Mercedes SL320 R129 - Part 2

Mercedes SL320 R129 - Part 2



Original Poster:

100 posts

45 months

Friday 1st November 2019
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r129sl - Your car is cutting power at 144!!!! Jings, that sounds fast. For two reasons that will not happen to me.
I have the economy model so it won't get to 144 and I am quite a sedate driver. I enjoy a bit of brisk driving but I am usually pretty close to the speed limit and as I am only driving in the UK, that means 70 ....ish.

Your warning lights issue does sound odd. I would love to know what causes that and what the solution would be.

Deefor62 - Thanks for the info on the N10. The cover on mine appears to be held on with 6 allen bolts and it looks like I would need to remove some of the scuttle plastics to get to it. The only problem at the moment is the heated rear window not working so I will leave it for now.

I have not decided if I will fit the hard top over winter. The car is garaged but will come out for some of the nicer days where the soft top will probably be down anyway.

So, to the update -
I ordered the TPS and the strut tops from Mercedes. Just as I was arriving at the dealership there was a late model black R129 leaving. It's always nice to see another one out and about.

The parts man was summoned from the basement where they are kept for the odd occasion a punter wants to buy parts.

The first strut top was a bit of a struggle but the second was a doddle. Easy when you know how.
When I changed the front lower arms earlier this year I was left with a grating noise when turning. Quite irritating.
There is a very small gap between the ball joint and the brake disc on my car and I had been unable to get it just right.
So, while I had the wheels off I made a more concerted effort and with a bit of careful twisting managed to sort it.

The TPS was an easy changeover.

Well, what an improvement!
I can't put my finger on it but I think the combination of the new strut tops, sorting the grating when turning and the smoother throttle action have combined to make the car feel much better.

I have had several good runs in it with the temp gauge down at 6.5c with the roof down. It does get a bit cold when travelling quickly.

Still no sign of the BAS/ESP light and I haven't noticed the gauges dropping since the day it went to the Indy specialist.
Cured! (ok, that might be a bit optimistic)
I'm not looking for problems so I will leave that problem alone.
If it comes back I might look into aftermarket replacement ABS rings for the rear.

I had a good look at the the old and new strut tops. They have a production date stamp in the mould and looking at them I am fairly confident that my new ones which were made in 2017 came from the same mould as my original 1999 ones and that were used all the way from 1989. This is based on the positions of the stamps which are slightly irregular and match.

Picture taken near the nuclear sub base.

I ordered new tyres from Oponeo and was surprised to find that they were shipped via DPD all the way from Belgium.
The wheels are booked in for a refurb on Wednesday. They didn't really need done, but there are some minor corrosion and scuff marks and two of them lose pressure so I am hoping that refurb and new tyres will sort all that.
And, I like shiny wheels!

It's probably an age thing, but I do not get the current fashion for black alloys.

Having been surprised by the difference the new strut tops made, I have also decided to replace the rear shock absorbers. Apart from being a bit corroded they seem fine but as they are nearly 20 years old, have done 115k miles and all the other rear arms and bushes are new......
The new ones are in the post from Germany.

When I was coming to the end of the rear subframe overhaul I noticed that a bit of the underseal on the seam behind the offside rear wheel, under the battery was a bit crunchy when I pushed it.
At that point I did not want to investigate further as I had already packed the welder and paint stuff away.
An optimist might think that it will only be surface rust but past experience leads me to expect it to be worse than it looks.
While the wheels are off I will sort it out.


27 posts

20 months

Friday 1st November 2019
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Only just spotted this thread, it's brilliant, I have a 2000 SL edition and think these cars are seriously under-rated.
Even the last are now nearly 20 years old but they are so well built.
Please keep going with the updates


Original Poster:

100 posts

45 months

Monday 18th November 2019
quotequote all
So, carrying on from my last update -
Time to get these fitted

A fairly straight forward job apart from the awkward access to the top nuts.
The spanner needs to go through the 3" hole that is just below the fuel filler pipe. It is doable but I could only get 1/12 of a turn at a time on the spanner so some patience was required.
I have occasionally considered buying ratchet ring spanners for just such situations but it seems a bit extravagant for the few times I actually would use them.

And job done

Next it was onto the crusty section below the battery, just behind the rear wheel.
This is what it looked like on initial inspection.

I scraped away the underseal and loose rust with a screwdriver and it seemed quite solid. For a moment I thought I might get away with some wire brushing and rust treatment.

However it did not look so good after a going over with the wire brush in the angle grinder.

So I removed the battery and the battery tray. Strangely, the two bolts and two nuts that hold in the tray were all loose. Odd.
The rust was very localised.

I cut out a rectangle with the grinder and shaped a plate to fit. Proceeded with my usual attempt at welding, got more scars on my arm from spatter while welding upside down.
Not pretty, but plenty strong enough.
I treated it with Hydrate 80 and painted it with Electrox zinc paint followed by a coating of Dynax UB on the underside.

This is it with the Electrox applied.

While it was jacked up I took the opportunity to get the wheels refurbished and the new tyres fitted.
The finish on the wheels is good but there are a few inclusions in the paint that are a bit annoying.
I fitted a new set of centre caps which were £9 off ebay. They are ok, but you get what you pay for.
I will give the originals and clean up and may refit them.

The sum total of all the changes made have resulted in the car feeling more composed on the road, particularly at speed.

Just coming up to my first year of ownership so it was time for the MoT which it passed. The guys there were quite complimentary of the condition which was nice to hear.

I have used the same local garage for Mot's for about 30 years although I think it has had about four owners over that time.

I've done about 3,200 miles in the year and my spreadsheet shows a little over £3,000 spent on it, nearly all of which is just parts with the only purchased labour being 2 hours at the local Indy and the wheel refurb.


2,946 posts

186 months

Tuesday 19th November 2019
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Wonderful. Now, if you could just do the outstanding bodywork and then let me know when you are selling... wink

I've managed a total of 500 miles in the 124 in the same space of time. Not great.


2,411 posts

179 months

Tuesday 19th November 2019
quotequote all
Good work, you are saving that car. Most owners would be oblivious.

Noob question but when you reconnect the battery you have to re-sync both windows and turn steering wheel lock to lock, right? Anything else that needs calibrating too? I may lift out my battery and inspect underneath. Cheers


Original Poster:

100 posts

45 months

Tuesday 19th November 2019
quotequote all
Hi J
500 miles isn’t much but time passes and there’s lots to do, especially with a young family.
I haven’t decided what I’ll do about the paintwork and bodywork yet. Maybe next year.
As it is, I’m not too precious about using it.

When I opened the doors for the first time after reconnecting the battery the windows drop to half height. It’s just a case of winding them back to the top and holding the switch for a few seconds to let the car know where the top position is.
When I started it the bas/esp and abs lights were on. I drove to the bottom of the drive, turned the steering full left and right and drove off. The light immediately went off.
I don’t know if it was the steering or the speed that reset the lights but all good.
BMW bikes are like that every time it’s started. The brake warning lights flash until you get to about 3mph.

The only other issue was needing the radio code.

However, I would not have been able to see or feel that rust from below the battery as it was mostly under the forward facing edge of the wheel well panel and was under the seam sealer.
Probably easier to find from below, just behind the plastic wheel arch liner.

Edited by Yogioes on Tuesday 19th November 17:49