Air Suspension
Compressor Rebuild
Introduction
Rebuild Principles
Parts Needed
Rebuild Procedure
Parts Sources
General Comments
More Information
Photo:
View of EAS compressor from 4.0/4.6 model with enclosure cover removed.
Compressor for
Classic EAS models looks similar (see photo below) but has inlet on
lower pump body opposite exhaust and different has mounts for
underbody
mounting.
Introduction
As mentioned on the Air Compressor Diagnosis
and Replacement page, the RR air compressor is a sturdy industrial
1/5
horsepower 20 amp "Wobl" piston unit made by Thomas Pumps, one of the
best-known manufacturers in the world. When it wears out, usually in
the 120-150K mile range, it usually gets very noisy which indicates the
piston, cylinder liner and seals are worn out. Replacement of the unit
is easy and is covered on the aforementioned page. Rebuild kits are now
readily available from Rover Renovations
for about $100, and they even sell rebuilt compressors for aboout $240.
Most of the information on this page was compiled before such
convenient sources were available, and we heartily thank fellow RR
enthusiast Dennis Altman for using the information to establish Rover Renovations
in order to make such parts so readily accessible to Range Rover owners!
Rebuild Principles
If you do not wish to replace the entire compressor you can have the it
rebuilt by a Thomas Pumps rebuilder. For example, Abe
Thietten of Austria took his genuine compressor (which was still
running,
but without any pressure) apart and found that only
the Teflon piston ring was worn out. Thomas pumps in Germany offered to
repair it, with a minimum value for repair orders of €80 --
i.e. US$100.
Another option is to order parts to rebuild it yourself.
Genuine Thomas rebuild kits are now available from Airbag
Man in
Australia (see photo at right).
The kits consist of the piston and sleeve as well as the crank,
replacing all the likely wear parts. A new low cost source for the same
items in
the US is Rover
Renovations.
When
Jeffrey Johnson bought his 95
Classic, the EAS pump was
really shot,
making tons of noise. His first attempt to replace it was a "rebuilt"
unit
off eBay; however it too made noise and Jeff says "I now know it really
wasn't
rebuilt but rather cleaned and painted".
He got tired
of buying
used compressors (which he found were usually worn and noisy) for his
95 Classic and decided to try a rebuild. After obtaining the parts
(piston, cylinder and crank set up), he tried them on his oldest
compressor (which was very noisy) and took
over 8 minutes to refill the air from access to standard height.
After installing the new parts, the compressor could fill the
system sufficiently to go from access to standard height in less than 2 1/2 minutes, and noticed the
compressor was now so quiet he can't really hear it run over the normal engine noise.
After pulling one of these compressors apart, Jeff was as impressed as
I
have been with their quality and believes these compressors could
very
well last through 2 or 3 rebuilds of the
compressor parts. The
remainder of this page covers the rebuild operation once you have
removed the compressor from the vehicle as described on the Compressor Diagnosis and Replacement page.
Parts Needed
Classic Air Suspended Models:
After
doing research on the different models, we found the one used in the
Range Rover is a variant of their 315CDC5612 (see compressor diagnosis
and replacement page).
For the Classic, the stock 315CDC5612 seems to be an almost exact
replica. The only difference is that the standard 315CDC compressor
head has 1/8" pipe thread for
both the intake and output ports but the old style RR version has 1/4" in and 1/8" out
for some reason. However this does not affect the rebuild procedure.
Rebuilt parts for the Classic compressor are as follows:
Thomas Part # 666477 Cylinder liner and piston assembly
Thomas Part # 623557 O Ring for top of cylinder
Thomas Part # 623615 O Ring for exhaust valve
Picture at right: Thomas 315CDC5612 compressor modified with
intake filter (2) moved upwards so the unit will fit in P38 model; on
the
standard version used in the Classic the filter is mounted on the
lower left opposite the exhaust.
Jeffrey Johnson reports "The main
part needed is Thomas part # 666477 -- this is the
piston and connector rod (all one piece)
with a new teflon seal and the crank counter weight with a new
sealed bearing and a new
aluminum cylinder -- these are the parts that wear out and make noise. My original one has
a deep groove in the cylinder where the
piston slapped against it, the teflon ring is nearly gone and the crank bearing is all sloppy. The
other parts I got were an O ring #623557
$1.58 for the top of the cylinder and a small one #623615 $6.10 for the exhaust valve. The other
parts didn't have any wear to speak of and
the reeds for the valves are stainless steel that I just cleaned with fine steel wool and put back on.
The total cost of the parts was US$71.77 to rebuild one compressor".
See Parts Sources section below for sources for
these parts.
Range Rover 4.0/4.6/P38:
We are not certain if the same part numbers apply to the 4.0/4.6/p38;
the new style uses a
different intake and valve system and the piston ring may be different since the ring acts as the intake
valve. The way the intake is mounted on the end plate is also different from any standard
Thomas unit Jeff or I have found so far. The cylinder head of the p38
unit has two holes to get air from the crank
case, whereas the stock Thomas 315 has not. An old style compressor
will work in a
P38 with adaptation (see compressor replacement page) but it is
uncertain whether the internal parts are the same to allow a new style to be rebuilt using these
parts.
