W108 Mercedes 280SE diesel conversion project

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pryantcc
Posts: 289
Joined: Wed Jan 05, 2011 6:35 pm

W108 Mercedes 280SE diesel conversion project

#1 Post by pryantcc » Wed Nov 13, 2013 4:32 pm

Hello!
Legislation in Ireland means that any car older than 1980 is exempt from the NCT or National Car Test.
Road tax is at a fixed rate of 56 Euro per year for vehicles more than 30 years old.

I have been hatching a plan for quite some time to take advantage of both of these exemptions. I currently drive a 2.0L diesel Mercedes 190. It costs me more than 700Euro per year in road tax, so you can see my motivation! Yesterday, I purchased a 280SE with a 3.5L V8 engine first registered in 1971. My plan is to replace the engine with a 2.5L normally aspirated diesel and the auto box with a manual one. I drive just over 300 miles a week and, once I find an engine & gearbox, I hope to do it in the 280SE!

Currently there is quite a long list of to-dos, but very few which are essential to forward motion:
Rust bubbles on almost every panel (seems to have been painted relatively recently with poor prep.
Indicator stalk doesn't stay in position when switched on.
Some lights/indicators not working.
No heater or blower.
engine and gearbox swap
Front windscreeen delaminating quite badly
very bad wind noise, I think due to poor window and door seals.
Sunroof which tilts but doesn't slide.
Non functioning and partially functioning electric windows.
Lots of missing wooden trim from the interior.

It drives beautifully, I love it already from that respect. It was quite dull getting into my 190 this morning having driven the new one home yesterday. I will, of course keep you up to date on progress!
Image[/URL]

rich.
Posts: 6804
Joined: Wed Jan 05, 2011 9:18 pm

Re: W108 Mercedes 280SE diesel conversion project

#2 Post by rich. » Wed Nov 13, 2013 5:32 pm

would it be cheaper & less hassle for an lpg conversion??
nice car by the way, can we have more pics?

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TerryG
Posts: 6750
Joined: Wed Jan 05, 2011 1:54 pm
Location: East Midlands

Re: W108 Mercedes 280SE diesel conversion project

#3 Post by TerryG » Wed Nov 13, 2013 6:55 pm

Could be interesting but it will drive completely differently with a manual diesel to an auto v8. Have you had a go in a w115 / w123 diesel to get an idea of how a merc diesel performs and what sort of economy you can expect? I can understand why you want to do it but a car like that you should drive because you love it. I doubt even with a diesel it will get more than the mid 20s mpg wise (more on a run, less in town). A modern car will get 2-3x that so you won't be making a saving with the mileage you do (but it will definitely be more stylish than a clio diesel).
Understeer: when you hit the wall with the front of the car.
Oversteer: when you hit the wall with the back of the car.
Horsepower: how fast you hit the wall.
Torque: how far you take the wall with you.

alabbasi
Posts: 244
Joined: Wed Jan 12, 2011 9:54 pm

Re: W108 Mercedes 280SE diesel conversion project

#4 Post by alabbasi » Wed Nov 13, 2013 7:22 pm

It's been done quite often, but most people will go for the OM617 3.0 5 cylinder diesel as it uses a mechanical injection pump and is therefore self contained (no computers etc). With a turbo, it's a pretty peppy engine. The OM602 and OM603 are more modern, but also harder to plumb in.

Shame, the 3.5 is a heck of a motor. If it was me, I'd keep the 280SE 3.5 for the weekend and find a W115 220D or 240D to knock around in.

pryantcc
Posts: 289
Joined: Wed Jan 05, 2011 6:35 pm

Re: W108 Mercedes 280SE diesel conversion project

#5 Post by pryantcc » Wed Nov 13, 2013 8:36 pm

Thanks guys. Unfortunately Rich, LPG isn't as cheap here anymore. The tax on it has been hiked up to try an pay the Germans back for the money they lent us to make sure our bankers weren't out of pocket!!
Terry, I fully expect there to be almost no power at all, but I'm prepard to accept that in exchange for a modicum of economy! I'll be about 300KG heavier than the car it comes out of which is really just 4 adults.
Al, I've been researching engines quite heavily. The 3.0 litres are attractive, but I'm tending towards the 2.5 for that slight economy improvement. Unfortunately, I don't have space for 2 great Mercs, nor very much time for weekend driving (2 young kids). My idea was to get to drive a really nice car which I could maintain myself, and wouldn't break the bank in fuel bills. Fuel here is abut €1.50 per litre, so a big factor.
I also really like the 3.5 and I seem to have got a great one, running beautifully. I'll keep the original engine and 'box in case I ever have to sell the car, it would be an awful shame to split them up.
I'll get some more photos at the weekend when I can see the car in daylight!

