Original Strut Rebuild

[RestoZ]

Hi Guys

Making progress on the resto and lovin' it. 

Doing a number of things, but the main item at the moment is sandblasting, stripping and preparing the suspension components for respraying. 

 

In the process, I've removed the original strut inserts thinking I would simply replace them with KYB's or some other brand of insert that was appropriate. Being the curious type thought I would pull the originals apart and see if perhaps they might be salvageable. While the oil was shot and there was some build up of crud in the internals, it seems the majority of the components (of which there aren't many) aren't in bad shape at all. 

I've had a look through the threads on suspension, but can't see anything specifically relating to this type of rebuild. 

The main issue I found was the crud had blocked the holes on the piston/main valve at the bottom of the shaft and that would have prevented the flow of oil from one part of the unit to the other. Simple enough to clean out once disassembled. And, I think, the reason why the shocks felt stuffed. 

There are 3 seals in the unit - one on the piston/valve, one which sits under the main insert retainer and one inside the retainer itself

The only one I am worried about is the one on the piston/valve (see above on the right) which seems to be made of nylon or something like it. The other two rubber seals seem fine but I can't tell if this one is sealing or not. 

So, a couple of questions:

Has anyone done this repair previously?

Can you buy a kit of seals and if so where can you get it?

Is it worth mucking around or should I just go buy new inserts?

Is there any info available on volumes of oil etc?

In this build I am trying to keep as much original as possible, so if that means a bit of mucking around and getting things working again, that is the way I would prefer to go rather than the buy and replace approach. 

Thanks 

Paul

 

 

[gilltech]

Back many years ago I just flushed out / changed the oil in my 260Z front struts as they weren't leaking and I was perfectly happy with the damping. If they should eventually leak then maybe I'd just replace the top collars assuming they were still available otherwise inserts would have to be the go.

I can't recall where I found the specs for the oil and quantity, factory workshop manual presumably.

The rears weren't as good so I installed heavy duty hydraulic Monroe inserts in those. [Was $$$ driven choice, fancy adjustable Konis weren't an option].

I don't know if new stock internal seals and parts are available, best scour the 'net to see. I have seen NOS collars for sale on eBay at times.

Early 260Zs had the 51mm dia. struts much the same as the 240Z, whereas later had 56mm dia. IIRC from previous posts you have a 260? What dia. are your struts?

 

[RestoZ]

I have the bigger 56mm ones. There was a thread on here which did mention volumes, but it was a very early thread and I doubt the volumes related to these later struts. 

Have looked on the net, but can't see anything referring to a internal strut rebuild kit. Only had a quick look, so will look again tonight.

I did find this, but not sure if it relates to the later shocks - I don't think so, but will see if I can access a later manual. 

[RestoZ]

Oops, here is the post

https://www.classiczcars.com/forums/topic/39665-240z-factory-cartridge-type-shock-absorber/

[gilltech]

Interesting, I didn't know that Nissan also provided drop-in cartridges as replacements. So maybe that answers your question as to whether rebuild kits are available, as in I guess not! Except maybe the gland nuts, to use the correct term, (not 'collars').

My FSM dated April 1976 page FA-11 specifies 340cc oil for the front strut. Given the date I presume that is for the 260Zs with 56mm struts. (Mine has 51mm).

That same FSM's page RA-8 for rear suspension servicing just says 'refer Section FA'.

As I recall from way back then I couldn't overfill my front struts, when compressed or expanded (whichever it was) they would only take so much.

But, I also presume that there was a different FSM for the late 260Zs which had the taller rear struts, again (presumably) therefore requiring more oil! What year is yours?

Hope that is of some help. But best do your own research.

 

 

 

[RestoZ]

Yea, wasn't sure of the terminology for each of the components, so just made it up as I went along.

Mine is the later 1977 model with the taller rear struts so the manual referring back to 340cc in FA wouldn't apply to my rears. 

But 340 is a good start for the front. I could possibly do some sort of calculation based on the length of the inner and outer components of the rear and calculate the volume based on that. 

