My '86 GTI build

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walterclark
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Re: My '86 GTI build

Post by walterclark »

My day on Sunday at Okemo 1 was cut short when I came down from the first run and found blackish brake fluid dripping from the boot of the clutch master cylinder onto the interior floor. The MC still seemed to function but not knowing what happened, I decided to drive the car onto the trailer rather than have a problem on the hill that might strand the car...It does not play nicely without a working clutch release.

I didnt get to do anything about it until yesterday due to NEFR. But I did order another Wilwood clutch master cylinder last week. This model does not have a rebuild kit available, but at under $50 a pop its isnt too steep. Too bad though because a kit with this seal could probably restore it to like-new.

Yesterday I pulled the MC and opened it up. From what I could see it looks like the rubber seal on the front edge of the piston must have been compromised. There was a little shred of black rubber in the boot along with a fair amount of blackened brake fluid. The only seal in the MC that is black is this one. It looked OK visually and I could not see where that shred of rubber was torn from but it must have come from it. It appears that if the piston is pushed too far into the cylinder this seal would run into a natural color rubber O-ring that is seated at the front of the 3/4" bore and if the rubber seal were pushed further it would have to either fold back into the piston or somehow compress and ride thru the O-ring. So I am guessing it was over extended or over pressurized - maybe the slave stopped moving when its rod maxed out the bearing release arm movement. I did some measurements and determined that if I were to push the clutch pedal to the floor, the way the whole thing was set up, I could exceed the 1.4" rated stroke of the MC. There was generally no need to push the pedal anywhere near that far in as the clutch action all occurred near the top of the pedal stroke, but it must have happened.

This is the master cylinder disassembled.

Image

Thi is the piston assembly. The seal that is likely the problem is the black tapered one on the right next to the piston on the far right.

Image

When disassembling the system I was careful to not suck whatever contamination was in the MC and feed line any further into the slave cylinder and I cleaned and purged the line and slave with fresh brake fluid before reassembly. There didnt appear to be any significant contamination in the slave and its not leaking so it seems to not have been harmed.

So, in went the new MC. This time I have added a rubber bumper to the floor behind the pedal to stop it short of that 1.4" stroke.
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britracer89
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Re: My '86 GTI build

Post by britracer89 »

What you have there is an exact duplicate of Girling clutch master for Triumph TR6 as well as other various British makes and models. It's British.......it's supposed to leak. That's also known as lubrication. So what if it only lubricates your feet on the pedals.

I've also been told that if you stop the leaks then there is a chemical or pressure related issue that lets all the smoke out of the wires. :? ;)

See ya at Okemo, Brian "British Tin Can Driver" Dennis
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walterclark
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Re: My '86 GTI build

Post by walterclark »

britracer89 wrote:What you have there is an exact duplicate of Girling clutch master for Triumph TR6 as well as other various British makes and models. It's British.......it's supposed to leak. That's also known as lubrication. So what if it only lubricates your feet on the pedals.

I've also been told that if you stop the leaks then there is a chemical or pressure related issue that lets all the smoke out of the wires. :? ;)

See ya at Okemo, Brian "British Tin Can Driver" Dennis
:lol: :lol:
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DaveEstey
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Re: My '86 GTI build

Post by DaveEstey »

I run the same clutch master so now I'm looking to minimize the pedal stroke to avoid this.
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walterclark
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Re: My '86 GTI build

Post by walterclark »

I finally took a look at my videos from Okemo 1 turn 8 (check 3) where I always lift the right front powering out of the turn. In none of them did I see any jump in RPM indicating inside wheel spin. While my practice times on Saturday and warmup run Sunday were well off my best time (from 2013), the speeds thru turn 8 were very close to that 2013 best time (40mph at the apex) and as is usual I went WOT at the apex which in the past has always results in wheel spin until I back the throttle down a bit or the car straightens and sets down. So this Wavetrac diff IS doing what it claims.
Last edited by walterclark on Sun Jul 26, 2015 7:38 am, edited 1 time in total.
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Rabbit Farmer
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Re: My '86 GTI build

Post by Rabbit Farmer »

So this Wavetrac diff IS doing what it claims.
Good news! Okemo 2 will be my test for the WaveTrac in the Golf.
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walterclark
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Re: My '86 GTI build

Post by walterclark »

After running Ascutney and Okemo twice and at each event not getting anywhere close to my times from 2013 or 2014, I decided to stop blaming the driver and look at the data.

In every case I am slower by some seconds and terminal MPH at the end of all the "straights" and seem to be carrying at least the same speed thru corners.

The only thing that has changed in all this is the transmission. Sure, the brakes were changed too but as I got comfortable with the new feel I was back to braking at similar levels to when I had the vacuum power boosted version.

When I switched to this transmission (an AYK 02A that originated, along the the 2 liter 16 valve engine I am running, in a 1990 Passat) I knew there would be differences because of the taller gearing. I hoped it would mean I could go faster, but I was wrong.

The 020 transmissions I ran before were geared with 4K ring and pinions with a 3.94 ratio. The 02A I have uses a 3.68. The ratios of 1st thru 4th among all the 02x 5 speed close ratio trannies is nearly identical, so it is mainly the ring and pinion that sets them apart. I know that a lot of guys covet the 4.25 R&P that could be found in 020 diesel transmissions but those were fairly rare and long since been gobbled up by astute 1st and 2nd gen VW racers so I had settled on the 3.94 from the 4K which is pretty popular with road racers.

After a little research I determined that the 4.24 ring and pinion that is in the 02J EGT (and a number of other variants), that is the standard transmission on nearly every Mk4 Golf and Jetta, was originally a part from one of the 02A variants (CRU) found in the Corrado. In the official VW parts lists it even carries the 02A part numbers from the 02A.

With a Lot of luck I was talking with John Hart at Ascutney last weekend and he indicated that he had removed an 02J and replaced it in a customer car because of a problem that prevented it from going into 1st gear but otherwise, it was a low mileage 2003 transmission and was available if I could use it. John checked on Monday and the variant was indeed an EGT. On Wednesday I arranged to drive up and get it from him. Thursday I took it apart. Exactly what I wanted. I also cleaned the 02J inside and out and bagged it up in case I need/want to use it someday. Why not just swap it in place of my 02A? Couple reasons. First I would need to move the new limited slip diff over so both transmissions would have to be torn down anyway. Second I needed to fix that 1st gear problem. I was able to determine what it was and with a dremel tool de-burred the hub teeth preventing the shifter form selecting 1st, but I think the right fix is a new 1-2 hub. Third and biggest is the lightened flywheel, custom clutch and pressure plate I bought for the 02A is larger than what is called out for the 02J. It might actually fit in the bell housing and the input shaft spline is the same but there is no way to bolt a starter motor to that combo. I paid a good chunk of cash for that flywheel/clutch/pressure plate and dont want to do it again. I learned that there seems to be no market demand/value in a good used lightened flywheel/clutch/pressure plate (the set from my 020 is still for sale) so I dont want to replace it again.

So here are a couple pics:

After pressure washing the 02J:
Image

The ring gear and output shaft stack (pinion) removed:
Image

And here they are cleaned up:
Image

The last image makes the parts look brown for some reason. Not sure why as they are not like that to my eye. Maybe it is some sort of auto tint in the Samsung S5 as the background is way more bright-blue that that. Also, I dont like the look of the bearing either side of the pinion. Some dulling, scoring and heating is visible on the outer races, so they are going to be replaced before going into the 02A. I plan to do that sometime after Philo.
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walterclark
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Re: My '86 GTI build

Post by walterclark »

The drive train is out, transmission removed, on the bench and drained waiting on me to take it apart again to swap in the new ring and pinion.

One of the updates I want to do over the winter is to find a way to compensate for the removal of the vacuum brake booster. The new pedal set has the same ratio as the OEM and the master cylinders are slightly smaller than OEM (.75" Wilwood versus .86" OEM), which should have made the pedal travel a little longer for a given amount of fluid moved and say a .875" MC, and thus require less effort to achieve a given amount of pressure. However, I feel the effort is still too high and this year I didnt feel was able to decelerate as rapidly as in previous years. Pedal travel is probably about right to where it firms up though so I dont think I have a size mismatch where I cant modulate the brakes or have to move the pedal too much.

I seem to have 2 directions I could go. Find pads with more friction than the ones I have been using, or go with bigger front brakes including multi-pot calipers and larger front rotors.

The bigger brakes approach has a lot of appeal since they could not only increase the stopping power but because multi-pot race calipers have no dust boots and retract on both side, they have a little less drag when not being applied. Besides they look cooler. But...I dont have overheating problems with the present brakes so I dont need larger rotors for any reason other than increased friction leverage.

The pad swap all around would be quicker and way cheaper.

I have identified and priced the bits I would need for the big brake upgrade and the price isnt terrible...around $1200 including similar pads to what I would go with for the pads only approach for both the front and rear. One of the issues with the larger brakes is that, as measured, I would only have about 3mm of space between the caliper and the wheel rim (not the spokes of the wheel, the ID of the rim itself). That is the minimum any of the race caliper makers recommend and that would not allow for easy passage of any but the smallest stones. Since our roads do have places where the pavement is broken up and there is always that gravel mile at Mt Washington, this clearance might be too little to be a prudent choice.

The pads I am presently using are Hawk HT-10 on the front and Mintex Redbox on the rear. I have used the HT-10 for years now and with the vacuum booster I was able to compensate for the need to get them hot before the friction levels came up by added pedal pressure. The RedBox on the rear are street performance pads with a different CF versus temp profile (more bite when cold) and that may have been something of a contributor to the 2 high speed spins (Mt Washington and Ascutney) I had since 2011 since both were preceded by a tap of the brakes.

I checked around and while Hawk makes several compounds that should be better (similar or better ultimate CF but much higher at low temps), they dont make them to fit my car. I looked and a few other notable brands but found similar problems...nothing for the brakes I am using. Then I remembered that a rally friend that also ran an A2 Golf for years swore by a brand called Carbotech. I looked into them and found they offer a wide range of compounds including a few that seemed like they would do well, and they make them for my brakes. I contacted them by email explaining what I have, the issues I want to address and for recommendations. They were very quick with a response and specific suggestion including different compounds for the front and rear to match my setup. The pads arent cheap (around $350 for all 4 corners) but if they do what I want, they end up being almost $800 less than the brake upgrade plus pads above. Since I also need a new helmet and harnesses for next year, having that extra savings will be handy.

I still want to ponder this a while before I pull the trigger. Thoughts?
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sciroccohp
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Re: My '86 GTI build

Post by sciroccohp »

always had good luck with Porterfield pads, I don't like the idea of bigger brakes, the stock brakes with the pads I got I can lock them up anytime with 255 A6's. don't want the extra mass or slower acceleration (nevermind the huge inventory of 13" wheels I have) I have to find out which compound I have been using.
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walterclark
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Re: My '86 GTI build

Post by walterclark »

sciroccohp wrote:always had good luck with Porterfield pads, I don't like the idea of bigger brakes, the stock brakes with the pads I got I can lock them up anytime with 255 A6's. don't want the extra mass or slower acceleration (nevermind the huge inventory of 13" wheels I have) I have to find out which compound I have been using.
Are you still using the vacuum brake booster?
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