500Espot.com

Confirmed that the lower half of the intake manifold is NOT a straight-through hole. However, the entire intake will need to be removed & disassembled so that I can install that oustanding EGR clamp (that I accidentally neglected to install ) into the hole, and to tighten up a vacuum connection to the brake booster hose, to stop the evident vacuum leak that it has.

This will hopefully solve the high-idle problem. It will also give me the opportunity to recheck all of the other vacuum connections as I reinstall everything. Looking forward to getting this solved and back on the road this week. If I'm able to get the time during this week's nights, I should have this done by Thursday or Friday at the latest. Whew.

Some photos of the culprit below.....

Cheers,
Gerry

Here are a few photos of the final assembly of the top end, from last Saturday evening.

Tonight, in just 2.5 hours' work, I removed everything on the top end except the bolts that hold the intake manifold to the cylinder heads. I'll take those off tomorrow night and re-do the intake manifold and throttle body assembly. Should be ready to go by the weekend, or next Saturday at the latest.

Cheers,
Gerry

Intake is out tonight. It took about 45 minutes to drain coolant and loosen the bolts holding the manifold on the car. Then I separated the air-fuel mixture unit from the intake, and then the two halves of the intake manifold itself.

I re-attached the EGR tube clamp that was loose, so it's 100% secure now. And, my other hunch was correct. The vacuum tube coming upward from the back of the lower half of the intake manifold (which attaches to the hose leading to the brake booster), was not quite finger-tight at the bottom where it screws into the manifold.

Lastly, I took my multimeter and CAREFULLY practiced adjusting the throttle position switch where it attaches to the side of the throttle body. I've got a brand-new switch on order, but it has to be very carefully and minutely adjusted so that it properly senses when the throttle body flapper valve is in the "idle" (closed), slightly open and "full throttle" (wide open) positions. You measure the resistance across the connector at these various points and minutely adjust the switch position with your fingers until you get it just right. You can see the adjustment in the photo below in the elongated screw slots. By adjustment, I mean about a 1mm range where it's correct.

When the new switch comes, I'll install it and re-adjust. This switch is imperative to be adjusted correctly so that it sends the idle control computer and the EZL the correct signal as to where the throttle body flapper is. This switch not being correctly adjusted could also have been a factor in my high idle issue I discovered upon reassembly.

One last thing. I did away with the complex MB ("Normetta") ring clamp that attaches the bottom of the intake air rubber boot to the top of the throttle body. I replaced it with an ordinary large US ring clamp, which is much less complex but does the job just fine. My reason for doing this is that although the MB clamp adjusts from the vertical position, it's very finicky and difficult to get to "bite" so that it tightens correctly. The US ring clamp adjusts from the horizontal position (meaning the intake/throttle body must come out to loosen it) but it's much easier to attach and tighten. And, frankly, taking out the intake manifold isn't such a bad job, as long as one only has to do it once every 10-20 years ....

Anyhoo, I'll take some photos of all this tomorrow night. I'm basically in a holding pattern until my order of rubber vacuum elbows comes in, though I can do some limited re-assembly of the intake over the next couple of nights. I'll use the extra set of intake manifold gaskets that came with the head gasket set that I had. Then, I'll start putting things back together. I'm confident that the high-idle problem will be solved. I'll use extreme/extra care in all of the reassembly of things, particularly for the vacuum connections. Just wish the order of rubber will get here. Hopefully by Friday, so that I can get the job done over the weekend !!

Cheers,
Gerry

Well, I am proud to say that my project has come to a successful conclusion.

On Thursday night, I finished rebuilding the intake system (after pulling it back out of the car earlier in the week) by replacing all of the rubber vacuum elbow connectors attached to the vacuum lines, replacing the throttle position switch with a new one (and adjusting it correctly), and installing a new idle air distribution hose that connects to the two hoses that go to the fuel injectors.

I installed the intake on Thursday night and tightened down the bolts, and left the rest of the install (fuel lines, throttle linkage, all vacuum hoses, spark plug wires, adding coolant, etc. until tonight. I took my time tonight and it took me about 2.5 hours to get everything back together.

Started the engine up and immediately it went to a "normal" warmup RPM. I was very happy and relieved to see this. I let the car warm up to nearly operating temperature in the garage, then shut it off and added a bit more coolant. The car was blowing quite a bit of white smoke and this concerned me a bit. I decided to take the car for a test run about midnight CDT, perhaps about 10 miles around my subdivision. Didn't want to go too far from home with such a freshly rebuilt engine. The car blew gobs of white smoke for about half that distance, enough that it concerned me that i was burning coolant somehow, either with the heads or the intake manifold. However, after the car fully warmed up, the white smoke stopped and I didn't see a trace of it anywhere. I believe it was just condensation (it was a very humid day here today) as well as burning off the new coatings on the intake and exhaust manifolds.

The car idled smoothly. Ran very well. Acceleration very smooth and no problems. Transmission shifting is a little rough. I'm going to have to adjust the modulator a bit to even out those shifts, but at least it's not "slamming" in and out of gear like it was when it was idling high. Also I noticed that when it's in gear at idle, the vacuum gauge on the dash is just 1-2 millimeters off the peg. It should be ON the peg at idle whether it's in gear or not. This could just be an issue with the vacuum line that leads from the engine to the gauge, so I will have to check that out.

