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Topic: Washer pump replacement 75-79 C3 how to do..

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Washer pump replacement 75-79 C3 how to do.. (1/4)
 10/25/15 1:19pm
jim in oregon
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Milwaukie, OR - USA

'78 Silver Anniversary T Top coupe,58k orig miles. THM350 auto, 350 L48, JBM headers,Oyster White interior,.as of Nov '15 in process of painting.

Joined: 10/19/2015
Posts: 71

Good  morning from Oregon..

Please READ THRU THIS COMPLETELY before starting this task..:(...:)

 I recently replaced the windshield washer pump-filter on my 78 C3 with tilt/tele steering, cruise control.
This was one of those small things I have worked on to get fixed after most of the big things had been done.
Among those big things were the complete brake job including new master cylinder et al.

Windshield washer wasn't working.
I had filled the washer bottle  jar and neither it nor the separate  filler neck were  leaking, old pump was getting power..but not doing anything..
All water lines from jar to windshield wipers were intact. 

Pump was simply dead from sitting much of it's 37 years before I got the car.

SO, Anyhow, THIS  thread describes how I successfully replaced the pump-filter WITHOUT  removing the washer jar-bottle...or the brake master cylinder and brake vac booster or cable to cruise-speedo..or anti theft horn, or vacuum canister, or fender..

Sort of a magician's trick on the 75-79 C3 Corvettes that have the washer jar tucked down and under the driver's side front fender...

First, The best time to replace the washer jar is during replacement-removal of the brake master cylinder.My brakes were already done and I didn't want to do all that stuff over.

Second, unless the washer jar is damaged..(unless you want new), use the old jar after you clean it.

This thread is my 'how to' attempt to help others for replacing the washer pump and filter nut when washer isn't working and associated components ARE working and intact.
I wore good neoprene well fitting shop-work gloves and a long sleeved shirt because it can be rough on hands and wrists due to tight space working.My hands are pretty large, and I have some arthritis..but even small hands may have problems.

The washer pump is available from most of the Corvette after market folk as is the filter-nut, ( or bottle-jar and neck extension etc.
Quite probably the GM pump-filter/nut are available still for the purist.
I bought pump and filter-nut from the big "E" outfit for around 40.00 or so.
Pump & filter nut are the same for 75-91 Corvettes( and probably many GM vehicles of similar vintage)
Washer Jar-bottle and neck extension are specific for 75-79 Corvettes.

1.IF your washer bottle has fluid in it, drain it.You can access the rubber water line hose VIA the driver's side fender louver and use a thin straight blade screwdriver to gently slide the hose off the pump fitting..Put a pan under the car to catch the fluid if indoors.
IF the bottle is dirty inside, fill with hot soapy water and use a small brush on a stick to swirl around inside the bottle to clean it up best you can..

2.Using a socket with 4" extension, loosen and remove the 10 mm sheet metal bolt that holds the filler neck to the side of the fender..Take care to not drop the bolt of course.

3.Using a socket with about an 8" extension remove the 10 mm sheet metal bolt that secures the bottle on the manifold side upper of the bottle..

4.Gently twist and pull the filler neck extension upward from the washer bottle and set aside. It has some ridges on it that help secure and seal it into the jar-bottle below but there's no special orientation of the filler next extension for removal or installation..

5.Loosen and remove the 1/2" nut & washer from the stud that secures the metal strap holding all the bundled  wires and vac-water line from the cowling next to the hood latch.
Pull the whole wiring cable hose affair backwards gently 3-6" and get it out of the way.

   Now the funner parts..:)

6.You'll need about a 10" extension and the 10 mm socket for removal of the third and last sheet metal bolt holding the bottle in place.
This bolt is concealed behind the bottle and attaches to a threaded hole in the inner fender..It is on the same plane as the front bolt you last removed and the washer bottle has an indentation behind it that enables you to get the socket-extension back there to access the bolt head. You can't see it nor feel it with your hands.

