Common R129 problems

[Sid The Kid]

I am starting a thread to try and get feedback on some common R129 problems.
These are somethings I have noticed that are common problems on the R129 from what I have seen. I have a 1991 500SL.
1) on the rear tailights condensation builds up inside
2) on quick de-accelartion the transmission will thunk
3) the compartments on the arm-rest door area seem to break.

[tecqboy]

I don't have problems 1 or 2. And fixing problem 3 wasn't too hard. But one unusual thing I've discovered on several older 129's is that the doors rust out along the bottom edge. You'll never see the problem unless you open the door, get down on the ground and look up at the seam behind the rubber weather strip. Since this takes a bit of effort, the problem goes un-noticed. So, if you own a 129 or are considering buying a used one, check it out.

[Gilly]

On the 500's, there was a real problem with the original distributor caps. There may still be some out there too, there is no service interval on them. You need to get Bosch caps and rotors on the early ones or you can have problems especial in hot weather (especially if you're going to use it in a parade, as often happens to convertibles).

Lots and lots of soft top sealing problems, there are several tech bulletins concerning updating the seals. First two or three years of production were really messed up in the seal area.

I also believe there are problems with AC Evaporators on 129's, you don't hear about it as much as the 140's.

Steering leaks: MAJOR thing to watch for is a seeping steering gear box. Big buck repairs. The steering gear box alone for a 129 or 140 with SPS is a few thousand bucks, for a reman unit, assuming one is available. There are also repairs/updates that can be done to fix leaking power steering reservoirs.

I don't recall seeing a problem with condensation in a 129 taillight though?????

I see this mainly is intended to look for problems in the 500SL's. I would further warn the folks who are afraid of big repair bills to think twice about buying a V12. They are great to drive, but they can consume huge amounts of green when something goes sour on it.

Gilly

[LeaUK]

Just to add my personal 2pc and in no particular order:

1. Electric window motor - badly squeaked and was much slower than other side.

2. Central locking IR receivers (receiver in door type) - drivers door fails during daylight hours, but fine in evening. Also complete intermittent failure of IR system (possibly linked but yet to be proven).

3. ASR - intermittent ASR light due to split accelerator bowden cable sheath.

4. Hunting/surging when below 10deg C - Watch out for elder models with no CAT as they cannot adapt to air leaks (which are inevitable with a +10year car). These minor leaks will not be automatically corrected bhe engine managment system due to missing O2 sensors (ie no CAT). Runs perfect above 10deg C!

5. Distributor caps and rotors (as mentioned by Gilly) - replace immediately, possible risk of complete breakdown otherwise.


Apart from these minor annoyances these are truly awesome cars.

Tecboy
I get the odd 'cluck' from the transmission too and so I'm about to change the fluid and filter/seal. What was your cure?


Lea

[Gilly]

Oh, and there is a bulletin concerning the breakage of the brake booster line on the 119's also, the first year or two. They'd break off on the engine side, near where they go under the plastic engine trim. Seen this a few times, the engine won't run with that big of a vac leak.

Gilly

[Vinalf]

Lets include all the 129 series.

1) I have heard that the 300SL has had head gasket problems

2) The 600 has ignition harness problems (due to excess heat)

[KenSilver]

When I corner hard, my seat belt indicator comes on as I roll over in the seat. (I know that's a lightweight observation, but I tend to leave all my mechanical problems to my shop and fix them with the folding green )

Ken Silver
--------------
~1993 SL500, glistening triple black, xenons: http://www.kensilver.com/SL
~1999 SLK 230 Kompressor, silver /black, CD, immaculate (my wife's)
~1991 Daimler, shiny grey / grey leather, best in country!
~ex 350SL, 230E, 280E, MX5 and a lot of other makes not nearly as nice.

[Sid The Kid]

Oh and another annoying thing I have noticed is the headlight wipers always seem to get stuck away from their start position. I see so many SL's parked with one headlight wiper half way up the lense and the other on the bottom of the lense where it should be.
tecqboy - how did you fix your compartments when they broke?

[LeaUK]

My headlight wipers only get 'stuck' if I turn the head lights off before they have completed their cycle. Now having said that there is the very odd occasion that I can't explain! Ho hum!!

[billwrb]

Hi! consider yourselves lucky re: the headlight wipers....I don't even know how to make mine work ... or whether they automatically work in conjunction with some other function!

