HELP.

I live in Irealnd and petrol or gas is $.90 a liter or $4 a gal.

I drive 30K per year. I am just about to lose my company car and I can buy a lovely sec 500 (1987 with 101,000 miles and a full MBSH)

However at 16 mpg I simply could not afford hte gas.

I really want this car but will only buy it if I can transplant a merc diesel endine into it.

Do you know if any engines mentioned below fit in reasonable well?

Really appreciate any advice.

Model Years Chassis # Engine #
300D Turbo 87 124.133 603.960
300TD Turbo 87 124.193 603.960
300SDL 86-87 126.125 603.961
350SD 91 126.134 603.970
350SDL 90-91 126.135 603.970

It should be possible to drop any one of those engines in your SEC but it'll probably cost you more than 2 years' worth of gasoline. Not to mention the potential loss in value of the car itself. But maybe a Diesel SEC/SDC will be worth a fortune in Ireland.

If your SEC has self levelling suspension and you want to keep it then your only choice is the TD as it will have the hydraulic pump. But maybe 603 hydraulic pumps can be transferred between wagon and sedan heads.

Sixto
91 300SE
87 300SDL
83 300SD

sixto

really appreciate the reply.

sixto

Do you know if the diesel will mate with the standard auto transmission and is it likely thet the exhaust downpipe and engine mounts will need to be fabricated.

Any other obvious headaches I should look out for?

Any ideas how I would find out more or any ideas who could give me more info.

All favours will be recorded are rewarded in Guinness if you are ever over Ireland direction.

Thanks in advance.

Here are things to consider:

- A 500SEC has two exhaust pipes from the engine bay to the rear muffler. A 603 has one big pipe to the rear muffler. No complex bends or anything. You can probably shorten what you get from the donor car.

- There are some electronics to transfer from the donor car since the 603 has the Electronic Diesel System (EDS). Much simpler if you don't have/keep EGR and AIR because you won't need the airflow meter. There's also the glow system, of course.

- MB Diesels of this vintage have a vacuum switch at the starter key (since it's not an ignition key) that shuts off the engine when you turn the key to off. You'll have to get this switch from the donor car or build an electrical version of a vacuum switch.

- You'll need a glow light in the cabin to tell you when the engine is ready to be started. It would be nice for this to be part of the main gauge cluster but you can fit the light anywhere.

- The fuel tank will have to be drained and cleaned. I've heard of folks filling their Diesel tanks with a a gallon or two of gasoline with no ill effect so I don't think the fuel tank will have to be removed and chemically cleaned for the conversion.

- On the other hand I don't know if the fuel level sensor and mesh filter in a gasoline tank will work with Diesel fuel.

- You'll also have to figure out a way to bypass the electric fuel pumps, filter and accumulator since the Diesel injection pump has it's own fuel pump and filters.

- I expect the fuel return line will hook up.

- I expect Ireland doesn't require a restrictor plate in the fuel filler that won't allow a Diesel nozzle to fit.

- The air cleaner on a turbo engine sits on the fender so you'll have to fabricate a mount for that.

- I don't know why you couldn't keep the SEC transmission. At most you'll have to replace the transmission vacuum modulator.

- I don't know if engine mounts will have to be fabricated. I suspect it will be easier to modify the crossmember to accept the new engine mounts.

- If the Diesel was not mated to an automatic it might not have the vacuum controller on the injection pump that the transmission will need to shift properly, nor will you have the vacuum amplifier and cold shift compensator switch. The latter parts can be added. I don't know if a vacuum controller can be added to the injection pump if not originally equipped.

- I think the radiator necks are in the same location in all 126 cars.

I'm sure this is just the beginning of the things you'll have to consider.

Sixto
91 300SE
87 300SDL
83 300SD

Bob Sowle in Avon, Indiana, USA installed an MB 2.4 L diesel with its tranmission in his 450SL. The sub frames are the same. The switch required some minor surgery and he installed flexible lines for the oil filter. He fitted a turbocharger with no wastegate and commented that the faster he'd drive it the faster it would go. He claims to have gotten 100 mph out of it.

I think a diesel from a w126 chassis car would be your best bet. if you can find an entire diesel w126 car as a donor, you should be able to swap everything needed I would think.

It sounds like it would be an interesting conversion. I'd love to see a diesel SEC. considering the w126 came with a diesel engine option, I would think if you found an entire car, you could pretty much swap whatever you needed for a pretty straight forward swap, but you may have to gut the car first.

Alon

__________________
'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon

Same is true about every car I've driven

Sixto
91 300SE
87 300SDL
83 300SD

I did a little more research on the 126 line:

The radiators are different between US Diesel and gas cars. I don't know if that means you can't just find hoses to fit.

US Diesel cars have an engine oil cooler while US gas cars don't

The US SDL has the clutch fan in a slightly different location than the V8s so you'll need to work on the shroud.

The motor mounts are the same between the V8s and SDL so that shouldn't be an issue if you can find SDL brackets.

I don't know how in love you are with your transmission. As Alon says, your best bet is to find an 87 300SDL as you have the best chance of parts matching right up. Particularly the transmission. The potential problem of keeping your transmission is that you likely have second gear start on a gas MB of that vintage. The SDL probably isn't suited to second gear starts. You can modify your transmission for first gear starts but there's another expense.

The other thing I might have already mentioned (too lazy to check) is that if you need a 603 motor with a leveling pump, you might be stuck with a motor out of a wagon unless sedans also came with leveling suspension in Ireland.

Consider trading your SEC for an SDL and welding the rear doors shut

Sixto
91 300SE
87 300SDL
83 300SD

sixto, Ashman, Robby Ackerman really appreciate your time.

If I do go ahead with the transplant I will keep you updated. Promise.

Now Welding the back doors shut on an SDL does sound tempting LOL

Why not convert the petrol engine to dual fuel using LPG? I don't know the duty position in Ireland, but in the UK the saving is considerable. A guy I know converted his BMW 750i to LPG and gets the money equivalent of 40mpg.

__________________
Cheers, Neil

LPG v's Diesel

LPG = €.70 liter

Diesel = €.90 liter

Petrol = €1.0

Assume the MPG from LPG is 25% less than petrol

The effective cost of the LPG = €0.93 liter to give the same milage as petrol.

So a diesel diging 25-30 mpg would save a fortune over 3 or 4 years.

When my circumstances change, and a rebuild would be considered in any event I can always put back the petrol lump.

What do you think?

You would never believe it.

I saw an ad for an SEC about 8 miles from where I live.

Called the guy and guess what.

He has a 1986 500 SEC with a 6 cyl turbo Merc engine in it.

Has been running it like that for 6 years!

No more details but will post pics if I can get some.

Your LPG price is wild! About 35p litre in the UK!

__________________
Cheers, Neil

tell me about it, we get HOSED in Ireland