| Author | Message | ||
     Richard Treacy Grand Master Username: richard_treacy Post Number: 974 Registered: 4-2003 |
Just when I thought that it was all solved, my Turbo R steering fluid level started to drop AGAIN, just 15 months after the last exchange replacement. That one is from a 1996 model car, and has the external backlash adjustment screw.. Ho hum. Even though the rack is under warranty, I have decided to overhaul it myself this time to find out what's really going on. I am informed by the repairers in the UK that Turbos suffer far more than the others, and my guess is that it's due to the increased heat from the exhaust cross pipe just near the rack and the turbocharger above the rack. Time to make up an improved heat shield or two. Darn it. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 546 Registered: 9-2004 |
Richard that is rotten luck. Is it leaking in the same place as before. My original SS2 rack is still going strong but await the day when it will no doupt fail. | ||
| David Gore Moderator Username: david_gore Post Number: 555 Registered: 4-2003 |
Hi Richard, Some thoughts "from left field" on this. Would fitting an externally mounted [i.e outside the engine bay] oil cooler on the inlet side of the rack reduce the fluid temperature enough to cool the rack body/seals and avoid the need to install heat shields which no doubt will present some difficulties? I suspect the under-bonnet heat from the turbo engine is heating the P/S fluid to very high temperatures as it is my understanding there is no cooling provided for it. The continuous recirculation of the hot fluid plus the radiated heat from the exhaust pipes are probably generating rack temperatures sufficiently high to soften the seals and allow wear/leakage to eventuate. In my opinion, fitting heat shields on their own may not solve this problem. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 975 Registered: 4-2003 |
Thanks, Pat, fot the sympathy. The leaks are always the same: the primary main seal on the turbocharger side fails. That's why I suspect excessive heat is causing damage. I have checked the subframe and mounts in case they are allowing flex to stress the rack, but with no joy. Speaking to the repairers, I am not alone with this problem almost exclusively chronic to Turbos it seems, although the other cars need rack changes regularly too. The company which does the bulk of the rack overhauls, supplying to almost all UK outlets, shifts a dozen racks each week: that's quite a few considering the relatively small number of cars with these racks. For David: my thoughts exactly on excessive heating, especially in slow city driving. There is of course already fluid cooler, a small unit in front of the radiator. I even had a discussion yesterday with the people in the UK about fitting a larger one and increasing the heat shielding for the rack at the same time. Watch this space. Last time I removed the steering pump and bench tested it to check for overpressue: no problem, and also checked the return hoses for a blockage which could cause overpressure. I am also considering to remove the line filter I fitted in case it is causing back-pressure. Luckily, the leak became suddenly worse not too far from home, and not half way into a 1,000km trip planned on the weekend. The leak went from nothing to undriveable over the last 100km. The sign was internal fluid loss, none on the floor, but I was not surprised when it finally started to overflow from the breather yesterday having had this problem too many times already. | ||
| David Gore Moderator Username: david_gore Post Number: 556 Registered: 4-2003 |
Hi Richard, If the cooler is the same miniscule unit fitted to the Shadows; this is only functional in the Arctic/Antarctic regions given the very small surface area of the heat exchanger core. I was thinking of a conventional A/T oil cooler located in a suitable place where it gets a good flow of ambient temperature air and away from the engine bay radiant heat. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 976 Registered: 4-2003 |
One seal kit, which arrived at my doorstep in Zürich 12 hours after despatch from the UK. Now I have a job to do...  | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 977 Registered: 4-2003 |
David, that's a good suggestion. Come to think of it, why not simply connect the transmission circuit to the steering (same Dexron fluid) and do away with its dedicated reservoir and cooler ? I would need to test the steering and transmission fluid temperatures first, something I shall do as soon as I have done the present job. Many vehicles even share the suspension, brakes and steering circuits in various combinations (Citroen all, Jaguar two etc using LHM). I checked once with Castrol about LHM as an alternative steering fluid, and the result was positive too. What disturbs me is that the leak appeared in cold weather, but then underbonnet may be very hot regardless. Given that the turbocharger is very rarely called upon under normal use, the turbocharger itself is not generating extra heat. Maybe a more effective heatshield is enough to negate the proximity of the exhaust to the rack, a feature not found in naturally-aspirated cars. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 985 Registered: 4-2003 |
After two evening's work, the rack's back in since Wednesday, and so far so good after a test drive to collect my daughter from Kindy. I have to let the air bubble out completely before I can see if the level is stable. It is still slight strawberry milkshake, which is normal for a day or two. The removal took 30 minutes, and installation 2 hours including fluid filling, bleeding and cleaning up. I spent quite some idle time on assembling the rack itself and taking photos, but I was in no hurry. I have some thoughts on the problems these racks suffer, and I feel that the solution will be woundingly simple. 1. The PTFE bearings on my last exchange rack had no gap. The book specifies 0.008" minimum, and actually 0.050" is probably fine. I set the gaps to 0.018" on the new ones. The problem is with too small a gap. The urban myth is the same as with engine piston rings, where too small a gap leads to disaster whilst a very wide gap does no harm at all. As the bearing expands with heat more than the tube does, it wears rapidly on the outside until it is a perfect fit. That means that the outside diameter is OK, but the bearing is loose on the rack bar. The seals cannot cope with any loosness on the solid /non-pinion end, so the seal squashes sideways and leaks very early in its intended life. The pinion end has the floating piston, and is trouble-free. 2. An improved main seal is overdue. Preferably, one with an expander would do, or even a 0.020" oversize outside diameter. You could even place a flat neoprene ring around the bar and under the seal to expand it. Watch this space. Rack in bits  Ready for refitting.  | ||
| bob uk Unregistered guest Posted From: brig-cache-4.server.ntli.net |
The way the rack is mounted to the subframe is the main problem with this rack. As the subframe twists the rack twists as well. Maybe there is something about the Turbo's suspension's settings that causes the subframe (and rack) to twist more. A solution would be to redesign the mountings so that the rack does not twist with the subframe. But maybe the rack is part of the torsional strength of the subframe as an assembly. use synthetic oil. (Message approved by david_gore) |
