revilla Posted March 1, 2015 Share Posted March 1, 2015 There is very light surface rust on some of the rear chassis rails around the rear suspension area. It's very light at the moment, but I guess the fact that it is there at all suggests the powder coat is no longer sealing. The picture below shows what is by far the worst area:Background info, the car is a 2003 SV, so it's taken 12 years to get to that state. It hardly ever gets wet because I only take it out when there's a nice big picture of the sun on the weather app on my phone and it's on SORN over the winter so it doesn't even know what salt is (yeah, OK, I like polishing it). However, car is a "keeper" so I'm thinking long term.Question 1)a) Treat it now before it goes any deeper. b) Leave it until the next time the suspension is off for bushes or the like. c) Stop worrying.Question 2)a) New powder coat. b) POR15. c) Hammerite satin black.My inclination right now is probably to wait until I have to take it all apart for some reason and get it powder coated while it's off at some point in the future, but all opinions gratefully welcomed.Thanks,Andrew Link to comment Share on other sites More sharing options...
Pete - W.Sussex Posted March 1, 2015 Share Posted March 1, 2015 I had a bit like that on mine, but perhaps not quite as bad. I rubbed it down to bare metal and used the Hammerite satin black. It's been fine for over a year. Link to comment Share on other sites More sharing options...
DJ. Posted March 1, 2015 Share Posted March 1, 2015 Don't leave it, the sooner it is dealt with The easier it will be to fix. Duncan Link to comment Share on other sites More sharing options...
Grubbster Posted March 1, 2015 Share Posted March 1, 2015 Mines the same age and in bits at the moment so I'm giving it a coat of satin black hammerite while access is good. Por15 is better I believe, but I haven't got any so hammerite it is. Link to comment Share on other sites More sharing options...
Ozzy Posted March 1, 2015 Share Posted March 1, 2015 Bit of a difficult angle to tell, but I'm pretty sure you don't have the later type strengthened De Dion tube, so you might want to keep a close eye on those damper mountings as well.Oz........... Link to comment Share on other sites More sharing options...
SM25T Posted March 1, 2015 Share Posted March 1, 2015 Now he'll start fretting ! Link to comment Share on other sites More sharing options...
revilla Posted March 1, 2015 Author Share Posted March 1, 2015 @SM25T - Yes! Actually I do think I have the "Early SV" type and I'm aware I need to keep a close eye on the welds. It all looks OK at the moment. Link to comment Share on other sites More sharing options...
Mrp Posted March 1, 2015 Share Posted March 1, 2015 Go with Pete W Sussex's advice. I did the same. A good clean rub down and re paint.Mrp Link to comment Share on other sites More sharing options...
SM25T Posted March 1, 2015 Share Posted March 1, 2015 Mine is an October 2002 SV .... Perhaps I need to look at my DD ? Link to comment Share on other sites More sharing options...
TomB Posted March 1, 2015 Share Posted March 1, 2015 Scrap it off and paint it, with a brush of wax oil / dinitrogen over the paint it will last for years. You won't be able to powder coat the chassis unless your very serious! Link to comment Share on other sites More sharing options...
SM25T Posted March 1, 2015 Share Posted March 1, 2015 Dinitrogen eh ..... is this available from the autocorrect shop ? Link to comment Share on other sites More sharing options...
revilla Posted March 1, 2015 Author Share Posted March 1, 2015 @SM25T - Now who's fretting? :) Link to comment Share on other sites More sharing options...
TomB Posted March 1, 2015 Share Posted March 1, 2015 cheeky Link to comment Share on other sites More sharing options...
revilla Posted March 1, 2015 Author Share Posted March 1, 2015 To be honest I've been chasing a rear-end knocking noise for two and half years, ever since I got the car. It's been looked at by Nick Potter, had various things found and treated but still not cured. It's a very loud and nasty sounding knock but nobody has managed to find it with the suspension on the car. I've had numerous threads running on here, we've been down every avenue of investigation and nothing has sorted it out.I was toying with the idea of having the back suspension stripped down and inspected (proper look for witness marks, proper look at the bushes) off the car. I guess it would make sense to clean everything up and paint or powder coat as appropriate while it's off.My problem is I just don't have the time to do it myself. Much as I love working on the car, what with sorting out engine issues and various other bits I haven't stripped it over the winter and with the demands of two little toddler girls, if I start it now I'll lose half the early summer blatting season. There's also the thought that since this one has been so hard to find, having a really experienced pair of eyes on it sounds like a good plan.Has anyone got any idea how much labour is involved in stripping, inspecting and reassembling the rear suspension and how much I'm likely to end up paying to get the whole job done? I was thinking of going back to Nick Potter or maybe even further afield to somebody like James Whiting if I thought they were more likely to be able to find my problem.PS: Just in case it rings a bell with anyone, one more try; the symptoms are a loud knock that sounds (from the driver's seat) like somebody whacks the top right hand shock mount with a hammer, or like a toolbox of spanners jolting, at low speed on bumpy surfaces. Sounds to me like the noise is right behind my right ear or shoulder but passengers report the noise as sounding more central or even on their side from the passenger seat. 30mph with the left hand wheels running over the shallow dips associated with manhole covers or drain covers will do it every time. It's loud enough that passengers tend to look at you with a look of "what the heck was that?". Embarassing to take people on uneven surfaces as it sounds like it's going to come to pieces. Been in other Caterhams and they don't do it so it's not just me worrying about a TADTS. Handbrake cable properly secured, Watts link ends all seem OK as do all other bearings and bushes, replaced shocks and springs complete with bushes, fitted thicker de Dion end caps to space the calipers away from the Watts link arms, Watts link bell-cranks are on the right way around, no FIA roll bar so big bolt head above the tops of the shocks, no witness marks seen anywhere. Tried putting plastic tape on all the likely contact points to look for marks afterwards but nothing shown up. With both shocks off you can swing the de Dion tube through its full rage of travel and angles and nothing foul or catches. No sign of de Dion fouling differential or bolts or the chassis at extremes of travel. No amount of shoving or bouncing the car reproduces it in the garage. Does seem to be worse with just me in the car, slightly better with passenger. Car has been flat floored and no reason to think the dampers are topping or bottoming out - but just for good measure I tried winding the platforms both and down by huge margins and it makes no difference at all. Still does it with nothing in the boot. No change for better or worse in two and a half years, always there. Even tried driving around with a cheap video camera strapped underneath to see if I can see anything happening, but nothing obvious even when you can hear the knock. Link to comment Share on other sites More sharing options...
