborfreight.com/8-in-three-jaw-gear-puller-69224.html?ccdenc=eyJjb2RlIjoiODU2MjI4OTkiLCJza3UiOiI2OTIyNCIsImlzIjoiMTguNjkxNDk5OTk5OTk5OTk4In0%3D&utm_source=google&utm_medium=cpc&utm_campaign=19558004081&campaignid=19558004081&utm_content=140367405090&adsetid=140367405090&product=69224&store=&gclid=CjwKCAiAwomeBhBWEiwAM43YICpWNP2BKBfUuA40eiMSkRNzMKNOPMZXs1MCY-fUpFTTMWlGFqI4RRoCLWsQAvD_BwE

Take a picture of the  piston and counter weight and pay attention to the position of the 2.
also take a sharpie and make a mark on the motor side  on the counter weight outlining the area that does not come in contact with the piston and another mark on the fan side area on the base of the piston as well. this will allow you to correctly position the counter weight when you assemble it again.

For this you will need a 3 claw puller (rent one for free from you local auto store)that has long tips to grab the piston from the bearing and not from the piston ring(it will crack the aluminum ring)
As you pull, it will pull the bearing of it base along with the counter weight keep going
Once those are out pull the bearing base.
Caution-the counter weight and the bearing base are offset and it will require you to reset the puller several times so just be patient.
once everything is out locate the metal shim securing the  bearing and counter weight to the axle and save.
there is a stopper ring behind the piston bearing -save.

Installing the Piston.
for this you will need a  Pan head stainless  steel machine screw 10-32  1 1/2 long with a Philips head and a  1/4 socket  big enough to go over the axle and a few nuts that you will use as spacers.
use the fan screw housing to push the piston in.

before you proceed make sure that the counter weight ( usually  has a  grime  mark on the side it touched the piston bearing that allows you to correctly install it )and the piston are going to be inserted correctly.
Caution if you mess this up and have to pull the piston ring out  you will damage the piston ring( thin aluminum and it snaps like  a twig) and it will set you back another 5 weeks till your replacement parts arrive  from China.

Pushing the piston in.

Make sure the stopper ring is in place
Align the the piston shim cutout with the flat axle.

Using the Pan head screw and a 1/4 inch socket push the piston in by tightening the screw using the fan blade screw  housing(it only has about 1/2 inch of travel it will require you to undo and add spacer washers).
Secure the Axle with an adjustable wrench to prevent the axle from rotating when inserting the piston.
you may need a 2 inch socket when the piston is close to its stopper ring
Once the  piston bearing has been fully inserted all the way to the stopper ring insert the metal safety shim for the piston and do not fully insert the shim under the piston assembly .Remember this shim is for the piston and the counter weight.
and do the same with the counter weight.
when the counter weight  getting close to the shim ( Which should be sticking out from under the  piston about 1/4 inch ) align and proceed pushing the counter weight all the way until it touches the piston assembly)
You can also push the piston in by using a hammer and a socket  to tap it in( more like hit it till it goes in)

Now the piston assembly  ,the counter weight and the shim are all in their respective position.

Now it time to put it back together using the new parts

the piston housing is composed of 7 pieces
Piston housing
Seal
Thin metal plate
thick metal plate
thin metal plate
Seal
outer casing

remember i asked you tape  the piston housing .now take the sharpie and make 2 marks  that stretch across all this plates.
the idea here is to keep the 3 middle plates together so you know how to arrange them when you use the new parts.
I have a diagram that i got with a new motor and  either i cant read it or they show it wrong but the plates on the diagram do not make sense when compared with the markings on the plates that i pulled from my compressor.
there are 2 seals that will need to be removed because you will use the new ones.
With the piston housing sitting on the table remove the tape and the Allen bolts.
holding it from the middle pull up the top outer casing.
If you see a seal good job if you see a thin metal plate remove it and put it back on the stack where the rest of the plates are the same way.
Clean the seal (scrape)
now take a picture of the thin metal plate assuming you did not move it or it in it original position.  (it has a chess pawn cutout and a hole and it should have the  seal mark on it as well.
keep the 3 plates together
the piston housing has a hole 1/3 midway  as it sits on the table try to relate the position of the hole with  position of the seal and the 3 plates  with the mark of the air flow that you made on the outer casing before you opened the piston housing.
All i am trying is to make sure you put it back together  as it was before.
Scrape the seal from the piston housing.
now its time to put it back together.