Alternatively, if anyone has a FSM which specifies the volumes for each and could provide that for me, that would be most appreciated. Also if the manual provides a weight for the oil, that would be most helpful. 

If I can get these to work, I'll do a write up on the process and post it up here. If not, I'll just buy some drop in cartridges. 

Thanks in anticipation.  

Paul

[gilltech]

Quote

if the manual provides a weight for the oil, that would be most helpful.

My FSM doesn't call up the weight of the oil, just says (quote) 'Use genuine shock absorber oil "NISSAN GENUINE STRUT OIL" or equivalent'.

IIRC, way back then I used ATF oil. Which I think is about 10W, or maybe 5W/10??? Same as I used to use in my dirt bike motorcycle forks. Maybe there's something more specific available these days.

I think try and get hold of new gland nuts if still available.

Edited February 6, 2021 by gilltech

[RestoZ]

OK, an update on this post. 

I wanted to go through the process of seeing if I could resurrect these struts, so after disassembling, cleaning and reassembling I managed to buy some 10W motorcycle fork oil which effectively is the same as the oil specified in the FSM. 

Filled the front and back housings with 340cc of oil as specified in the later FSM I was able to download and following the procedure outlined managed to get the air out and get good controlled suction and discharge but was not able to maintain pressure. The piston rods slowly dropped to the bottom after about 5 minutes of being pulled up. I suspect the seals on the piston had worn with the crud that was allowed to accumulate in the strut and just the general use over the years. 

So, given I haven't been able to find replacement seals or a kit, looks like KYB's will be the go. 

I'm sure most people would go down the replacement cartridge route, but I needed to check this as an option. Hope this saves someone a bit of time in the future. 

 

[CBR Jeff]

Paul

What you described is normal. The only thing holding the strut shaft (standard original units) at full travel normally is the spring. The weight of the shaft will eventually drive it down through the oil as there is no opposing force to keep it suspended in the oil. Most cartridge units and modern shock absorbers have a gas charge in them that acts on the outer ( in the case of a twin tube system) compartment forcing the shaft up. The gas pressure acts as an air spring.
You may be able to get replacement seals from a hydraulic supply company. 
 

Jeff

[gilltech]

Ditto what Jeff says.

Having done all the good work you've done I think all you'd need now, preferably, thinking long term, are new gland nuts as they contain the external seals and keep all the dirt and crud out. But I don't know if the 56mm gland nuts are available, I've only seen the 51mm ones on Aus eBay. Maybe NOS ex the USA?

FWIW later 260Zs than mine had rubber gaiters to keep the dirt out, like on motorbikes.

[RestoZ]

OK, mine do have the rubber gaiters and they are still in good condition, so I can place them back on when the time comes. 

The interesting thing though is Jeff's comment "The weight of the shaft will eventually drive it down through the oil as there is no opposing force to keep it suspended in the oil." My limited knowledge re these shockies presumed that if they dropped, they were stuffed, but thinking about it now if I was getting controlled suction and discharge then presumably the piston seals were doing their thing. Whether it is to the required/desired degree is hard to know until they go back in the car, but I'm starting to think it might be worth taking the chance. At about $500 for replacement cartridges, it's certainly tempting.

I will take the piston seal to a hydraulics company and see if they have anything similar. 

I haven't seen 56mm gland nuts advertised either, but mine look in good condition and didn't leak when I was expelling the air from the strut and that entailed turning it upside down when discharging. The manual says to add some grease on the inner of the gland nut seal when reassembling and presumably that helps with the sealing process. 

Thanks for the feedback guys, most helpful and will make me pursue this further. I'll write the process up if it all works, but it could be a while before the old girl is off the rotisserie and back on her own four wheels. 

[gilltech]

Well if your car still has the rubber gaiters and in good condition then the  gland nut seals will surely have been well protected.

I only suggested new ones as all the rubber gaiters I've seen on 260Zs have been dry rotted.

Good effort on your part to preserve existing parts rather than just discard.