Hello, gents. It's been a while since I've been on here but I've got a pretty bad problem and I'm in the market for all the advice I can get before I decide what to do.

To make a long story short, the threads in the housing where the transmission cooler line meets the transmission are stripped. This is apparently the fault of the last person to bolt the line on; I noticed it was leaking from there and when I tried to tighten the bolt, I loosened it first and now it just spins in place and won't tighten at all. For some reason I did start the car with it in this condition and fluid poured out as if I'd turned on a faucet. I'd say something like a pint came out in the 15-or-so seconds it ran.

I don't know if the cooler line meets up with the tranny in the same place on all the various w123-era M-B transmissions that are out there; on mine it's in the vicinity of the modulator. Unfortunately it's up high enough that a solution like a helicoil would require the transmission to be removed. By the way, the line is held on with a union bolt.

A helicoil would theoretically work, but this involves drilling, I think, and transmisssions don't really like lots of little metal shavings, do they? So this solution gives me pause.

I have purchased some Permatex stuff, similar to J-B Weld, that could rec-create the threads. It says it can hold up to temperatures above 300 F, and to the best of my knowledge tranny fluid gets to something like 180 F (so says the owner's manual). If I did try this, and this is an 'if' at this point, I would also use some sort of sealent on the outside in an effort to minimize the impact should the stuff fail. I do wonder what kind of pressure exists in this line when the car is running, though.

If anyone has experience with an issue similar to this, I'd sure love to hear about it.

And one more thing, before you lambaste me for even considering a glue-type solution, bear in mind that I don't really have the capability to drop the tranny myself and that this could cost me an awful lot of money.

Thanks in advance.

__________________
Ralph

1985 300D Turbo, CA model
248,650 miles and counting...

Was it cross-threaded? Is there any metal stuck in the treads of the fittings?

Were the fittings all the way in the housing, or just partly.

The helicoils may be your best bet. If the threads at least have some "bite" to them, the permatex stuff may work, but know you will have to do it again if you want or need to remove the lines again. You also have to watch for temp and pressure ratings.

Either way you are going to have to drain the tranny fluid, and clean every thing really good.

Which line is it? It would be good to know how the fluid flows and which line it is. If you were to tap it, and this line drains into the pan, then it will not be so bad.

If it goes to the oil pump, then that will be a different matter. Either way, shavings or parts of the dried epoxy stuff can get lodged in the pump.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Good questions. Frankly I don't know the answers to most of them.

The fluid has been drained but I have yet to clean out the threads in the housing, so I don't really know how bad it is yet. I guess that would be step number one before I proceed. I do know there are a small amount of metal shavings in there already - there were a few of them on the bolt when I removed it.

I'm not sure which direction the fluid runs on this line. Guess I need to figure that out.

I'm not too worried about having to remove the line in the future. With luck I won't have to. Without luck, well I guess I would cross that bridge when I come to it. It sounds like the worst case scenario in that event is no worse than the solution would be now if I don't use a glue-type product.

I do wonder about the pressure in this line. I don't know how much there is and that's something I need to find out. I'm guessing it's not tremendous, but a guess isn't good enough.

Thanks, you've given me some important things to think about.

__________________
Ralph

1985 300D Turbo, CA model
248,650 miles and counting...

Whatever you do, I believe you can remove the rear transmission mount and lower it down far enough to improve access.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I'd use a Time-Sert instead of a Helicoil, much better product

__________________
'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

Never heard of a TimeCert. Is there a web site for that?

