I've taken one apart after having used the Loctite on it. It didn't exactly
fall apart by itself, but then there wasn't any need for high explosives to get
it apart either. Heating it up got it loose. I've also read where acetone will
help release parts that have been put together with Loctite, but have never
tried that. I might try the acetone if I ever have to go back in there. I'm
thinking that probably won't be for another 100,000+ miles or so.
I have used loctite in many applications in my career and in this instance with 290, I obtained the Technical Data Sheet and the Material Safety Data Sheet. It is interesting to note that the product has been tested to Mil-S-46163A and ASTM D5363.
The Data Sheet gives the break loose torque, ISO 10964, pre-torqued to 5N-m is 30 N-m (45lb-in) and (270lb in).
1. Remove with standard hand tools.
2. In rare instances where hand tools do not work, because of excessive engagement length, apply localized heat to nut and bolt ot approximately 250 degrees C. Disassembly whilst hot.
Your will note that they quote Mil spec, ASTM spec and the ISO standards. Manufacture do not quote these specifications and standards without acceptance and audit procedures within industry.
Tails 1990 928S4 Auto
One question is, can this loctited assembly be loosened, repositioned and reclamped in a new position if needed with the torque tube (TT) and transmission still together in the car. From my experience, no.
The heating and subsequent pulling, prying, tugging and hammering is done upon disassembly of the TT from the car since there is no other way to generate enough force on the assembly to release the drive shaft from the clamp.
These actions usually cause the drive shaft to move within the TT. The heating, tugging and banging actions are also transferred to the engine internals, flywheel seal, TT bearings and if the transmission is still connected, the transmission converter bearings and internals.
The heat needed in this instance will not come from a heat gun, but usually an open flame source, not too good under the car to begin with, from possibly a welding torch or maybe butane canister. Since the surrounding materials are metal, it will take a long time to heat soak the clamp. The way some are making it sound, it's as if you can run a candle underneath the clamp and give a tug with one hand and the clamp disengages easily. Not.
One thing that is concerning is the white washing of the distinct negative ramifications from using loctite for this purpose. Even from those that are regarded as gurus on this list.
But hey, Loctite sure is cheap!
If cost is an issue, recommend the circlip, bearing and washers routine over loctite.
Constantine and Dave,
Great comments. It is always good to present both sides of an argument, the pro and cons that allows individuals to make a considered choice of what they wish to do. One thing about RL it is not a dictatorial process.
If I ever need to remove or move the clamp and spline section of the flexplate, well that is another question. The spec for loctite 290 quote heat to 250 degrees C, however the extraction force required to move the actual splines is the nub or the question of which I don't have an answer. The specifications for 290 has a section on "clean up" as follows:
"Cured product can be removed with a combination of soaking in a Loctite solvent and mechanical abrasion such as a wire brush".
Maybe the way to go would be first to soak the clamp section with solvent to soften up the 290 and if heat is required to brake the bond then air blow dry and apply the heat via a LPG torch or oxy-acetylene ensuring all safety and fire procedures are adhered to.
The actual method of applying axial force to the clamp to brake it loose and move it will require a bit of investigation and lateral thinking to ensure that no damage is done to crankshaft and engine internals.
However, if and when this occasions and if I'm still capable of crawling under and working on the car, I sure that I will be able to devise a method of manufacturing a puller/breaker to remove the spline with no depremental affect on the crankshaft and the internal bearings. Hopefully this will not happen as my car has only 97,000 km on the clock and all is working fine with minimum kilometer clocked up each year as most of the time I away in my motor home.
Constantine bring up a good point relating to moving and re-clamping. Maybe when and if the clamp is moved after using 290 and then reposition on the spline to give no preloading to the crankshaft, any residue of 290 on the splines will increase the coefficient of friction between both splines and may preclude the further use of any 290? Who knows as the bonding surface is microscopic as the adhesion is by wicking?
As expounded in previous post on the subject of migrating flexplate clamps, I firmly believe Constantine has developed the best method of clamping, however, it is like the old saying goes "horses for courses", so it is up to the individual which route is taken taking all external factors into account in the decision making process of the individual.