A trick to avoid losing the bolt once loosened is to take a small grape sized piece of plumber's putty and put it in the bottom of the socket so that the bolt head makes contact with the soft putty and hopefully doesn't fall out of the socket once you have it undone and are removing( or installing) it in a  location that is hard to access or where dropped stuff drops into the abyss below..:(..Use one of the 10 mm bolts you removed to try this out until you have sufficient plumbers putty in the socket to hold onto the bolt head..)

7.The water bottle is freed up with the exception of the electrical connection to the two .250 male tabs on the pump motor.
Don't disconnect the electrical connection yet  

 Now to remove the old washer pump/motor and interior filter-nut.
The pump has a threaded male connection that is inserted-removed thru the washer jar bottom .It has a thick rubber gasket-washer ( about 3/16" thick)
The pump is secured from the inside of the washer jar bottle by the filter-nut integral assembly. It's a pressure fitting, no sealant on threads or RTV .

8. To remove the old pump and interior filter-nut, you'll use about a 10" extension and a DEEP 7/8" socket inserted thru the top of the washer bottle jar and down to the bottom over the cone shaped filter and onto the black plastic 7/8"nut.
There are two extension 'ears' on the washer jar-bottle that go downward and sort of hold the pump to keep it from rotating as one loosens the interior filter-nut connection.
Once the filter nut is loosened up, try to pull it upward and out of the bottle with the socket and extension ..but you'll probably NOT be successful and will have to fish it out of the bottle with a wire.

Now the pump is free  except for the wire connection so rotate the bottle so the bottom of the bottle is  oriented with pump facing toward the windshield.... Mine had a black connector for both wires but it was damaged and corroded..

You will need to carefully change the orientation of the washer jar so it is rotated and the pump and jar bottom are oriented so they are accessible on the cowling-windshield side of the car..and access is still awkward and tight.
BEFORE you remove the electrical connection to the old pump, make a note of WHICH of the pump terminals has the RED power wire attached.
Take your new pump and put some sort of red magic marker mark on that male terminal of the new pump.

I couldn't find a replacement connector readily so I elected to cut the old connector off, stripped the red hot wire and the ground wire and installed quality crimp on .250 female connectors to each with shrink tube applied over the connections to help with strength and resistance to road splash.

AT THIS POINT, I did a small engineering modification to the washer jar that was simple, invisible once the washer jar is installed, and allowed me to reinstall the washer jar 10 mm bolt MUCH easier. 

The fender side rear washer jar flange for mounting is a hole in the flange...like the hole for mounting on the manifold side...Not so tough to get to in order to remove the bolt, but really tough to get to to re install that 10 mm bolt blind and try to have water jar aligned-positioned so the receiving hole in fender accepts the 10 mm sheet metal bolt..

With a torch, I heated up a 3/16" diameter awl and turned the fender side rear hole in the water jar into a SLOTTED ENTRY rather than a hole.

The hot 3/16"-1/4" metal will melt thru the flange on the water jar fast and cleanly..You can use an old thin blade screwdriver or any suitable diameter piece of steel.Take your time to do this .

 Now for the install of the new pump with filter-nut. 

Before installation, I checked the new pump to see if it operated by applying 12 volts DC and a ground
BRIEFLY and felt the pump running.
OR you can trust the new pump will be good and install without checking..A 12 volt DC battery like a lantern battery works fine for this

9. To hold the filter and nut in the 7/8" deep socket, I applied  a thin strip of the plumber's putty on the leading edge and 1/8" up on the inside of the 7/8" deep socket.I experimented a bit to get the smallest amount that would  allow the socket to fit the nut yet enough to hold onto the filter and nut.

I didn't want to apply this to the nut itself because then it'd have stayed on the nut and possibly over time ended up messing up the pump or filter in the system.

10.Next step was to re-install the water line hose to the connection on the new pump and attach the two electrical connections to the pump...I clipped about one inch from the water line hose so the new connection had hose attached that hadn't been stretched for 37 years.

