Steering Rack Disassembly and Refurb

[grannyknot]

2 hours ago, wheee! said:

One more.... what is the purpose of the small plastic plug under the driver side bushing? White in your picture here.

My concern is, I plan to powder coat this part...

It might just be a third point of contact so the rack doesn't slop around in the rack tube, it is probably nylon and probably was longer when new and slow wore down over the miles, just a thought.

[Captain Obvious]

We talked a little bit about those white plastic nubbins a little bit early on in this thread.

My theory is that they have something to do with the fitting and alignment of the two major components of the rack tube. The rack housing body is made up of two parts... 1) A cast iron piece that houses the pinion gear and one end bushing, and 2) a steel tube that reaches over to the other end of the housing. I believe those white plastic nubs are some sort of epoxy used to align and lock the two pieces of the assy together.

I'm thinking that since the alignment of the long steel tube into the cast portion that houses the pinion gear is important, maybe they loosely fit the two parts together, locked them in an alignment jig, and then used a hard setting thermoplastic to lock the two together. Inject it into the hole until it comes out the other side, and then let it cure in place locking the two parts in alignment.

They did similar practice on the 72-on suction piston housings on the carbs, and they also employed that technique on the EFI throttle linkages.

They aren't grease fitting holes. Not only are they too small, but if you look inside the rack tube, there are no holes through. No way for grease to get inside the housing to do anything.

[wheee!]

Well, they melted out in the oven...

[Zed Head]

Then what happened?

Are the holes through-holes or divots?  Any parts get loose?

[wheee!]

I will report back when I get a good look. It was still in the oven cooling when I shut it down tonight.

[Captain Obvious]

Well that's probably not good. I had suggested they were epoxy, but I should have been a little more specific. They are plastic, but I don't know if they are thermoplastic, or thermoset. Sounds like they are thermoplastic...

So how much goop came out? Just tiny dots like what would fill the holes, or once it turned runny, did a large amount come running out of the holes? Like it was melting out of an internal cavity of some kind?

Pics or it didn't happen. 

[Zed Head]

This has probably been noticed before but the 240Z racks are different from 280Z.  Y'all 240Z people have a filler plug

Edited January 17, 2018 by Zed Head

[Zed Head]

and a grease reservoir.  Jealous.

[wheee!]

3 hours ago, Captain Obvious said:

Well that's probably not good. I had suggested they were epoxy, but I should have been a little more specific. They are plastic, but I don't know if they are thermoplastic, or thermoset. Sounds like they are thermoplastic...

So how much goop came out? Just tiny dots like what would fill the holes, or once it turned runny, did a large amount come running out of the holes? Like it was melting out of an internal cavity of some kind?

Pics or it didn't happen. 

Not much came out. What DID drain out quickly burned up in the oven at 450 for 20 minutes. There was a little residue on the rack , but from what I saw, it should only be what was in the small dimples on the rack. I don't think there was an excess from an internal cavity.

[Zed Head]

Did you poke a wire in to the dimples?  Blow some air in and see where it comes out.  Is there a rattle inside now?

Just asking the things that I'd be doing...

[wheee!]

Good questions. I will do more investigation when I get home and take it out of the oven (where I left it to cool down last night).

[Zed Head]

If the burnt plastic smells like burnt hair, it's probably a thermoplastic nylon.