380SL Diesel Conversion Project - Page 22 - PeachParts Mercedes-Benz Forum

mach4 · #**316** 10-19-2012, 03:10 PM

In another thread (Trying to troubleshoot a rough running 617) I dealt with a rough running issue. It initially appeared to be something related to fuel delivery, but more and more it seemed to be due to my filled motor mounts.

I pulled the filled mounts out and replaced them with stock mounts as a test and almost all of my rough idling has disappeared.

I also fabricated a bracket for an engine shock.

Here's the original filled mounts that have been removed. (If anyone is doing any racing and have need of some "solid mounts" let me know - I've got a set on the shelf...cheap

)

I think that filling the mounts on this conversion is still potentially a good idea as insurance for collapsing mounts, but I say with certainty that Shore A 75 urethane is way, way too hard for this application. I'll probably try a 60 urethane, or maybe even softer, and will report back the results at that time. In the meantime I'll just monitor the mounts closely for any deterioration.

For now, I'm just enjoying a nice smooth idle.

mach4 · #**317** 12-06-2012, 05:34 PM

Having confirmed that the rough idle was due to my urethane filled motor mounts by installing a set of new ones, I decided to get a new set of motor mounts and fill them with a very soft urethane to see if that is the solution to keeping a smooth idle and yet preventing a collapse of the mounts. My original urethane was a Shore A 75 and the new urethane is a Shore A 30 which I sourced from Reynolds Advanced Materials. This chart shows the scales and some representative materials.

Compared to the original filled mounts the Febi mounts showed a permanent compression just within 3 weeks of use. So I'm going with Meyle for the new set. The Meyle are perfect for filling with urethane because the flashing from the casting of the rubber covers the sides and provides a perfect void for filling. Notice the difference below.

All that is necessary is to create a plug for the mounting hole that will contain the urethane. I used silicone mold release so that the plug could be removed easily. (Urethane is a great bonding agent) Here they are ready for pouring.

After pouring there is a 24 hour cure time.

The engine is out of the car right now for a transmission swap, so it will be awhile until I can report on the results of this latest motor mount strategy.

Here are the finished mounts

t walgamuth · #**318** 12-06-2012, 07:50 PM

As always, your workmanship is impeccible!

unkl300d · #**319** 12-06-2012, 08:01 PM

If its not too much trouble, could you recap why the motor mounts were predisposed for early collapse ? And also I am curious as to why you are swapping the trans. For one in better condition or a modified one ?

Thanks for the comprehensive updates.

mach4 · #**320** 12-06-2012, 08:26 PM

Quote:

Originally Posted by unkl300d

If its not too much trouble, could you recap why the motor mounts were predisposed for early collapse ? And also I am curious as to why you are swapping the trans. For one in better condition or a modified one ?

The thread that describes the transmission issue is here - 722.4 transmission now shifts from first to fourth

I recently sourced a spare engine and transmission and decided to replace the 722.4 with the stronger 722.3. It's a junk yard transmission so I've got my fingers crossed, but the fact that the spare engine runs really strong, I'm hoping the spare transmission is equally good.

The motor mount situation is described in this post - 380SL Diesel Conversion Project

When I put in the new stock mounts as a test, they collapsed to the point where in reverse I got some nasty vibration I believe was pan-to-subframe contact. I'm running with less than normal sump to subframe clearance, so I just can't tolerate any collapsing of the mounts.

If you search the threads you will find lots of motor mount issues... dramatically more recently with the cheap aftermarket mounts. My big picture choice is to modify the subframe or solve the motor mount collapse issue. I'm going down the motor mount path for now.

unkl300d · #**321** 12-06-2012, 08:56 PM

Thank you ! I was too worn out to go back and research before asking.

Makes sense now.
Good luck with the trannie !!

mach4 · #**322** 12-12-2012, 08:09 PM

Due to needing to swap in a new transmission, I now have the car running again with the new filled motor mounts.

I can definitely confirm that the softer urethane (Shore A 30) filled motor mounts work perfectly. The vibration at idle is gone and my secondary vibration between 1500-1800 rpm is also gone, which was due to the previously filled transmission mount.

I believe that this is a viable solution to the poor quality of aftermarket motor mounts that deteriorate and collapse very quickly.

Diagnosing and solving problems, and getting things dialed in can take a lot of time.

Ozarkdude · #**323** 12-19-2012, 11:22 AM

Ive read every post in this thread, and have to really tip my hat to you Mach.

I think I mentioned this elsewhere, but back when I owned our 380 SL, I was on another forum, not sure which (but not this one). I inquired about a swap of this nature and was totally ridiculed. Times change, and this was back in like 04 or 05 maybe, but at that time, and with such high fuel prices it seemed [to me] a logical choice. Especially considering the anemic power of a gas hog 380 motor.

Having owned several 300D and SD's (123,126), as well as W201 diesels, and doing a fair amount of mechanical work, it made sense the diesel shouldnt be to hard to wedge into the car. The only real obstacle that pulled the plug on my trying it was money, and the suggestion the hood wouldn't close. You have obviously proven that not only is there enough clearance and its a rather easy swap, but that it doesn't even have to be expensive.

I would also like to take this opportunity to say I am very impressed with this forum, as it is a breath of fresh air. Maybe times have changed, or maybe its just a different run of people, but its nice to see that everyone doesnt have their nose so high in the air they have to be snobby about how guys keep these cars running, get bent out of shape over mods we make, or become indifferent that some of us may not always have unlimited funds to do everything first class with all new parts.

All in all, you did really good converting that car and should be very proud of what you accomplished. A Mercedes SL roadster getting 30 to 32 mpg is like having your cake, and eating it too.

