Rear suspension oil leak

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Topic originally created by JBishop on February 20, 2006 2:14 PM and viewed 2966 times in the old forum.

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Originally posted by JBishop on February 20, 2006 2:14 PM
I have a slight oil leak from the rear left shock absorber ie the most aft shocker on the original self leveling system. The suspension seems to work fine but I would like to put in some oil. How is that done?? Thanks John ps we are having a pre '72 V12 outing with about 45 cars this weekend. I will post some photos next week. I understand we will have 5 of the rare C4s and over a dozen of those more common Daytonas.

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Originally posted by JeffLit on February 21, 2006 2:00 AM
Welcome to hell. Those monsters were originally filled with oil and "gassified" by Koni using a special tool. They are not servicable by mere mortals. You'll notice a small socket cap screw on the side of the body. Koni had a special tool that wrapped around the body of the shock, pressurized via that hole, and allowed the cap screw to be inserted and torqued down without losing pressure. Don't try to open that because the contents are under pressure (not sure of the exact amount but my testing indicates in the 200 psi range). When I attempted the rebuild of mine I added a high pressure schrader valve from some modern Penskes in order to allow the shocks to be presurized with nitrogen when I was done assembling them. I filled them with shock oil and bled them manually via exercising the shaft before tightening down the top. Then I used a hydraulic press and a scale-gauge to measure the effective "spring rate" and added nitrogen via the schrader valve until I got it equal to the rate of the spring on the front half of the control arm. The end result was mixed. They worked great for a while but one day I went to the garage and the car was low in back. I was so disgusted by then I never even checked the pressure to see if the pressure leaked or there was some bypass of oil internally. Pulled them off, went to the coilover spring/shock package from T. Rutlands and never looked back. Lots of pictures at jefflit.net/cars/365gtc4/shocks/ .

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Originally posted by JBishop on February 21, 2006 7:43 AM
Thanks Jeff for that cheery optimistic assessment. I will leave it all alone until I have a performance problem with the suspension. The leak is only minor so I might have a few years yet before all the oil drains out. I will give the car a real test this weekend as we will probably do 500 miles on various roads including some twisty mountain roads. Thanks John

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Originally posted by JBishop on April 24, 2006 1:11 PM
Well I just came back from a drive on the weekend and my rear shocks are GONE. I bottomed out all the time, even over very small bumps. So I am in the process of replacing the rear shocks. I will take notice of all your comments and experiences and go the replacement route rather than trying to fix the original system. 1. When I jacked up the car, the rear shocks were still under tension. The forward spring/shockers came out no problem. Just the rear ones are still under tension, so I have to compress them somehow to get them out. Any tricks in getting the rear shocks out? 2. Jeff. Do you or anyone else have photos of the "coilover spring/shock package from T. Rutlands" or other types of replacements? On Jeff's web site I could only see the repaired originals that Jeff said only lasted a few months, before he gave up and put in the replacements. 3. In another thread it was mentioned "Pep Boys supplied Monroe load leveler shocks". Does anyone have the part number for these Monroe shocks? Also do people just put a shock adsorber on the rear to replace the original Koni damper or do some people put a spring/shocker combination and thus have 2 x spring/shockers on each side? Thanks John

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Originally posted by dbone on April 24, 2006 4:04 PM
John The coil overs appear to be the best solution. I put a set on my car, not from T. rutlands, but from another source in NY. These are from Koni, built as a replacement. As an alternative, before i found the coil overs, and after some long research, I replaced the forward spring with a 308 spring and used a second set of rear Koni's, without the spring, as replacement to the leveller. It was just cosmetic, i believe, to fill in the space of the leveller. The 308 springs are beefier and hold up the rear of the car sufficently. I'll get you a part number and the resouce information, if t.Rutlands can't help. Dave

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Originally posted by Michael Bayer on April 25, 2006 6:03 PM
John: If you look down the Forum a few posts to "REAR SHOCKS AGAIN" there is more on this topic, Michael Bayer

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Originally posted by JBishop on April 26, 2006 9:54 AM
Mike I have definitely decided to go the coil/shock option. My main problem now is how to remove the old self leveler. It is still under tension, and because it is just a smooth cylinder, I can't get a spring compressor onto it. So I need advise from guys who have removed these things. How do you compress them whilst thay are attached to the car? Because they are shot means they don't have too much tension on them but much more than my puny arms can compress them! I need some mechanical advantage. I have the suspension fully extended but the levellers still have some residual tension. Thanks John PS any part number for the Monroe option would be appreciated.