Put them in the same order as found thin paper seal on the piston housing and thicker seal on the outer casing.
the rubber  seal and the spring that come you have you do not need.
put the 2 springs and plastic seal on the piston ring and the dark seal on the piston body.

here it a little tricky.
start with the first piston ring  while you hold it together in place  slide the piston housing over the first one then the second one and then you add the dark piston body seal and push it all the way in and then add the fan housing and  tighten the Allen bolts  once that is done tighten the flat head fan housing bolts as well.

now if all is good  and put together correctly  you should be able to blow air freely  into the air intake hole  but not suck air, the thin blade should block it if installed correctly.
When you blow trough the intake it should make a sound as well.

Now take the compressor back to the motorhome to reinstall.
you will need to remove the 4 bolts holding the compressor base to the frame in order to install the rubber isolators.
Clean the 4 bolts that have secured the compressor to the mounts. they have used a tread lock  that will prevent the bolts to tighten all the way
Once the isolators are secured to the plate secure the plate back with the 4 screws and secure the compressor to the mounts.
Be sure that the compressor is tight to the mounts and there is no play.

reconnect the wires
reinsert the fuse
Enjoy
 I hope this helps.
Daniel
 
 





2003 Foretravel u320 build 6066
cummins 450 ism
2008 Jeep Cherokee Toad
former Country Coach Owner.
Part time Rv er
Never afraid to learn.

Re: Thomas 4101 Compressor Rebuilding

Reply #1 –
I have a newer thomas 270025 pump.  I noticed there are only two through bolts both on the street side. The two on the curb side appear as though the rubber mounts were at one point attached to the mount but are no longer. 

Not sure why this is but I want to through bolt these two.  Have not put the inspection camera under the mount but is there anything under there that would prevent through bolting ?


2003 U320 40 AGDS Build 6157 161K miles

Hampstead NC

Re: Thomas 4101 Compressor Rebuilding

Reply #2 –
Daniel I just ordered the major rebuild kit for my Thomas compressor. On Friday I was at HWH and the compressor definitely is not putting out more than 40 psi. They had new ones but they were $800 plus the time to put it in so I'm going to pass on the new one and rebuild. I appreciate your extensive post on how to rebuild it.
It was backed ordered on 0 for quite a while but they are now shipping I believe. There was also a guy on eBay that had them but I was going to pass on that. They checked my system for leaks while at HWH and they didn't find any that I was very surprised about. When he pulled the computer there were several parts on the motherboard that looked like they were about to fail or had been failing so they took it off to the repair shop and replace those components. They also put a new acrylic bowl on the dryer total cost I think was about $550 in that included a free overnight stay in their parking lot. I'll let you know how it goes.
By the way if you took any pictures of the rebuild I would appreciate it if you could post some of them thanks.
Bob
'99 U320 40 WTFE
Build #5462,
1500 Watts Solar 600 amp Victron lithium
2012 Jeep Grand Cherokee Overland Hemi
Instagram bobfnbw
Retired

Re: Thomas 4101 Compressor Rebuilding

Reply #3 –
If you need just the compressor, they are available for about $450, but you'll need to reuse your base, mounting hardware, etc.

