Newbie with engine problems (W126 500SEL)

[ben12345]

Well, where should I start...

I've a 1985 500SEL with an M117.963 that I rescued a couple of years ago from a farmers field. He said that the head gaskets were no good, but the car was very cheap, Had four brand new tyres on good bundts, and it was in black.
I drove with bad gaskets up until recently. They really weren't that bad, just had to keep topping up the water occasionally
Anyway,
I just completed changing the gaskets, helicoiled the block, had the heads machined, replaced all intake and vacuum rubber, replaced the headbolts, timing chain, guides etc...
But the problem persists. Maybe I should have had the heads/block checked for cracks at the time, but hindsight is a wonderful thing. The engine is now as smooth as silk though, and not using as much water, so its not all bad!
I think the best way forward from here is to just abandon the original engine and find a replacement. I'd like to 'upgrade' and put in a 117.968 High output 5.6 ie the 300bhp version , retaining my original intake, fuel injection and ancillaries.
Is this a feasible upgrade? Suggestions please on what I should do.

 

[Mikesmerc]

Bit of a tricky one, not sure if all the lecky bits(ecu etc) are the same on a 560. I would look further into where your loosing water. Check all spark plugs to see if there is any odd looking one. If the water was getting in to the any of the cylinders the head show show pitting or discoloration on the relevant cylinder when you had em off. Surely only one head can be at fault. Check oil for water. Could it be the heater matrix?, take her for a run till hot and park somewhere dry to see any visable leaks. Is she running at normal temp?
Rgds
Mike

 

[television]

You ask a hard one about the electrics,if you can get hold of the engine ECU for the new engine, it should just plug in.


Malcolm

 

[eric242340]

the old five sixty is one of the best engines Mercedes ever built. We used to say change the computer (Motronic) or change the engine. In the five hundred, pretty much the same. 5.6 engine will work ok, but you must have the right computer and engine wiring loom all of which are available anywhere in the world. And remember it must be motronic.

 

[ben12345]

Well,
Before I changed the gaskets, I did the old remove spark plugs trick and water sprayed from number 6 cylinder.
I'm pretty sure its a cracked block/head. If I use the car and then let it sit overnight, there is more than the normal amount of steam coming from the exhaust. If I however release the pressure from the coolant header tank straight after driving it, then I only get the normal slight amount of steam from the exhaust (remember its been pretty damp and cold here).
I threw some 'block seal' in there last night as a stop gap, we'll see how long it lasts.
If I remove the plugs, they all look clean, because I run on LPG 99% of the time.
The car used to creep up to about 100-105'C before doing the gaskets, now it stays at 80-85. No oil in the water or water in the oil as far as I can tell, and there didnt used to be even before I did the gaskets.

I thought all of the M117 engines in the W126 used K or KE jetronic, and never Motronic?
At the moment I have K jet (Full mechanical), and I'm pretty sure after 86 (when the 560 came out) they started to use KE jet (with computer).
So what I was planning is to use my existing inlet manifold/fuel injection system on the new 560 engine, so I dont have to go adding computers.
I have an Idle speed control box at the moment, but no fuel injection computer. All my fuel injection is done mechanically, and I'd like to keep it that way!

Kind Regards,
Ben

 

[television]

At the moment I have K jet (Full mechanical), and I'm pretty sure after 86 (when the 560 came out) they started to use KE jet (with computer).
So what I was planning is to use my existing inlet manifold/fuel injection system on the new 560 engine, so I dont have to go adding computers.
I have an Idle speed control box at the moment, but no fuel injection computer. All my fuel injection is done mechanically, and I'd like to keep it that way!

Kind Regards,
Ben

126s had K jetronic from 79-86 and KE jetronic 85-90.

I cant blaim you for keeping it that way,much easier to fix than a all in one computer, and why not change the manifolds, it will make it so easy.

Good luck Malcolm

 

[ben12345]

Yeah thats pretty much what I though. I didn't think they ever used motronic in a W126.
Well, the stop leak stuff I put in there seems to have worked so far...
I did have a hairy moment this morning on the way to work. The temp gauge went up to 110-120! I pulled over, took a look at everything, felt the hoses. All normal. Wiggled the coolant temp sensor wire, restarted the engine, and the gauge came straight back down to 80. Phew!

All as I need to do now is find a 5.6 engine for a good price!

Regards,
Ben

 

[television]

Good luck with the whole thing,they were one of the best ever made.
Some times when you use rad leaks addatives it can temporily block the system,but it does clear, anyway good luck with it.

malcolm