I used a couple of 1/2" by 4" duct tape strips to hold the pump in place in the washer jar bottom.

Then With pump fitted, I held the pump with left hand and inserted filter nut with right hand and deep socket with extension down thru top of water jar..This was done with water jar just slightly canted top right so I could keep everything together for the process.

Took a bit to get/keep pump flange inserted straight thru hole in bottom of washer jar and to get the filter-nut to start threading on properly but got it done and cinched down snugly..but not ham fisted tight.It's NOT a water pressure connection..just a good snug water seal..

11.   Now I inserted the rear 10 mm sheet metal bolt into the mounting hole bracket on the fender and tightened it up so there was a bit more  than the thickness of the water jar mounting flange yet to be tightened on that bolt.IE:left about 3/8" of bolt yet to be tightened.

12.Next was to orient water jar with attached pump, water line and electrical connections so it was ready to slip into place with rear NOW slotted mounting in water jar..

I got it in place, using an awl inserted thru water bottle manifold side hole into mounting bracket and levering the bottle toward the fender until it fitted snugly in place over the partially tightened fender side 10  mm  bolt. 

Then I tightened up rear bolt while keeping water jar positioned with the awl-punch and then removed awl and inserted and tightened manifold side 10 mm bolt.

13.Then the water bottle extension-neck was inserted and pressed downward firmly until it was fully seated in the top of the water jar.
Attached extension-neck with last 10 mm bolt to small attachment bracket on inner fender..

14.Re attached wire bundle/hose bundle to stud on top of cowling near hood latch..

15.Filled water jar with windshield wash solution.

16.Tested washer..:)

Checked for all tools accounted for..everything buttoned back up properly..

Some might simply accept that their windshield washer wasn't working..
In Oregon, we get rain quite often and being able to see thru clean glass has always been important for us here.
Plus, I like for all systems to  work properly..

Have fun with this..
Before I quit drinking beer years ago...this would be classified as a "12 pack job"..:)Jim in oregon

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Re: Washer pump replacement 75-79 C3 how to do.. (2/4)
 11/10/22 1:40pm
Former Member

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, TX - USA

1979 Coupe, Metalic Blue, L48, Automatic, Numbers Matching,

Joined: 8/16/2022
Posts: 2

Jim this is a fantastic description of the process. Thanks Bobby D in Houston. Restoring one owner 105K miles 1979 Dark Metalic Blue Matching Numbers.

Re: Washer pump replacement 75-79 C3 how to do.. (3/4)
 8/8/23 2:54pm
Limited Member
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Joined: 8/8/2023
Posts: 1

Thanks - this is extremely helpful!  
The washer tank can be pretty easily removed which makes this a lot easier. To do so, you will need to remove the triangular panel on the undercarriage right  behind the wheel. This panel is held on by four 1/2” bolts, two which are visible and two of which are concealed behind the rocker panel trim molding. 
With panel removed, the EFE canister can be removed and discarded. Now the pump tank will drop right out and can be worked on while on the bench

|UPDATED|8/8/2023 12:54:33 PM (AZT)|/UPDATED|
Re: Washer pump replacement 75-79 C3 how to do.. (4/4)
 8/9/23 11:04am
Former Member

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, TX - USA

1979 Coupe, Metalic Blue, L48, Automatic, Numbers Matching,

Joined: 8/16/2022
Posts: 2

Well done. I am interested in more inciteful presentations. 


One note! I found it easier to use a Battery Charger to get 12 volt test DC Current. 


Best Regards

Bob Downes, (281) 222-2860, bob.downes@earthlink.net

Restoring a 1979 Coupe, found in an Estate sale, that had not bees started in 15 years, 2-1/2 years ago. Getting close to being able to drive for the first time. It is Matching numbers, One Ownes, and no apparent accidents. 105K miles. Metalic Blue with Black Interior.

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