SM25T Posted March 1, 2015 Share Posted March 1, 2015 Rod end bearings on the Watts linkage. Amazing amount of noise when they wear. I have a good source if needed. Link to comment Share on other sites More sharing options...
revilla Posted March 1, 2015 Author Share Posted March 1, 2015 @SM25T - Ian I remember you did suggest these in one of my earlier threads on the subject. I haven't tried replacing them but I did disconnect the Watts link bellcranks from the de Dion so I could pull them around and check for play and they all seemed absolutely sound. Would rod ends worn enough to knock be easy enough to spot or is it just a case of replacing them to see what happens? If you really think that it's still a likely cause even when I couldn't feel any play I may try replacing them. How much would a full set cost me from your source? Cheers Andrew Link to comment Share on other sites More sharing options...
SM25T Posted March 1, 2015 Share Posted March 1, 2015 If they turn freely, they are worn. New ones are hard to turn ... off the car. I'll get a price and let you know. Link to comment Share on other sites More sharing options...
sjmmarsh Posted March 1, 2015 Share Posted March 1, 2015 Revillai had a 2001 SV that used to knock loudly when the rear ARB hit the diff (I think) in the middle of the car - I zip tied some pipe lagging round it an that stopped the noise.The other noise I have encountered (on the CSR) was a loud clang (like someone banging two metal plates together) that turned out to be the top of the damper breaking off as it had seized to the top bolt.Nick Potter is familiar with both of the cars.Steve Link to comment Share on other sites More sharing options...
revilla Posted March 1, 2015 Author Share Posted March 1, 2015 @SM25T - I just whipped off a couple and they are still stiff to turn. You can just move them with your fingers but they certainly don't move loosely. @sjmmarsh - Thanks for the suggestions. Unfortunately I don't have a rear ARB and I've swapped the rear dampers to no avail. At least Nick will have seen plenty of examples to give him a few ideas. Link to comment Share on other sites More sharing options...
Dorset7 Posted March 1, 2015 Share Posted March 1, 2015 Do the 3 stage POR-15 treatment - I've just done all my rear chassis while the DD tube was out, looks brand new and will last much longer than Hammerite. Link to comment Share on other sites More sharing options...
sjmmarsh Posted March 1, 2015 Share Posted March 1, 2015 RevillaHave a good look at the chassis tubes as well - it could be that one of the brazed joints has cracked, particularly those near the diff mounts. Steve Link to comment Share on other sites More sharing options...
Nigel Riches Posted March 2, 2015 Share Posted March 2, 2015 Rust never sleeps. Nigel. Link to comment Share on other sites More sharing options...
SM25T Posted March 2, 2015 Share Posted March 2, 2015 Aha ... a Neil Young fan. Link to comment Share on other sites More sharing options...
simonpa Posted March 2, 2015 Share Posted March 2, 2015 Andrew, you can get knocking when the bolts through the Watts-link rose joints (or the olives themselves) wear.I had a car that had been built with standard bolts instead of shouldered ones, there was a mm or so movement on each olive, as teh threads on the bolts had collapsed. You could see the wheel move backwards and forwards when pushing it. It was noticeably noisy, but not a massive clonk. I've had big clonks before and always managed to find them - shame you are nowhere near Fleet!Cheers - SimonPS - I have a set of new rose-joint ends in the spares box, if you decide to change them. Link to comment Share on other sites More sharing options...
Nigel Riches Posted March 3, 2015 Share Posted March 3, 2015 Neil Young, After the Goldrush, Harvest, happy daze. Nigel. Link to comment Share on other sites More sharing options...
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