I recently discovered that complete
Thomas compressor service kits are available for the 4.0/4.6
compressor. The kits include new sleeve
and inston/conrod assy, for about US$150. See Parts Sources section below.
Rebuild Procedure
Jeffrey Johnson reports the
following details of the procedure he used on his Classic compressor:
"Remove the end plate and
small screw plug on the side of the crank case, then turn the crank till the center of the offset weight
aligns with the plug hole and the set
screw for the crank can be accessed, there is a hole drilled in the counter weight with a screw in it.
Then turn the crank to collapse the piston
and work the crank off the motor shaft and remove it out the lower opening. The cylinder is just a
floating type with a lip that fits into the
groove of the head where the O ring is.
"The only thing that takes time is for the O ring in the exhaust valve which needs to be glued into it's
seat with high temp silicone gasket maker,
I tried to just dry fit it in the seat and it came out once the compressor ran a bit. I probably
could have got by without replacing the
valve O ring but didn't want to risk it. Aside from this, it only
takes about 5 minutes to replace all the
parts!"
While you are working on the compressor, you can open the back end of
the motor to check the brushes, but Jeff
found that even on his very worn out compressor the brushes were less
than 25% worn, and there was plenty of left in them. (For advice on how
to replace motor brushes at very low cost, see the secction on starter
motor brush replacement). Jeff found the motor
bearing was still good but he injected a little grease in it just to be safe. The closed end of the motor
just has a bushing. If that is worn a
starter rebuild shop could probably repair it but Jeff found his was
still fine.
Jeff reports: "It's been a few days now and it's quieter than ever,
seems to have
settled in or something, with the engine running I now have to actually
get out and touch the intake tube to the compressor to feel if it's
running as I can't hear it at all! This is more of what I'd expect for
a vehicle of this class. It's really quite amazing and now I'm happier
then ever I decided to keep and repair the EAS system rather than
convert to coils".
Parts Sources
Classic
Models:
In the US, the compressor parts supply situation has recently
(2006) been transformed with the establishment of Rover Renovations
by fellow RR enthusiast Dennis Altmanecame frustrated at the difficulty
of obtaining other than complete EAS assemblies. Rover Renovations
now sells rebuilt Classic RR compressors for about $220, and compressor
rebuild kits for about $100. The latter contain a Teflon
seal, crank, crank/piston bearing and cylinder. He also sells the
teflon seal separately, as well as the cylinder head to cylinder seal,
the discharge check valve seal, and new brushes for the motor.
Airbag
Man in Australia also sells an inexpensive complete rebuild kit for
the Classic
compressor, including piston, liner and crank, as depicted in the photo
above. Their part number is DRK002.
Jeff Johnson got his parts from a local Thomas Pumps dealer, Combined
Fluid Products Co. in Lake Zurich
IL. The person that handled
his order is:
Cathy Preusse
Combined Fluid Products Co
(847)540-0054 x27
Cathy@combinedfluidproducts.com
Jeff reports that Cathy will take orders via e-mail or phone. She can
also
send an e-mail with a drawing and parts
list plus a spec sheet. They have all the parts available for flapper valves, screws, etc. They
also sell the complete compressor $200 or 30 units for $150 each.
(This compressor is a Thomas model 315CDC56/12
for the 93-95 Classic Rangies where the intake port is on the
head opposite the exhaust port and both valves are in the head). Cathy
has no specific information of RR's use of this
compressor, she only has information on the Thomas line of products and
is a source for end users to buy parts. Airbag
Man in Australia now sells a complete rebuild kit for the Classic
compressor, including piston, liner and crank, as depicted in the photo
above. Their part number is DRK002. Cost is about US$150.
Range Rover 4.0/4.6/P38
The main difference between the P38 compressor
and the Classic one is the different intake valve arrangement. The P38
compressor has
the intake port on the crank cover and the intake valve system and
head are slightly different. However otherwise, the same parts are
used.
In the US, the best and lowest cost source for the 4.0/4.6 compressor
rebuild kits
is Rover Renovations,
who charge about
$105 for a kit consisting of the Teflon seal,
crank, crank/piston bearing and cylinder. It also includes the O-ring
head seal. Rover Renovations also sells all the other parts of
the compressor, including new brushes for the motor, check valve seals,
rubber mounts, etc. If you want to take the chance of only replacing
the teflon seal (the most likely wear component), they can sell that to
you separately for about $38. If you would prefer to take the easy way
out, they also sell completely rebuilt 4.0/4.6 compressors for about
$240.
For worldwide distribution, I located a source for
complete rebuild kits for the 4.0/4.6 compressors at Airbag
Man.
(See photo of their kit above). They sell a complete Thomas compressor
service kit that includes new
sleeve
and piston/conrod assy. It sells for A$200.00
or about US$150. They are located in Brisbane, Australia and ship
worldwide. They also sell the complete (new) 4.0/4.6 compressor for
US$300.
More
Information
Airbag
Man
EAS compressor rebuild kits, emergency bypass kits; worldwide shipping.
Air Suspension Information, Diagnosis and
Field Repair page.
Range
Rover Parts Sources page (look under "suspension")
Rover Renovations
US supplier of new & rebuilt EAS parts and rebuild kits
including compressor rebuild kits.
Please email me if you
have experience with getting these pumps repaired or rebuilt
so we can share your experience with others.
Last
Updated April 2007