As an aside, I once superintended repairing a slipped crankshaft main journal within the crank web where the pin, with a diameter was 550mm, slipped 9.5mm within the crank. In the repair no hammering was used, only heat, dry ice and hydraulic jacks were used. This repair was done in situ as the horsepower of the engine was a mere 6,800HP. Upon completion the engine worked satisfactory.
Tails 1990 928S4 Auto
Starting from the beginning, here's basically how things went in regards to the clamping of the front of the drive shaft. When I initially loosened the clamp, it moved back along the splines, as it typically does, indicating that there had been some pressure on the flexplate. I checked the crank end play and found it to be well within the specified tolerances. I thoroughly cleaned the clamp and shaft as well as I could with brake cleaner, and blew everything dry with compressed air. I applied the Loctite all around the shaft where the splines entered the clamp, and also into the three slots of the clamp. I tightened a new pinch bolt with blue Loctite on it into the clamp to the 66 ft/lbs that some have said Porsche suggested, then marked the junction of the clamp and shaft so that any future clamp movement along the shaft could be easily seen. The assembly was left for a day or two before the engine was started, to make sure that the Loctite had fully cured. After that, the clamp position was checked when oil changes were done, and it had never moved from where it was when I had initially tightened it with the Loctite applied.
A couple of years after having applied the Loctite, I decided to replace some seals in the transmission, get the transmission lines rebuilt, rebuild the torque tube, and replace the torque converter bearings, mostly as preventative maintenance, and to give me something to do as a winter project for that year. At that time the clamp still had not moved at all along the splines of the shaft. When taking everything apart, the front clamp bolt was removed and a small propane torch was used to heat things up. I have no real idea how hot it had to get to loosen the Loctite, but I don't see any reason to think it was much different than what Tails said was the information he got from Loctite. A mapp gas or other hotter torch probably would have sped things up compared to the torch that I used. It's kind of hard to remember any kind of exact amount of force that was required back then. It seems that it really wasn't that much after things got fully warmed up though.
Once the shaft was out of the clamp, I used a toothbrush sized wire brush to clean the remains of the Loctite from both the splines of the shaft and the clamp. That didn't take much effort at all, and the clamp easily slid back and forth on the shaft after I had removed the residue, basically the same as it does with any other clean and loosened clamp and shaft. After everything was put back together, I applied Loctite again the same way I had done originally. That was around six years ago now, and I've never had a reason to touch any of it again since. When checking for any signs of movement, there still hasn't been any. If I ever do have to take things apart again, I might try using the acetone method of loosening the Loctite first, to see how that works. If it doesn't, I'll use heat again.
I had my 87 up in the air last week to top off the auto trans fluid (slow
leak somewhere up around torque converter). While I was under there, I used the
inspection hole to check my drive shaft spline position at the flex plate. I had
performed the locktite procedure over three years ago with, so far, no movement.
So I was surprised to discover that the white paint I had applied was split, and
there was about 2-3 mm of shaft showing between the two paint lines.
So I removed the cover, loosened the clamp, and the shaft retracted back into the coupling to where the paint crack closed up completely again. I didn't have time to reapply the locktite procedure, so I just tightened it again, and reinstalled the cover. I know I'll need to get back in there again soon to address it. For now, I've left out the two rear cover bolts. I'm gonna install shorter ones so I don't have to drop the exhaust each time.
I had heard that the locktite approach was virtually permanent and would require substantial heat if/when it ever needed to be taken apart. And perhaps I missed it, but I've never heard of anyone ever having the locktite break loose. Clearly it did the job for over three years. I will probably just apply it again, and hope it gets me through another three or four years...
Mark in Atlanta.
87 S4 Grandprixweiss Auto (Daily, Since 2005).
88 S4 Silbermetallic 5 Speed Manual (Weekends).
84 S Schwarz Auto (Daily, 97-05, Sold, Still running around North Atlanta).