project "GM Benz" has begun... - Page 11 - PeachParts Mercedes-Benz Forum

LuckyEddie · #**151** 02-27-2009, 03:29 PM

Could you go with a sending unit from a SD they are electric and use a electric gage with it (marine?), Might need to change the plate that it screws into. I have been told by some mechanics that a Mercedes diesel blew up their OP gage I don't know the max bar that they run at but look at that.
Robert

JonL · #**152** 02-27-2009, 04:08 PM

Quote:

Originally Posted by cell

you know, for how indestructible and well engineered the rest of this engine is, I am a little surprised that something as critical as the oil pressure sending line is a simple push-on barb fitting, with nothing to secure it on the barb. although I suppose that's irrelevant if you just use the right size line.

There's not a whole lot of force on that line trying to pull it off the barbs. Assuming the ID of the tube is 1/8", the cross-sectional area is then 0.01227 in^2. Let's say you've got 150psi with high viscosity oil on a cold day... the force trying to separate the tube from the barb is only 1.84 lbs.

The proper tubing for the barbed fitting is a very tight fit. It's really hard to get it on the barb, I'd guess that even the minor diameter of the barb is larger than the nominal ID of the tube, so it is really stretched on there.

It's all academic now that you seem to have a line on an adapter that will allow you to choose from a bazillion electrical gauge and sender options.

cell · #**153** 02-27-2009, 04:43 PM

Quote:

Originally Posted by JonL

There's not a whole lot of force on that line trying to pull it off the barbs. Assuming the ID of the tube is 1/8", the cross-sectional area is then 0.01227 in^2. Let's say you've got 150psi with high viscosity oil on a cold day... the force trying to separate the tube from the barb is only 1.84 lbs.

The proper tubing for the barbed fitting is a very tight fit. It's really hard to get it on the barb, I'd guess that even the minor diameter of the barb is larger than the nominal ID of the tube, so it is really stretched on there.

Thanks for running the numbers and the analysis jon, -- that's what my hunch was so its good to see it confirmed. I love this forum

Lexxani · #**154** 02-27-2009, 04:57 PM

when I replaced my op line I used 1/4" id hard black emissions line ($3.50 at autozoo) and connected it to the two stock fittings. I was a little skeptical at first, but I put it on and could not pull the line free of the fitting. Its been on there for nearly a year now and works great, no leaks whatsoever.

MB wanted over $100 for the line and didnt have it in stock, I wanted to drive my car that day!. . .

cell · #**155** 02-27-2009, 05:16 PM

Quote:

Originally Posted by Lexxani

when I replaced my op line I used 1/4" id hard black emissions line ($3.50 at autozoo) and connected it to the two stock fittings. I was a little skeptical at first, but I put it on and could not pull the line free of the fitting. Its been on there for nearly a year now and works great, no leaks whatsoever.

MB wanted over $100 for the line and didnt have it in stock, I wanted to drive my car that day!. . .

awesome, thanks lexxani. my dealership wanted $54 for the line, and it had to be shipped from tennessee

KAdams4458 · #**156** 02-27-2009, 08:18 PM

Quote:

Originally Posted by cell

if m12x.1.5 is correct, it looks like this is what I want:

http://store.go-fast-parts.com/5700532.html

Auto Meter 2277 1/8" Npt to M12x1.5

Could be, but I aleady see a problem. That adapter seals with a crush washer, and the original fitting has a tapered cone seat of some sort. I think you're on the right track, though. That fitting pictured is just the sort of thing I used on my Saturn, but you need a tapered seat version to get it to seal on the Merc motor. They exist, as I have seen them. You might be able to get a crush washer seal there, if the area the seal would sit against is completely flat and smooth. Without looking at it, I don't have the answer.

The idea of just replacing the hose is a viable one, but you're right that it would still leave you needing to connect the hose to an aftermarket gauge. I thought of it, but didn't mention it because of the oddball hose. I feel that an adapter of some sort is the easiest way to go.

Edit: What I get for punching up a response hours and hours ago, but not finishing it and submitting it until now is an entire page of fresh posts.

That 1/4" plastic hardline from Auotozone idea worries me. It gets brittle from heat exposure. I used it on a vacuum system, and it fractured and failed within two or three years. The closer it is to a source of heat, the faster it goes bad. It's a pretty clever solution in this case, but I'd keep a close eye on it. Actually, I'd call it temporary. I don't think I'd trust that stuff for long.

cell · #**157** 02-27-2009, 08:47 PM

Quote:

Originally Posted by KAdams4458

Could be, but I aleady see a problem. That adapter seals with a crush washer, and the original fitting has a tapered cone seat of some sort. I think you're on the right track, though. That fitting pictured is just the sort of thing I used on my Saturn, but you need a tapered seat version to get it to seal on the Merc motor. They exist, as I have seen them. You might be able to get a crush washer seal there, if the area the seal would sit against is completely flat and smooth. Without looking at it, I don't have the answer.

The idea of just replacing the hose is a viable one, but you're right that it would still leave you needing to connect the hose to an aftermarket gauge. I thought of it, but didn't mention it because of the oddball hose. I feel that an adapter of some sort is the easiest way to go.

Edit: What I get for punching up a response hours and hours ago, but not finishing it and submitting it until now is an entire page of fresh posts.