ROLLGUY · #**324** 12-19-2012, 08:29 PM

Quote:

Originally Posted by Ozarkdude

Ive read every post in this thread, and have to really tip my hat to you Mach.

I think I mentioned this elsewhere, but back when I owned our 380 SL, I was on another forum, not sure which (but not this one). I inquired about a swap of this nature and was totally ridiculed. Times change, and this was back in like 04 or 05 maybe, but at that time, and with such high fuel prices it seemed [to me] a logical choice. Especially considering the anemic power of a gas hog 380 motor.

Having owned several 300D and SD's (123,126), as well as W201 diesels, and doing a fair amount of mechanical work, it made sense the diesel shouldnt be to hard to wedge into the car. The only real obstacle that pulled the plug on my trying it was money, and the suggestion the hood wouldn't close. You have obviously proven that not only is there enough clearance and its a rather easy swap, but that it doesn't even have to be expensive.

I would also like to take this opportunity to say I am very impressed with this forum, as it is a breath of fresh air. Maybe times have changed, or maybe its just a different run of people, but its nice to see that everyone doesnt have their nose so high in the air they have to be snobby about how guys keep these cars running, get bent out of shape over mods we make, or become indifferent that some of us may not always have unlimited funds to do everything first class with all new parts.

All in all, you did really good converting that car and should be very proud of what you accomplished. A Mercedes SL roadster getting 30 to 32 mpg is like having your cake, and eating it too.

Others have said similar things about the quality of work done on this project, and I agree as well. Also agreed about this forum. I have had nothing but great experiences here, and could not have kept the Diesel MB's on the road without this forum. It has also been my pleasure to meet some of the fine folks that frequent this forum through the drives that my brother and I have organized: mbeg.webs.com. I believe that IF MB made a 300SLD, it would not be much different than mach4 has made it.....Rich

Ozarkdude · #**325** 12-19-2012, 11:49 PM

The only things I could foresee the factory doing different is making a more precision cross member and radiator support.

Anyone have any idea if it would be any more difficult to fit the 602 engine in to a 107?

mach4 · #**326** 12-20-2012, 12:42 AM

Quote:

Originally Posted by Ozarkdude

Anyone have any idea if it would be any more difficult to fit the 602 engine in to a 107?

Don't know about the 602 but the 603 and 606 are an order of magnitude more difficult.

charmalu · #**327** 12-20-2012, 12:51 AM

I found this thread with some SL engine swaps. I was looking for one that the guy did a 60X eng swap but can`t find it right now.

http://www.peachparts.com/shopforum/sl-forum/328287-sl-engine-transplant-possible.html

This thread was running last week.

Diesel SL

Charlie

t walgamuth · #**328** 12-20-2012, 05:47 AM

I have been here about 7 years or so. The amount of posts by purists who ridicule anything other than a factory setup are nil now but were pretty in the beginning. I suppose it is because of the age of the vehicles. As the cars get older the attitude of doing whatever it takes to keep them going gets stronger.

The methodical and thorough progression from idea to completed running car by Mach4 is extraordinary. His documentation of it and sharing of it has been extraordinary as well.

Thanks Man!

mach4 · #**329** 12-26-2012, 12:50 AM

Well I continue to come across some little problems related to the swap that just couldn't be anticipated. The most recent was my kickdown. I noticed that the kickdown wasn't working but this issue never came to the top of the heap. It was a minor annoyance. So I decided to tackle that project today. I checked the most obvious stuff first.

Made sure the pedal was hitting the switch properly... it was
Pulled the connector off the switch to test for power... none
Checked the fuse...fine.

So it had to be something with the power circuit and not the transmission or kickdown solenoid itself.

Checking the electrical diagram I noted that power to the kickdown switch comes from the EFPR (Electronic Fuel Pump Relay). I also noted that the EFPR needs a tach signal or it shuts down. This is to prevent the fuel pump from continuing to pump 70psi fuel from a damaged fuel line in the event of an accident. Not only do I not have an electric fuel pump, I don't have a tach signal to put on pin TD. So obviously my kickdown switch would never have power.

So the next step was to figure where the EFPR is located and how to get power to it. (It's located behind the glove box up against the firewall) The manual shows that jumpering pin 6 and 8 should get me what I need. However when I pulled the EFPR the pins were labeled 87k, 30, TD, 50, 31, 15 & 87. After much sleuthing I determined that the connector and relay correlation is as follows (herein documented for future use)

So I attempted to jumper pins 30 and 87k and plugged the EFPR back in and got a buzzing behind the climate module in the center console. From the diagram it looked like jumpering pin 87 and 30 might take care of the issue too, but no joy.

After careful consideration, I decided to gut the EFPR in much the same manner as I did with the glow plug relay (see post 223 from this thread 380SL Diesel Conversion Project ) and jumper the two pins properly. Here's the internals of the EFPR before removing the PCB.

Here is the gutted EFPR with pins 87k and 30 jumpered.

I plugged it in to test and it worked perfectly. No buzzer and good power to the kickdown switch.

Tomorrow I'll seal it with epoxy and fill with urethane and then install.

A very interesting troubleshooting saga and one more detail item ready to be crossed off the list.

mercmad6.3 · #**330** 12-26-2012, 01:47 AM

you do know of course that the kick down only requires 12 volts to activate?

So it would have been far simpler to just run a lead from a fused 12 volt source to the switch

. if you were to use a later trans from a W126 with the S and B switch ,it's just as easy with just an extra relay to activate the kick down when the switch is engaged with the gear lever. I dont know (without looking) if the US turbo engine uses the same trans as the regualr 300D because the 300D has a trans which must use 1st gear on takeoff. it's the only mercedes automatic which has this built in. It would be more road friendly in your 107 to have 1st gear take off. You dont feel it in a car with good trans,as the change into 2nd is almost inperceptible.