so i have acquired a 1991 350 sd super mint inside and out. w126


its mixing coolant and oil. an i was curious as to if the oil cooler could have just gone bad. car isn't over heating . that's question 1


#2 is, any of you gear heads know; if i can put a getrag manual behind the motor once its fixed. i have a 87 535i with a stronk manual trans in it. <--- if that's a no ill probably just turn it to the max the auto can handle and call it good. i had a small idea to drift it . ... watching to man euro vids. but i'd be happy with a comfy daily too. that was the initial plan.



any thoughts ? i hope you all been well. since i was here last.

A 1991 350SD is a w126 and not a w124

I think your car has a oil-to-air cooler and not a oil-to-coolant cooler but not 100% sure

yes 126 i will try to edit the post, i saw that .. i knew id get caught for it :p

Since there is a separate cooler for oil (as noted above) so the oil in your coolant must be there from somewhere else. If it is pink it would be transmission oil from an automatic transmission. Otherwise the culprit may be a bad head gasket or a crack in the block or head.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

How likely is a cracked blocked? I been surfing eBay for engines.

I thought the heads in these can crack. So I am ready to buy a new head casing. ..... I didn't ponder a block would be a issue

The heads rarely go bad on the 3.4L engines. The head gaskets do go though. Before block-shopping, look into rebuilding the head and redoing the head gasket.

Just a suggestion here, feel free to ignore it: The 350SD is the second lowest volume W126 ever made. If it really is a nice condition vehicle, it would be a tragic waste to tear it up to turn it into some sort of "speed racer" which it'll never be. The 3.4L engines have weak connecting rods and do not take well to being driven hard, so all you're gonna wind up doing is blowing the engine and making a rare car worthless. Just my 2˘...

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

It's very unlikely that the block or the head is cracked. Especially on the 350SD

Agreed. I don't believe I have ever seen a cracked block. I think cracked heads though are a more likely concern. Bad head gaskets are pretty common. I had one of these about 12 years ago. They are affectionately (sarcasm) known as the rod bender motor.

I believe the rods are bent from hydro-lock due to a leaky head gasket or due to soot buildup. If I had one with problems I would not be reluctant to swap in a three liter version of the same motor.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I'll look for 3.0 as well . Till I see what can of worms I open up, possible to put 3.0 rods in this engine ?

No because a 3.0 crank has a shorter stroke and therefore has to have a longer rod and if you put a longer rod on a 3.4 crank then the piston will hit the head

What's the stroke difference?

Don't remember but the 3.4 has a longer stroke and a wider bore.

Mixing rods/pistons/cranks from engines with different dimensions is not always a great idea.

Most 3.4 engines are actually not bad and if it was my car I wouldn't mess with the internals of it.

Just fix the head gasket and you should be good to go.