That 1/4" plastic hardline from Auotozone idea worries me. It gets brittle from heat exposure. I used it on a vacuum system, and it fractured and failed within two or three years. The closer it is to a source of heat, the faster it goes bad. It's a pretty clever solution in this case, but I'd keep a close eye on it. Actually, I'd call it temporary. I don't think I'd trust that stuff for long.

Until my fitting comes in, I decided to block it off with a bolt and a nylon washer. The bolt is an M12x1.5 30mm long. The nylon washer is of the "extra thick" (1/8") variety.

Kadams: good thinking about the sealing method of the adapter. Luckily there is a flat "landing" onto which the crush washer should seal. However, as you mention, it needs to be very close to flat.

I actually ran into this type of sealing problem when I replaced the brake wheel cylinders on my truck. The "landing" area wasn't machined very flat. I filed that down, but was still having problems with getting a perfect seal (this was exacerbated by the fact that pressures inside your brake system can very high).

It was a this point that I learned about annealing copper crush washers before using them. Sure enough, my copper crush washers had been significantly work hardened during manufacturing.

The combination of filing the "landing area" smooth and annealing the copper washer resulted in success. I may have to do the same here -- this bolt + nylon washer will be an interesting test case.

http://67-72chevytrucks.com/vboard/showthread.php?t=251126&highlight=crush

cell · #**158** 02-27-2009, 09:02 PM

so, the vacuum system...

The vacuum pump has two main lines coming off of it.

this one goes to the master brake cylinder:

and I think this one connected to the air filter:

So, the one going to the master brake cylinder is obviously vacuum. However, what about the other line? Does the pump produce vacuum on that line as well? If I'm not using that line, do I need to leave it open, or stop if off?

cell · #**159** 02-27-2009, 09:05 PM

tranmission vacuum connections:

Is this the vacuum connection which controls shift hardness?

and this connection (the rubber boot attached to the tranny at the bottom photo of the photo) -- I can't remember if that was a vacuum connection as well, or if it was some sort of wiring connection:

jt20 · #**160** 02-27-2009, 09:07 PM

the vacuum pump is an engine as well. Its exhaust is pressurized air.

KAdams4458 · #**161** 02-27-2009, 09:56 PM

Quote:

Originally Posted by cell

Until my fitting comes in, I decided to block it off with a bolt and a nylon washer. The bolt is an M12x1.5 30mm long. The nylon washer is of the "extra thick" (1/8") variety.

Kadams: good thinking about the sealing method of the adapter. Luckily there is a flat "landing" onto which the crush washer should seal. However, as you mention, it needs to be very close to flat.

I actually ran into this type of sealing problem when I replaced the brake wheel cylinders on my truck. The "landing" area wasn't machined very flat. I filed that down, but was still having problems with getting a perfect seal (this was exacerbated by the fact that pressures inside your brake system can very high).

It was a this point that I learned about annealing copper crush washers before using them. Sure enough, my copper crush washers had been significantly work hardened during manufacturing.

The combination of filing the "landing area" smooth and annealing the copper washer resulted in success. I may have to do the same here -- this bolt + nylon washer will be an interesting test case.

http://67-72chevytrucks.com/vboard/showthread.php?t=251126&highlight=crush

That nylon may work for a short time, just keep a close eye on it. It likes to soften and bubble well before it reaches melting point, and I don't know how hot it will get.

You're spot on with the annealing. I don't generally make it a point to anneal new ones, but I will admit that I've been pinched with roadside and/or other time-sensitive repair situations where I had to reuse old copper crush seals. It works! It also comes in handy for the cheap Harbor Freight copper seals... Those things are so friggin' hard right out of the box...

KAdams4458 · #**162** 02-27-2009, 10:03 PM

Quote:

Originally Posted by jt20

the vacuum pump is an engine as well. Its exhaust is pressurized air.

Ditto. That "clear" line just gets pumped in to the air filter housing. Really, I think you can pump it wherever you want. It you vent it to the open, it would be a good idea to put a little filter on the end of it. It's the perfect size for one of nature's miracles to clog. (Mud daubers come to mind.)

cell · #**163** 02-27-2009, 10:30 PM

made it around the block again, this time without leaving a little black trail

vacuum is hooked up to the transmission, and I tee'ed in a hand vacuum pump to use as a gauge and it seems to be working.

unfortunately, something is limiting my speed to about 5 mph (the turbo isn't even spooling). I almost didn't make it back up the hill leading to my street

Perhaps my accelerator cable has slipped and the pedal is bottoming out before the linkage reaches its stop.

cell · #**164** 02-27-2009, 10:38 PM

I also noticed that disconnecting the vacuum noticeably raise the idle speed, which I thought was strange.

KAdams4458 · #**165** 02-27-2009, 10:41 PM

Quote:

Originally Posted by cell

made it around the block again, this time without leaving a little black trail

vacuum is hooked up to the transmission, and I tee'ed in a hand vacuum pump to use as a gauge and it seems to be working.

unfortunately, something is limiting my speed to about 5 mph (the turbo isn't even spooling). I almost didn't make it back up the hill leading to my street

Perhaps my accelerator cable has slipped and the pedal is bottoming out before the linkage reaches its stop.

cell, you not only have about the same tenacity as I do, you also seem to have the same luck for ending up with weird issues, too. We might be related.