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Sport Seat Lumbar Pump Repairs

  • Thread starter Steel Half-Shafts
  • Start date

Steel Half-Shafts

I just completed repairing my Passenger Side Sport Seat Lumbar Pump which recently failed on my 1990 ZR-1.

Here's a rundown on what I found and how I repaired it for those who are interested:

-Remove the bottom seat cushion. There’s a small wire retaining clip at the bottom-front of the seat. Push down on the seat cushion and flip the clip inward towards the rear of the seat. Lift the seat cushion up to reveal the lumbar pump with 3 small clear tubes attached to it. You might want to prop the seat cushion up and out of the way.

-At the rear of the pump you’ll see two very small Phillips head screws which secure the retaining plate for the pump diaphragm assembly. You must remove both screws along with the retaining plate. Use a very small Phillips head screwdriver for the bottom one as it’s a little hard to get at due to interference from the seat frame. It’s Not necessary to remove the pump.

-Remove the retaining plate and pull the pump diaphragm assembly with the 3 small tubes attached off of the motor operating rod, towards the seat back, and clear of the pump body . I found the diaphragm broken and the plunger had jammed in such a way as to prevent the pump motor from running.

-Carefully remove/pry the 3 small clear tubes off the diaphragm assembly using a flat bladed screwdriver and pulling them clear. I marked the 3 tubes and their location before removing them. They go to the 3 inflatable bladders in the seat back. Take the diaphragm assembly to your work bench.

-The diaphragm assembly is held together with 4 small nuts and bolts. Remove these 4 nuts and bolts and pull apart the assembly revealing the diaphragm and it’s attached plunger. Remove the single screw that attached the diaphragm to the plastic plunger and any pieces of old diaphragm.

-Using the old diaphragm as a pattern, cut a new one out of a pair of heavy duty Rubber Dishwashing Gloves or something similar (1” dia. circle). I used a “Hazmat Glove” from work and a suitable ½ drive Socket to draw the 1” circle. Carefully cut it out, punch a hole in the center of the new diaphragm and replace the plunger and screw with it’s washer using a little silicon sealer in the screw hole to prevent the screw from vibrating loose with use.

-Place the new diaphragm and plunger back in the assembly taking care that the plunger is facing outwards and re-install the 4 nuts and bolts. Slide the assembly back into the pump body making sure you get the plunger back on the motor operating rod. You may need to loosen the 4 bolts a little, and rotate the plunger/diaphragm to align it with the motor rod and allow the rod to pass through the hole in the plunger. Don’t forget to re-tighten them!

-Re-assemble the diaphragm retaining plate with the 2 small screws to the pump body. Be sure to test the pump and make sure it’s inflating the bladders before you replace the seat bottom.

Only took me 1 hour or so to do the repairs and happy to say it works fine again. :dance

Mid-America does sell just the diaphragm sub-assembly (P/N 603-034 for $40) if you don't what to go through the trouble of making your own.
Great info Gordy. I need to do the same repair to both of my seats. Haven't done it yet beacause they're just so darn comfortable :)

Finished rebuilding mine last week, using a heavy duty chemical rubber glove and both of them work great! I removed both of mine before I read your post. Actually I just found this forum last Friday. I had been using "The other Forum".
Welcome To The Corvette Action Center RubynJames!

Welcome to the community that cares for its members Jim. We have a wonderful group of people in our community helping keep this site the best it can be. I'm glad you found us. :upthumbs

_ken :w
I've just discovered one of the plastic extrusions where the clear tubes attach on my '85 has broken off.

From the material on the net, I can't tell whether this part's available separately, as part of the air bladder package or whether it's considered part of the pump itself and only available that way.

Anybody know? Thanks in advance.

The air bladder package (diaphragm sub-assembly P/N 603-034 for $40) that Mid-America sells includes that part with the plastic extrusions as well as 3 new clear tubes. :D
Thanks for both the information and the detailed instructions, Gordy. I expect the installation will be obvious once I get the parts.

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