[KenSilver]

Take the headlight wipers off. They're butt-ugly anyway, and I've also experienced the weird non-return park position - could never figure it out.

And what if the spray was not working (common), and the wipers scoured and ground their way over the glass!

I've been driving for the best part of 40 years and never experienced the need for the headlight glass to be superclean. I certainly don't know why anyone would drive their SL on a dirty country road at night anyway... I always plan my trips to be on tarmac!

Ken Silver
--------------
~1993 SL500, glistening triple black, xenons: http://www.kensilver.com/SL
~1999 SLK 230 Kompressor, silver /black, CD, immaculate (my wife's)
~1991 Daimler, shiny grey / grey leather, best in country!
~ex 350SL, 230E, 280E, MX5 and a lot of other makes not nearly as nice.

[tecqboy]

Answering 2 questions here. My transmission does not clunk on a down shift. I have a 1991 300 SL and they use a 5 speed automatic, so it's a different transmission than all you guys with 500 SL's have.

Ah, those loose door panel pocket and hinge covers. The problem is that the plastic "studs" which secure the panel to the door frame crack / break and seperate from the frame structure at the back side ( inside ) of the door. The factory originally holds them on with a "speed" clip. I dis-assembled my door panels and drilled out the studs from behind. That is, I drilled a hole about 1/8 diameter into the stud about 1 inch deep. I then screwed self taping sheet metal srcews ( with a large washer ) into the studs to re-attach the hinge subpanel. It's difficult to explain, especially without a picture, but it's not difficult to do. And once you have it apart, you'll see the problem. The hard part, of course, is removal of the door panel from the door. I wrote up a "how to" on removing the panel and I'll append that next.

To remove door panel 1991 300SL.


1. Carefully remove the door lock knob by pulling outward ( parallel ) to release.
2. Using extreme care, remove the wood trim behind the door release handle by lifting outward with a panel removal tool.
3. Extract the single screw securing the metal trim behind the door release handle.
4. Remove the single 10mm bolt securing the door latch assembly to the door.
5. Carefully remove the seat control assembly and wood trim on the door panel using a panel removal tool and prying outward on the outside edge.
6. Remove 1 screw from inside the door pocket on the outside edge of the door in the pocket hinge assembly.
7. Remove the single very small screw from inside the pocket on the inside edge of the pocket securing a piece of plastic molding. Remove the molding and extract 1 large screw securing the door pull handle and panel to the door.
8. Extract 1 screw securing the black trim piece around the door latch. Lift up from the bottom to remove.
9. Extract 3 small screws securing the chrome trim on the top of the outside edge of the door panel and remove trim.
10. Remove the courtesy lamp assembly at the bottom of the door panel by snapping it out with a panel removal tool.
11. Using a panel removal tool, carefully release the “pop” fasteners from around the perimeter of the door panel. Lift up on the door panel to release the metal clips from the top edge of the door panel.
12. Slide off the vacuum hoses from the connectors near the panel bottom.
13. You are now holding the free door panel.

Reverse steps for installation.

[Sid The Kid]

wow thanx a lot tecqboy.

[ldcleve]

I believe in looking in the other posts on this ASR topic and my own cars switch failure at 14K miles, that the moisture entering into the neutral switch and causing the ASR to engage is another common problem on 129s.

[EuroRash]

Has anyone had problems with responsiveness of acceleration?

I used to own a 92 500SL (sold to a neighbor but now he's offering to trade for a 97 E320 I just purchased).

Symptoms are, inconsistently from a stop, quick acceleration onto the freeway it will not get full power.
Could it be the fuel pump or dialing in the fuel dissy and or throttle body?
It seems to run and idle fine otherwise.
Could be adjusting the transmission linkage due to I installed a new one from Sun Valley Mercedes before selling it too him.
Though I doubt it since it's inconsistent.






I'd like to do the trade but the W210 runs so well with only 90k miles. Everything works even the original IR remote (17" TSW rims and new tires).
I like the R129 because of the larger rims, H&R sport springs (handles like a go-cart now) and the removable top of course. Has IR lock issues, the soft top is shot and doesn't work (hard top does lock/unlock), and the paint and body is a bit rougher than the W210. Though it only has 100k and the transmission is new.