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Hello. I can see your problem on not being able to drop the transmission. The best way still is to drill it and use a heli-coil or other brand insert. However, let me dig into my bag of "alternative engineering" tricks and maybe this will work. I also realize this is unorthodox and some people will not like it but in an emergency it might just get you mobile. Go to an auto part store or even a Home Depot and get a brass nipple with threads on one side that are close to the size of the hole in the transmission. The threads are a plumbers thread which gets larger the further it is threaded in. See the attaches picture if you need. Wrap the threads with some teflon tape and thread it into the transmission. Go easy as it is making its own threads, you don't want to break it off or damage the hole further. Just go easy and get it in a few threads where you feel it is secure. The next step is cringe inducing too but use a rotary tubing cutter to cut the banjo fitting off of the cooler line cleanly in a straight portion of the line. Save the end you cut off. Now use a piece of rubber hose and some clamps to connect the nipple to the line. Slide it on several inches and use 2 clamps if necessary. Now, as far as reversing this at a later date, you can use a compression fitting to re-attach the banjo fitting or replace the cooler line with a new one. As far as the transmission goes, at a later date the the hole will have to be drilled oversize anyway and tapped to accomodate the new thread insert so whatever the brass nipple does to the hole will be gone. You may have to experiment with different size nipples to get the right one but I know this will at least get you out of a pinch. Good Luck, Eric.

Attached Thumbnails

 

__________________

1984 300D, 246k, veggie, sold
1982 300SD 301k

Before you cut the cooler line, realize that the replacement line costs $50-60 and takes several days from the dealer.

A 1985 300D CA car with a 722.4 tranny uses a smaller banjo bolt than its federal cousin with a 722.3 tranny. The CA car has a 17mm hex head while the federal has a 19mm one. The metal cooler lines are the same except for the banjo. I dont think any adhesive will last. I think your safest option is to tap the hole (whether using a helicoil or using the federal cooling line). I doubt if you can tap without removing the transmission.

__________________
'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

i would try the brass fitting idea.No big deal if you cut the line, as being a cooler line there is not alot of pressure and it can be reconnected with a piece of hose and some clamps if you ever need it again. Once you find a fitting that will start to screw in,stop clean the threads on the fitting and the hole with some spray brake cleaner.Once that is dry coat the threads on the fitting with the slow JB weld and force it in there the best you can if it gets tight to turn quit and let it harden overnight.Connect the line to the barb with a hose and use 2 or 3 clamps where it goes on the tube.If it works great,if not the worst you are out a few bucks and no worse off than you were. Other possibility if a fitting will almost start in the hole but not quite go buy a tap that size and cut some threads and then start the car for an instant to blow out the chips then put your hose fitting in. My $.02 Don

__________________
Red Green "This is only temporary,Unless it works!"

97 E300D 157000 miles
87 300TD ?141k? miles

I did that for about a week while waiting for the correct part after my line cracked without any problems, but it's still a hack. I certainly wouldn't leave it that way any longer than necessary. YMMV

I would explore very carefully the threads on your fitting and hole it threads into.

Is this a banjo fitting? I was picturing a hard line with a flared end. If that is the case a helicoil may not be possible.

Tom W

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Yup, the hard line has a banjo fitting, and the banjo bolt is what threads into the tranny housing.

Another out-of-the box idea for your consideration would be to constuct some sort of "saddle" connection. Some sort of plate or flange that could be used to clamp the line in the existing hole. You may be able to drill and tap several small shallow holes in the area, or use some existing holes (such as the modulator) to anchor the thing.

Rick

__________________
80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

Thanks for the suggestions, guys. I don't have Internet access at home so this is the first I've seen them.

So far I've tried wrapping the bolt in dental floss and using the Permatex thread repair stuff, and neither of those things worked. When dental floss was first suggested I thought it was a crazy idea, but I disocvered it will hold up to boiling water, so what the heck? The threads were apparently too far gone for it to bite, however.

The brass nipple idea is an interesting one and one I haven't thought of; I will think about that. Kerry, I hope the hole can indeed be accessed in the way you suggest. Biodiesel300TD also suggested that.

As it stands right now my car has a date with a mechanic on Monday. He quoted me what I thought was a pretty good price and if he's able to do it without taking the tranny out it will be an even better price. I'll definitely mention the possibility of removing the rear tranny mount only.

In the meantime I'm still thinking over my options, however I'm not going to have a lot of time to play with things as I'm going to be working a lot between now and Monday.

__________________
Ralph

1985 300D Turbo, CA model
248,650 miles and counting...