https://www.google.com/aclk?sa=l&ai=DChcSEwi9r7nx6OeBAxXQ_eMHHUnkCTYYABAMGgJ5bQ&gclid=Cj0KCQjwpompBhDZARIsAFD_Fp-DJqiQiI_g5qOuKECSRSijH8y8IZj-fE7c0mrO0WVFyYo2gbA1X1caAqnVEALw_wcB&cit=CkQKCAjwpompBhAMEjQAhu3lJsvMUkQy1anRSxN0h_Q7mvmnZI3v_1iQ8kVFsQIuPk2WKcOY0cB9LmKk8EFV6peXGgLLKPD_BwE&sig=AOD64_2sXREztP5OP-yNLO6klRxwqNRoQA&ctype=5&q=&ved=2ahUKEwjg0rHx6OeBAxXcm4kEHZk1ArMQwg8oAHoECAEQDA&adurl=
Mark & Bev
2001 U295 36' Slide
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: Thomas 4101 Compressor Rebuilding

Reply #4 –
What year did they change the size of the compressor?
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Thomas 4101 Compressor Rebuilding

Reply #5 –
Quote from: MarkC –
If you need just the compressor, they are available for about $450, but you'll need to reuse your base, mounting hardware, etc.

Well for just a little bit more that sounds like a really good deal. Especially since the rebuild kits on backorder thanks for that.
'99 U320 40 WTFE
Build #5462,
1500 Watts Solar 600 amp Victron lithium
2012 Jeep Grand Cherokee Overland Hemi
Instagram bobfnbw
Retired

Re: Thomas 4101 Compressor Rebuilding

Reply #6 –
Quote from: MarkC –
If you need just the compressor, they are available for about $450, but you'll need to reuse your base, mounting hardware, etc.

https://www.google.com/aclk?sa=l&ai=DChcSEwi9r7nx6OeBAxXQ_eMHHUnkCTYYABAMGgJ5bQ&gclid=Cj0KCQjwpompBhDZARIsAFD_Fp-DJqiQiI_g5qOuKECSRSijH8y8IZj-fE7c0mrO0WVFyYo2gbA1X1caAqnVEALw_wcB&cit=CkQKCAjwpompBhAMEjQAhu3lJsvMUkQy1anRSxN0h_Q7mvmnZI3v_1iQ8kVFsQIuPk2WKcOY0cB9LmKk8EFV6peXGgLLKPD_BwE&sig=AOD64_2sXREztP5OP-yNLO6klRxwqNRoQA&ctype=5&q=&ved=2ahUKEwjg0rHx6OeBAxXcm4kEHZk1ArMQwg8oAHoECAEQDA&adurl=

I just gotta ask.....if a new one is $415, why would anyone spend  near that amount to rebuild an old one?
Mike in AL
2001 U295
8.3 ISC 350
Build 5918

Re: Thomas 4101 Compressor Rebuilding

Reply #7 –
Quote from: mkc1962 –
I just gotta ask.....if a new one is $415, why would anyone spend  near that amount to rebuild an old one?

Complete rebuild is much cheaper.

https://www.zoro.com/thomas-service-kit-for-5z349-sk405dcmaj/i/G0352746/?recommended=true
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Thomas 4101 Compressor Rebuilding

Reply #8 –
Actually the rebuild kit is only marginally cheaper. When I first purchased the major rebuild and it was on backorder they sent me a 20% off coupon. When I added the compressor and I forgot about that 20% off coupon, but they called me a few days ago asking me about the delivery address and canceling the other order of the major rebuild kit. That's when I asked her if they would honor the 20% off and she did so I actually got the new compressor for less than the cost of the rebuild kit. $361.50 total with shipping and tax.
The only difference is it doesn't have the slash D after the model number and it doesn't have the air intake in the front in fact I'm not really sure where the air intake is. Maybe somebody can fill me in on this. There's two exits at the top and they give you a plug for one of them and there is a round opening on the left side just like on the original only this one has a fiber filter type plug on it I'm wondering if this is a over pressure release? But on my original the intake was on the front and on this one it does not have a hole for the intake. Puzzling.
'99 U320 40 WTFE
Build #5462,
1500 Watts Solar 600 amp Victron lithium
2012 Jeep Grand Cherokee Overland Hemi
Instagram bobfnbw
Retired
 

Re: Thomas 4101 Compressor Rebuilding

Reply #9 –
That round felt is the air filter and that is the air intake location. 
Mark & Bev
2001 U295 36' Slide
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad