Clutch M/C & line - plastic to metal conversion on a '92 4.0?

Anybody ever do this?

Okay - after my second plastic clutch line blowout on the trail in the past five months, it's not just bad luck. (I'll stay away from a rant about "cost-saving" Chryco engineering changes!)

Both times the line failed at the "knee" of the line at the firewall, where it passes near the downpipe. Guess is that they run too close in flex conditions and the line weakens from heat.

Happened at NACFest (naturally this wasn't a parts shop stocked item), so we tried a CG fix that night using an '87 metal M/C and a 50" length of quarter inch metal brakeline w/fittings. Bled OK, but couldn't get any backpressure on the pedal and get it to engage. Maybe the replacement M/C malfunctioned somehow - need to tear it down and look.

Anyway, other than the need for a flexible connection in the line (to allow for body - engine vibration), can anyone think of any other issues regarding swapping in an '87 metal M/C for a '92 plastic one?

We've already allowed for the fact that it bolts up slightly differently to the firewall, and I notice that the pedal travel is different, but we still aren't sure whether or not there are any other mechanical or geometric conditions we're not thinking of. There shouldn't be any issues that the '87 M/C works with a B/A - 10, while the '92 has, of course, an AX-15, should there? This just seems like straightforward hydraulic pump replacement - the clutch or slave itself weren't affected.

Could try and fix this by staying OEM and just using heat tape on the line, but the metal solution just sounds a lot more reliable.

Thanks in advance for any advice.

Well, at least I got to practice my speed shifting on the way home!

Mike in NJ atriot:

Mike, since I was peripherally involved in the attempted repair, I'm very curious to see how it's all going to shake out. Do you want to plan a work
session at your place on Saturday? I can bring tubing cutters and flare tools.

I still think the pedal bottomed out the piston and the rubber cup just didn't return. May have to put a spacer under the clutch pedal to allow for the different stroke, or snag a clutch pedal setup from an 80s vintage wreck.

LOL I remember the first time I met Ron Stevick in person...we were checkin out the underhood of my 89 MJ and he went mad-dog & started tearing all the paper tags off the wire harness, coolant lines etc...I was like "WTF!!!" he explained how his (94) clutch line burst and all that stuff caught fire. Wasn't a couple months later my plastic line failed -no fire :dunno: - and I got a replacement at NAPA and it was rubber/metal. I kept the OEM (plastic 89) MC

I'd agree with Eagle...check out the piston, but it shouldn't be a problem to swap out to a steel MC as long as the bore and stroke/linkage are similar (or compensated for)

Heat tape on the rubber portions isn't a bad idea either...

If ya need a pedal assy or whatever from my 87 MJ, Holler back! We got UPS down in these parts too.

Mike I feel for ya. I lost two of them also, first time nearing a pass above Silverton, had to drive the trail to town then 550 back to Ouray without a clutch...spooky. Anyway, I cut mine near the MC and down near the slave cyl ahead of the 180 deg loop. I found a brass barbed fitting X MIP and stuck it into the plastic line (very tight fit). From the MIP thread I used a FIP X 1/4" compression adapter and ran 1/4" copper tubing, sleeved that with a scrap piece of shop air hose for protection. Worked great.
As a side note, both times it failed during a prolonged pull at about 2000 RPM. I've seen the rear tube of the header glow RED hot while duplicating it parked with the hood up. Looked like a serious lean condition. The motor is out right now for a rebuild, I'll see if it repeats the problem after it's back together. HTH. TC

BTW, mines a '91, searched all the part's stores, all said it was a dealer item. I wasn't going to pay 60 bucks for a piece of plastic tubing again.

TC wrote:

both times it failed during a prolonged pull at about 2000 RPM.

Click to expand...

. . . interesting you should say that. This last time it failed just as I finished towing Doug Farrar back to Paragon's main lot after his crossmember had a major disagreement with Sluice trail. About a mile or two in low range probably closer to 3000 rpm. Put out the clutch to stop at the lot and "thar she blows!!!" Yep, the Borla was probably pretty warm. Then again, the first time though was in 14" of snow at Paragon in December just cruisin' through a bunny trail.

I hear you about the $60 plastic line, that's why CHW's suggestion of the '87 metal M/C and brake line sounded good. A bit more expensive, but, if we can finally get it to work, I won't have to worry about another line breaking (the next time in the Utah desert!)

(Eagle - no need to run down - we're going to take the M/C apart in a couple of days and see what's up inside)

Sorry for everybody else's pain, but strangely it is a little encouraging to hear that this isn't that unusual. I had never heard of this happening to anybody else and just thought I was snake-bit (I chalked up the first break to a 198,000 mile service life! ).

Anyone else with some advice or other tidbits about this conversion - keep it coming! Thanks.

Mike in NJ atriot:

I got some good advice for ya, try not to have 30 people standing around giving 18 different scenarios for how it could or couldn't be fixed Of course, having a clown underneath helping out the guy that's trying to drink brake fluid helps too :yap:

Sean

Yeah, but listening to all of the entertainment arty: above and below was keeping me awake throughout all of the "UP" - "DOWN" commands :lecture: (wait! isn't this a family site? :shocked: ).

Besides, had to keep the :jester: busy, he hadn't broke anything all day and looked bored (but happy) with a :cheers: in his hand.

I figure this was good practice for Slickrock Campground activities in a few months!!! :yelclap:

Mike in NJ atriot:

When I upgraded my tranny to an AX-15 I had a local shop build me a stainless line using pin adapters I got from Advanced Adapters. If you go this route make sure they get the timming correct on the new line so it'll hook up at both ends. I couldn't see that plastic line holding up long running so close to the exhaust pipe. As far as bleeding the clutch slave cylinder that can be a real PITA. I ended up depressing the cup in the slave cylinder with a wooden dowel and holding it in place with a C-clamp then bleeding the clutch hydraulic system. Once the slave cylinder starts building pressure remove the dowel and continue to bleed the system as normal. If removing the dowel lets air back into (losses all pressure) then go in steps; first the dowel then a spacer then try it without any spacers. Good luck - It take some time but usually works.

WA Woody

Man am I glad I checked out this post! I'm gonna check out my plastic line and see if there's an issue there! I don't think I'm gonna try to swap it out for metal line -- too much work! Plus, I paid the stealership's price for a new one when I swapped out my '93 internal slave in favor of a '99 bellhousing with the external slave.

Guess I'll be buying some heat tape!

Thanks Guys!!!

Reading this thread makes me really miss my 5 speed............Mike, let me know when you're ready to talk AW4 swap.
Best mod I've made to my rig.

If you're still working on growning that 3rd foot........ a custom SS line seems like the best way to go, then shield it with heat tape or tube sleeve to keep the high temps away.

XJEEPER

Why not splice in a hard line where the soft line is? You can buy the connectors at any parts store and double flared line too! All you would have ot do is cut and flare the lines to the MC and the Slave! Or am I missing something?

Replacing Plastic Clutch M/C line

The problem is where the line ties into the new style external slave cylinder; they use a pin style connector. This part can be had from Advanced Adapters (AA), or maybe your local hose shop. Where I lived they didn't have a clue on the pin adapter I needed to make up a stainless line so I ordered a couple from AA and had they built the line. Total cost was around $45.00 and a hell of a lot better line than the plastic stock one IMHO. Good luck.

Wa Woody

(in response to Ghost's comments...)

On the '92 4.0 AX-15, the line from the Clutch M/C to the slave is hard plastic. It is attached at the M/C end by a roll pin, and a plastic slip joint at the slave (internal) end.

Don't see how you could splice in a steel line by simply cutting out the center section of plastic line - since I'm not aware of any connectors that would join the two types (the plastic really can't be flared and isn't "soft" enough for any kind of a pressure fitting).

Trouble with just replacing the whole line with 1/4" steel line is at the M/C end - the OEM one is also plastic and is not a threaded connection - that's why we are going to try to use an '87 M/C - it's metal and has a threaded male stub. Some minor issues with firewall mounting and piston arm length, but all surmountable. We don't think there are any other issues with the swap ( ) - as long as there is some flex in the line somewhere.

(There is apparently an Advance Adapters braided S.S. replacement line that has the right kind of insert fitting to work with the plastic M/C, but we already went down the road of replacing the M/C. The A.A. line becomes an option if we can't get our "mod" to work right).

Bottom line is - for those of you stick handlers that weren't aware (like me! ), make sure your plastic clutch line is heat protected (or replaced) along the firewall to avoid any middle-of-nowhere "surprises".

. . . . and, as far as replacing my precious 5 speed with a slushbox . . . . :scared:

Mike n NJ atriot:

Mike,
In some of the high pressure oil lines on the equipment at work(plastic,400+ psi) there is a metal sleeve we insert into the line and use a standard compression fitting and metal furrel (sp).
Some lines are 1/8" up to 5/16" and I know we have 1/4" stuff.All of the fittings are standard NPT threads.
Wayne

Oh, so the whole line is plastic? From the M/C to the Slave? And a plastic M/C? What year did they start that fiasco?

Oh my, this thread brings back bad memories!
I blew one while I was out playing in the snow resulting in a flash fire(and me quickly extinguishing it), had to drive almost 100 miles without a clutch. I ended up fixing it by cutting off the damaged(melted) parts and joining them with a length of hard metal brake line. I sharpend the two ends of the metal line then heated it up red hot and jammed it into the platic line to act as a bridge. I dove on it for a couple of weeks and couldn't find the fittings for a custom line at the time so I got another one from the dealer for about $50. I now carry my old one(the one I fixed) as a trail spare.
I guess I'll be giving AA a call.

Jes