pryantcc
Posts: 289
Joined: Wed Jan 05, 2011 6:35 pm

Re: W108 Mercedes 280SE diesel conversion project

#6 Post by pryantcc » Thu Dec 19, 2013 11:26 pm

Sorry for the lack of progress reports folks. The car hasn't been out of the garage since! I found play in the king pins and one thing led to another, and now the entire front suspension has been stripped. There are lots of bits which haven't been greased and need replacing.
I found a leaking injector and sent that off to be fixed. Still not found a donor for the diesel engine, but not in any real rush as it looks like I'll be completely stripping the car to paint it. So, I can bide my time and hopefully find a decent engine and box in a rotten car so that it doesn't cost too much.

I also stripped one door down and found that the bottom 3 inches of the door card had disintegrated. I'm going to make new ones as some insensitive previous owner cut a big hole in the originals and attached obscene speakers to them. The electric window mechanism was attached to the motor with only 1 of the three bolts it should have had. This had caused the mounting plate to bend quite badly, and the motor gear to loose alignment with the curvy thing it runs on. It is very interesting to me that there doesn't seem to be any connector on the cable to the window motor to allow it to be removed!

I will take some pictures at some point and get them up here for all to see, I promise!

alabbasi
Posts: 244
Joined: Wed Jan 12, 2011 9:54 pm

Re: W108 Mercedes 280SE diesel conversion project

#7 Post by alabbasi » Sat Dec 21, 2013 5:18 am

Those window regulators bend routinely and can be expensive to replace. They're the same as those in a W114/W115 if you need to find used. There are lots o grease fittings on these cars, you should really grease them every time you do an oil change (3000 miles) and they'll last for ever. King pins can be bought new but may need a machine shop to make them fit right.

Rear axles can wear due to lack of grease, making an almighty howl when going in reverse.

pryantcc
Posts: 289
Joined: Wed Jan 05, 2011 6:35 pm

Re: W108 Mercedes 280SE diesel conversion project

#8 Post by pryantcc » Mon Dec 23, 2013 10:35 am

alabbasi wrote:Those window regulators bend routinely and can be expensive to replace. They're the same as those in a W114/W115 if you need to find used. There are lots o grease fittings on these cars, you should really grease them every time you do an oil change (3000 miles) and they'll last for ever. King pins can be bought new but may need a machine shop to make them fit right.

Rear axles can wear due to lack of grease, making an almighty howl when going in reverse.
Thanks for the tips!
I have great intentions of forming a regular greasing habit and recording it somewhere too so that I don't end up missing something.

pryantcc
Posts: 289
Joined: Wed Jan 05, 2011 6:35 pm

Re: W108 Mercedes 280SE diesel conversion project

#9 Post by pryantcc » Wed Jan 01, 2014 12:09 am

Slight change of plan! Fate has intervened and placed a 3 litre, straight 6 Mercedes OM606 engine with automatic box into my hands. It's in a 1999 300E. Electronics and software will be a challenge and a steep learning curve, but I have the whole car, so should be able to make it all work. It's pretty common to replace the injector pump on these with a mechanical one from the earlier cars, but I'm going to give it a go with the electronic one for starters anyhow.

Currently, the front suspension on the project car is completely dismantled pending refurbishment. So, the plan now is to get that all sorted out so that the 280 SE is back on 4 wheels and can be moved out of the garage to allow the 300E in for dismantling! Only once I have the donor engine and box working post strip-down will I remove it from the 300 and start on the physical transfer. It will take months as I'm pretty limited for time, but I'll get there in the end...

pryantcc
Posts: 289
Joined: Wed Jan 05, 2011 6:35 pm

Re: W108 Mercedes 280SE diesel conversion project

#10 Post by pryantcc » Wed Jan 01, 2014 8:35 pm

Finally some photos for you all!
You can see the front suspension is just about absent in the pic below. The passenger door is not closed, the alignment is actually pretty good! The paint is pretty fresh, but bubbling through from underneath, so will need doing again.
Image

Here's a close-up trying to show the bubbling above and below the trim strip. This is the worst patch for size, but I have issues on almost every panel. Around the rear screen is the worst I can see externally.
Image

This is the inside of the passenger door. In their wisdom, someone blocked up the factory drain holes with filler and drilled new ones which weren't at the lowest point of the door!
Image

The whole underside was sprayed with Schutz prior to sale. I've scraped off a couple of the rusty patches here, no surprises, I could see they were there before I bought it. It's mostly just surface rust which I'll blast off and re-paint.
Image

The front screen has moisture damage also, so I'm a bit afraid of what I might find in terms of metal when I remove the windscreen rubbers!
Image

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