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Originally posted by Aaron on April 26, 2006 2:19 PM
Removing the rear shocks – the spring over in the front and the leveler in the rear. Both shocks are travel limited on extension – neither will come apart. The front spring-over is shorter than the rear so I have always removed it first. - with rear of the car in the air and the wheels off, remove the nuts on both ends of the spring-over shock - put a jack and appropriate block of wood under the rear hub and slowly apply lifting pressure to “off load” the spring-over tension. When the correct upward pressure is applied the upper bolt in the spring over shock should turn some-what freely. Grab the bolt with channel locks and pull the bolt out. If it doesn’t slide out with a good pull then, the lifting pressure is either to great (the spring in the spring-over shock is being compressed) or to little (the leveler is still applying tension to the spring-over shock.) - with the upper bolt removed, let the pressure off the jack and allow the suspension to extend such that it hangs on the leveler. (Note the spring-over shock probably does not clear the upper mounting bracket and can not yet be easily removed.) - Repeat the process with the leveler – remove both nuts - Again apply just slight upward pressure with the jack until the weight of the suspension is off-loaded from the leveler – the upper bolt will again turn much more easily when the tension is off the leveler. – Remove the bolt. - At this point, both top mounting bolts are removed. Slowly lower the jack and catch the shock & leveler as they fall clear of the upper mounts, slide the bottoms off the mounting shafts. - Repeat in opposite order to install. note – 2 items 1. at no time did I use a hammer, punch, press or any other gadget that applies significant force. I believe that as long as the chassis mountings have not been buggered by an idiot, or corroded badly, it will come apart as described. 2. It is possible that the rubber bushings apply upward pressure on the suspension and that instead of applying a slight lifting pressure to remove the upper leveler bolt, pushing down on the hub just a bit with your hand might do the trick. Other item – old socks are great for covering up the greasy splines That is my “2 bits” Have fun Aaron

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Originally posted by Michael Bayer on April 26, 2006 8:22 PM
One other "caution" - when I rebuilt my front shocks (the car had 13,000 miles) I found the bushings in the shocks came from the factory one size too large, so double check the clearances of the bushings and the bolts once the shocks are out and off tension. Michael Bayer

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Originally posted by JBishop on April 28, 2006 6:02 PM
Aaron Thanks for taking the time to give such detailed instructions. I now have the shocks and levelers out. It turned out that the sway-bar (anti-roll bar) was holding the splines up so I could not get enough extension on the suspension to completely unload the springs and levelers. I am in the process of pulling the levelers apart just to see how they work. For future reference the top resevoir had about 1psi in it, the bottom one had about 60psi and the middle one ( the one just above the bottom one) had about 40psi with the shaft fully extended. These are just guesses. I would expect them to have maybe up to 200psi when working correctly. I still have not taken off the bottom cap as I have the thread soaking in WD40 overnight. I will be interested how it is all supposed to work. Thanks again everyone. John

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Originally posted by Michael Bayer on April 29, 2006 9:19 PM
John: There are also extensive (and grim) threads on FChat about the reliability of rebuilds of these unts, be sure to read them if you are considering that option. Keep us informed on how this goes, we will all be in your shoes sometime..................Michael Bayer

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Originally posted by Mike Meehan on April 30, 2006 10:10 PM
Hi John ,sounds like you are moving right along. Will be doing this soon as I have the new units in my garage now.Let us know how you set the tension on the coil . The insert included with the Konis I have said nothing. Kendall Merritt indicated ti as a bit of trial and error. Keep us posted and thanks.Mike

