subframe drop-'74 450sl

[jstreeter]

HI, just bought a '74 sl with a hole in the oil pan and fried con rod bearings. It looks like the easiest way to get the oilpan off and to replace the bearings would be to drop the front subframe.. i can replace the mounts at the same time. I understand the swaybar, the engine mounts, and the shocks and brake lines all have to come loose.
one question though: why remove the front springs? Is there some reason I have to do this? it looks like they will stay between the subframe and the lower control arm when I drop the subframe? any clues?
Thanks in advance for any tips.
-john

[230/8]

John:

I suggest you get a copy of the manual, either hardcopy or CD ROM. Job 33-100 describes the procedure for dropping out the front end. It is not complicated, just time consuming. You will need to fabricate a support brace for the engine because it mounts to the subframe. Once you are familiar with the whole procedure you can decide whether it is easier for you to drop the subframe or yank the engine.

CD ROMs here for $20 plus shipping:

http://www.classictechlit.mbusa.com/MB/

Lotsa luck...

230/8

[Chas H]

If the bearings are bad, most likely the crankshaft is too. The engine needs to come out to service the crankshaft.

[Roncallo]

Originally Posted by Chas H

If the bearings are bad, most likely the crankshaft is too. The engine needs to come out to service the crankshaft.

Yes what Chas H said !!!!!!!!. Dont even think about anything else. Best bet is a good used engine.

John Roncallo

[jstreeter]

it seems easy enough to pull the subframe.. i got all of the bolts loose in about 1.5 hours. Ill just pull the pan and see whats in there. as long as there is still babbit material left from the bearings, the crank should be OK. The cams are a little dull, but not scuffed. ditto for the cylinder bores (checked with a borescope)
I re-read the service manual a little closer ( I should have mentioned I already have it) it says you can leave everything together and drop it as a whole, if you want.. so question answered. if the damage is especially spectacular, maybe Ill take a picture and post it.
-john

[Roncallo]

Yes it can be pulled out all assembled see photo. Now since you plan on replacing bearings without crank and rods, can you please post the VIN number of the vehical.

motor weights

John Roncallo

[jstreeter]

John R,



excellent pic! thanks!

as for the vin:
why? why would I have to replace con rods (?!?!?), as they arent bent and the engine hasnt siezed? It turns freely and Ive never heard it run. All I have is a hole in the oilpan and a bit of bearing material. Theres still good crosshatching in the cylinders, and ive seen worse cams on another running 4.5. I havent even seen the condition of the crank to know if its ok or not... it just seems much easier to drop the subframe then to pull the engine? Even if i did mic the crank and replace the bearings, and then have good oil pressure, I wouldnt think it matters how it was fixed. And... Im not going to drive a unreliable car myself. Did you get the idea that im going to "flip" this car to some sort of unsuspecting buyer or something?
wow, that hurts, dude!

john

[Roncallo]

No I dont think your going to flip the car on E-bay. But I do think your about to learn an expensive and time consuming lesson the hard way. You did say you have 2 fried rods. Im assuming those are the 2 rods you can see through the hole in the oil pan which would be the two rods at the front to the engine. The front are the first two rods to be oiled. The problem will get worse as you go back. When you said two fried rods, I assume you mean black and probably smell like burnt toast. Do you really think these rods have retained there correct heat treat. With the bearing spun in the rod and the crank shaft banging arround in a hot oversized rod end, do you think the rod end bores are even round. And I'm sure the surface of your crank shaft is clean enough to eat off. It will work for a little while but not long.

I have herd the description form probably a thousand miles away. I dont need to hear any more or see any more. All I can say is dont do it.

John Roncallo

[jstreeter]

nope the rods look good from the borescope. everything looks good sofar... I just found 2 small pieces of copper in the oilpan. once I get the oilpan off, ill take stock of the situation... good point about the overheated conrods, though.. it will be the back 2 that reveal what has happened. it spins freely without any knocking, tho.. so it must have enough conrod bearing material to stop the knocking from a large gap.the 4 I can see look normal. if the back 2 look suspicious, Ill look for another 4.5...

[Roncallo]

Dont think it's like I never tried this. I'v done this on at least three occasions when I was 16 and bought a cars for $100 that I had to borrow $75 just to get the car. The results were always the same, a miserable failure.

[jstreeter]

oh man... this is car # 53 for me... im only 35 years old. IF you really want to feel my pain: I bought a maserati biturbo last year. Thats a whole 'nother level of pain over M-B. will report soon on 450sl progress or lack therof.

[jstreeter]

Well the subframe is so easy to take off, im glad I did it. The oil pan came off shortly thereafter. The # 4 main spun a bearing, and the number 5 main had shredded all of its copper. The other 3 mains and the con rod bearings look great, amazingly. They all still had oil in them. So, I replaced the subframe mounts, also easy, and put the subframe back in.
Then I got my engine hoist out and pulled the engine/transmission. about 7 hours .
The engine is on the stand, and the crank is about to be machined for oversize bearings.

One quick transmission question: Is the rear housing of the 3 speed removable easily? the previous owner also cracked the transmission mounting flange, and I need to get it disassembled to tig weld it.
thanks!
-john

[Roncallo]

Good to see your doing the right thing. On the 4 speed trans the rear housing comes right off without any trouble. I can only assume the 3 speed is similare.

John Roncallo