Shock oil replacement question(s) 1948 TC

[bergxu]

Hi gents,

Noticed some oil leaking from my left front lever shock and decided it might be a good idea to (for now, they’ll get rebuilt in the future after other more pressing projects get done…) refresh the oil in all of them on the car. I ordered a litre of Motul SAE20 motorcycle fork oil off of Amazon which I believe should be enough to do all four shocks, however I’ve not been able to find any information on changing the oil in the shocks themselves. Right now the car is up on my lift so all wheels are off the ground and will be for the next few days while I wait for the new tires to be installed. So, questions as follows;

1. Does the car need to be on its wheels to obtain a correct fluid level when refilling?

2. I did read that one should fill until just the bottom of the “threads”, now, as I removed one of the presumed fill plugs (centermost 5/16W bolt on the top of the shock) I’m confused as to whether that meant bottom of the threads of the bolt when it’s screwed in or threads of the shock housing as it seems the bolt threads go further down than the threads on the body of the shock. So if I fill to the bottom of the housing threads, there won’t be much room for expansion of the fluid, so what’s the right level or amount to aim for?

3. Can I stick a syringe with a small tube attached through the fill port and extract the existing fluid or do the shocks need to be removed and dumped out through the fill port?

4. Anything I should be aware of when disconnecting shocks if they do in fact, need to be removed? (eg…Will they be under much tension? I seem to recall that when I disconnected the rear lever shocks on my TR6 they had some ‘spring back’ which surprised me as I figured they’d be unloaded if the wheels are off the ground.)

**any other tips/pointers of course are appreciated. I have a nice small fluid pump which I was planning to use to refill the shocks as it has a very small diameter hooked tube that I can put right inside the fill ports and it’ll fit perfectly which, presumably, should negate the need to remove the rears for filling, unless I have to remove them anyways to drain.

Regards,
Aaron

[Duncan M]

Leaking from where? Endcap or where the arm goes in?

[bergxu]

Leaking from the end cap.

[Steve Simmons]

Hi Aaron, you have the correct type of fluid. To answer your questions...

1. No, the shock merely needs to be level, whether on or off the car.

2. The correct fill level is when the end of the bolt (the unthreaded part that extends beyond the bolt threads) is wet. Any higher is unnecessary and will likely result in oil being forced out through the shaft seal.

3. You cannot drain the fluid without turning the shock upside down. The shock body consists of a lower chamber where the pistons are, and a reservoir area above it. The syringe will only be able to remove fluid from the upper area. To drain, you will need to remove the shock, turn it upside-down and work the arm up and down to "pump" the oil out of the pistons. When you re-fill, you will pour oil into the shock and work the arm up and down to get the air out of the piston chambers, then top it up and repeat until there is firm, even resistance throughout the entire travel of the shock arm. You will want to hold the shock in a bench vice or in some other secure way, as the resistance is quite strong.

4. There is no pressure in the shock. It's simply a resistance device. So it can be in any position to install or remove. While they are off would be a good time to replace the two shock link bushings if they are old and worn.

[Duncan M]

Have you tried carefully tightening the end cap? Some people use silicone sealant on the threaded end caps, and if they did that you are out of luck. If they used a non-hardening sealant or thread dressing (like you should) then it may simply be a matter of tightening it up. If they used silicone, then tightening it will not stop the leak, most likely. Never use silicone sealant on threaded parts! Be careful with those end caps and you can re-use them.

[bergxu]

Thanks lads, just the info I needed! And I’ll check the end caps and put some thread sealant on them after the shocks are drained. And I’ll order new link bushes too!

[frenchblatter]

Aaron, look on my rebuild blog to see how to rebuild the shocks, Go to Tech Index and follow it from there,

[bergxu]

Thanks Norman, I’ll certainly have a glance. Would that be found on your website?

[frenchblatter]

Aaron, yes, go to the website then choose MG TC then Tech Index, it's the first line and has the info on the seals you'll need. You'll also ned a 10 ton press (or more).

Or just click this: http://www.lotus7news.co.uk/MG-TC-Tech-index.htm

[bergxu]

Much appreciated!

[frenchblatter]

Aaron, yes, go to the website then choose MG TC then Tech Index, it's the first line and has the info on the seals you'll need. You'll also ned a 10 ton press (or more).

Or just click this: http://www.lotus7news.co.uk/MG-TC-Tech-index.htm