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those with C4's and 965's have a high pressure hydrarulic pump, C2's do not.
Basically the unit is composed of a pressure switch, a dc motor and a pump.
if its not leaking, to check the pressure switch- the bottom pins are 1-2-3, the top 4-5. there should be continuity between pins 1-2-4, and no continuity between 3-5
if the pump is leaking its going to be either from the gasket between the pump and the motor or the shaft seal inside the pump. The pump also has a hard brake line fitting on top and a soft line going into the front of the unit. If the hard line leaks at the pump you may be able to just tighten it. The soft line has an O ring in it going into the pump.
Ok moving on to the money shot, the motor and pump. if yours goes bad there seems to be a few options
1) find a new one $3700+
2) send it away to be rebuilt $1800+ (if this is what you elect to do I'd suggest getting a brakedown of all the replaced parts, I'd even want pics)
3) find a used unit / price unk (great but its still going to be a 30+ years old part)
4) retro fit one from a mid 90's XJ6 Jag around $250 (Still a 30 years old part)
5) rebuild it yourself, yep yourself
The motor is comprised of a housing, an armature with a commutator. The communtaor is copper and will probably be worn pretty thin, so that should be replaced. Two brushes spin around the commutator, they should be replaced. There is a rotary shaft seal that the armature shaft goes through to spin the pump. This is the part that was leaking on mine. There is also a filter/ basket inside the pump that has an O ring but I doubt that would cause a leak.
Taking the unit off the car is pretty easy, just have to make sure its not under pressure and have a sh*tload of shop towels or rags to wipe up all the brake fluid.
The motor can be rebuilt by a good amrmature shop, but finding one that works on this small of a motor may be difficult. I found a guy in Chicago to rebuilt mine, Im in VA and have no relationship with this shop other than he did a good job for a fair price. The shop is Quality Armature Inc 773-622-3951. They put in a new armature, commutator and brushes for under $300. Thats a damn good deal in my book. Again, no afilliation just a satisfied customer giving you an option.
O rings, gaskets and that unicorn shaft seal- Rubber exposed to DOT3-4 brake fluid should be either EPDM or SBR. I didnt change out any O rings but did buy some flat rubber and made a new motor-pump gasket. I bought sheet rubber from McMaster-Carr. The shaft seal is a TC profile 8x16x5.5mm EPDM rotary shaft seal, that no one on the planet stocks and I know because I called them all. After scouring the globe (CONUS and OCONUS) for this seal I finally realized if I needed one I had to have one manufactered. I had 50 made, that was the smallest min order I could get from a manufacture. I'm keeping 6 and I'll sell the rest.
Bottomline- if yours is/goes TU you can and should rebuild it yourself. this is an easy one
pressure switch-green, pump-gold, motor-black
pump- flat gasket, filter, O ring and key (silver thing)
motor, armature, seal
the motors shaft fits in that key and spins within the filter
motor shaft, it fits in the key
where the shaft seal goes
with a new seal
refer to Adrians book or other posts to bleed the system. thats all i got...
08-01-2022 | 04:38 PM
C4 high pressure hydraulic pump rebuild