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Originally posted by JBishop on May 5, 2006 2:13 PM
Well I have the "beasts" apart and they look OK except that all the O-Rings are bloated. To my simple mind it looks simple to just replace all the seals and put it all back together!! Sounds simple!! 1. I will replace them though because (to me) having different sets of effective spring rates forward and aft of the rear axle just puts a unnecessary torque on the inboard fixing points. I will replace the levelers with new Koni sets from the 1974 365GT4 2+2 which are still carried by Koni and repair the original shock/coil-overs and set them up to be the same as the new set. Thus having the same effective damping and spring rates forward and aft of the rear axle. 2. I have found a guy who can gas the levelers using the original grub screws, so no welding valves etc. I have included photos of my levelers apart and Jeffs photo. I note that they are very similar but DIFFERENT. The arrows of Jeff's photo points to parts that are not in mine. Also the arrows on my photo points to a part that looks separate in Jeff's photo but is welded to the internal tube in mine. My car was one of the very last made and maybe Koni had made some modifications to fix some design faults?? Once I get it all back together I will give you guys some details on how it all went. John

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Originally posted by JBishop on June 11, 2006 12:56 PM
I have installed the levelers and driven the car a few times over various roads and the car seems fine. The car rides at 25.5 inches to the underside of the rear wheel arches. I will just list a few things I found. 1. The units are easy to pull apart, once you know how. I can now do it in 15 minutes per unit. An O Ring removal tool is useful, as the large top O Rings are in very tight. 2. Once the 2 top O Rings are removed, use a 3mm wooden rod poked up through the top access hole to help push out the centre parts of the unit. The centre parts are stuck in very tightly even after the large top O Rings are removed. Be careful doing this as the internal bladder is held at the circumference. So make sure you direct the rod towards the centre not towards the circumference, and do not force it. You can also use metal hooks into the recirculating holes at the open end and try to pull up the centre section to get it out. 3. The bottom section which includes the main piston must also be disassembled as it has 2 internal O Rings and a very small oil filter. Be VERY careful with this piston as the hard chrome plating can be scratched and then the unit will not seal when pressurised. 4. Overall these units have 6 O Rings each. 2 large ones, 1 obvious one on the outside of the main piston and 3 internal ones that are hard to detect. 1 is on the grub screw inside the main piston, 1 is up inside the main piston bulb which seals the small tube that slides up inside the main piston and 1 is up inside the main tube with the welded bottom plate. Make sure you replace all 6. 5. Make sure you clean the small filter that is inside the small nylon cap at the end of the internal tube which is inside the main piston. It is accessed via the end grub screw which itself is accessed after removing the bottom mounting bracket which screws into the main piston. Make sure you label the piston and bracket pair together as they are a set and may not match the other pair. (The split pin access hole may not line up with a non matched part.) 6. I was able to machine up the seals and bump stops with NO modification to any existing part. I used 22mm diameter wiper seals on the 21.75mm diameter main piston. There is about 2mm overlap so this works fine. These are just the seals which clean the main piston as it works up and down. I can supply 6 seals (2x wipers, 2x main pressure seals and 2x bump stops) for US$100 if anyone is interested. These just fit into the existing units. 7. I pumped mine to 385psi. This might be a little high but I used the numbers listed for the 365GT 2+2 on a Tom Yang message thread. Aaron suggested 350 to 400 psi. I would suggest that 350psi might be better. Anyway 385psi works. To get them pumped, go to a certified Koni shop who will have the machine to pump up the shocks via the cap screws. I was told that a lot of Koni race shocks use this mechanism to pump up the shocks, so a good Koni shop will have this equipment. Once done you can then put them on the Koni shock dyno to make sure they work correctly. The following is a plot of mine. The plot shows the force required to depress the units and then the force exerted by the units on the rebound. Hence it is an elliptical plot. The lower arc is the depression and the upper curve in on the rebound. 8. Overall I found the units to be easy to repair as they only have seals, O Rings and a filter to replace. There are no hardware fittings to machine, replace or repair. If you have any questions please do not hesitate to ask, especially now while it is all fresh in my memory. Please note I suspect that there are some variations from car to car with these things. The photos Jeff shows of the internals of his levellers are not EXACTLY the same as mine. I suspect Koni tried some modifications as time went on. IMPORTANT: I have a 17 page KONI manual in pdf format on these levelers. It is a generic manual that describes the theory of the design and has drawings of them. Note that it is generic and NOT SPECIFIC to those fitted to the C4. However it is helpful in understanding how they work and the drawings give a good idea as to what to expect when you pull them apart. Please let me know if you would like me to email a copy of it to you. Cheers John PS if anyone is really desparate I am offering to fix these levelers for others for a small fee of course !!