Other than the slightly rough shifting (I could live with it, but it's not as smooth as it was before I rebuilt the top end) I am very happy with how it all turned out. Very thankful that I licked the idle issue. I believe it was just a mis-adjustment of the throttle position switch, and perhaps a small vacuum leak or two.

Anyway, I hope this project serves as an inspiration to those of you who want to do some heaving projects with your cars. You can do it with lots of careful planning, the right tools and facilities, and lots of time and patience. There is really nothing more satisfying than to know that you did some major surgery on your car all yourself.

Hope all of you enjoyed this thread.

Cheers,
Gerry

Great job Gerry!

Thank you for takeing the time to share, nice work.

I love a happy ending

Seriously Gerry, thanks for taking the time to post this rebuild up! Couldnt wait for your daily !

Hope you need to do work on your other cars, so I have something to read!

BTW, your wife must be a saint

Nice work, Gerry! The two remaining small issues may be related. The tranny is probably shifting hard due to lower than normal vacuum, and the "economy" gauge is not on the peg for the same reason - slightly low vacuum. You may still have a minor vac leak somewhere in the rat's nest of tubing & fittings. If the tranny shifted fine before you started the work, I'd not touch the modulator adjustment until you rule out *everything* else. I think if you can get the needle back on the peg, the tranny issue may go away. I wouldn't worry about the white smoke as long as it doesn't return - probably a fluke.

I compared it to a friend's 560SEL. The vacuum is fine actually. It's pegging at idle in P, and slightly off the peg idling in gear. If I'm cruising along and let off the gas, it will peg to the left. All good signs. My friend's car is exactly the same.

I adjusted about one-half of the harshness out of it this morning with a simple Bowden cable adjustment in the throttle linkage.

Drove it about 30 miles this morning, and it's very very close to being all correct. Will be driving it up to Conroe, TX in about an hour (a 40-mile round trip) and that will all be via freeway (I-45).

Cheers,
Gerry

Supper SWEET Gerry, way to go man, PERRRRFECT !!!

A little more Bowden cable adjustment lowered the shift points too far, so I backed it off to where it was this morning. That was the appropriate adjustment and like I said removed some of the harshness out of the shifting. I will adjust the modulator a couple of notches tomorrow until I get the rest of it correctly.

Just as reference, the Bowden cable (back of the engine) controls the shift points & timing, and is a straight mechanical cable. The modulator (driver's side of transmission) controls the firmness and/or softness of the shifts themselves, and is vacuum controlled. Both are pretty accessible on the SEC.

I'm 98-99% done now. Just some fine tuning to do, and adding a few bundle ties in the factory locations to make sure everything is nice and cleaned up and stock-looking.

Cheers,
Gerry

P.S. In the near future, I'm going to have my indy shop put the car on a smoke machine, just to double check for there being no vacuum leaks. I think it would be well worth the 30-60 minutes worth of labor to do this.

GSXR, you were mostly right with regard to the tranny vacuum.

Solved the problem this morning. Noodled on it last night for a bit. One thing I observed: when I was reconnecting the vacuum line at the back of the motor (intake manifold) that comes up from the transmission, I noticed it was longer -- I could see more vacuum line than I could see before.

On a hunch, I got under the car to take a look at the modulator. The vacuum line was disconnected from the modulator !! That was the problem! So I pulled the line out from topside, and fashioned a brand new line from some spare vacuum line that I had. Reconnected that at the modulator and at the manifold, and took it for a test drive. PROBLEM SOLVED!

Got home and re-adjusted the Bowden cable back to where it was before, so that shift points were same place where they were before. Everything is rock-solid. Idles like a brand-new car

While I was under the car, I replaced the hard round rubber jacking points with new rubber pieces I had ordered. These are inexpensive and three of my four jacking points were cracked from age and use.

I am SOOOO excited that this project is now done, and the car is running as new.

Today is a day to relax, take a swim in the pool, and

Cheers,
Gerry

Gerry, thank you for sharing this rebuild with us all here on the board, I have enjoyed following along to the very successful conclusion.

When I’m down in Houston later this year for a wedding I will have to come by and take a look in person.

Russell

A few final photos.....

This saga is now complete. Drove the car to work today for the first time since the third week of February. Felt good!

Cheers,
Gerry

This thread reminds me of my intake manifold rebuild on my 420SEL. I didn't remove the heads, I did replace all the vacuum hoses and injector seals on the engines. I think my bad idle is caused by a misadjusted throttle flap on the CIS unit. BTW, the M116 in the 420SEL also uses the crossover pipe and EGR pipe.

Sure was a great experience. I know SO much more about how this engine and its' systems work. I am thankful to have a Gen 2 126 and not the earlier Gen 1 500SEC which had a more complex vacuum system. Even the 1986-88 560 engines were a bit different than the 89-91 cars in a lot of ways. Having an 89 is great.

Not a surprise WRT the 420SEL. Very similar to the 560 in many ways. The 560SL doesn't use the transverse pipe -- no room. The car is running very well now and it's quiet and smooth. I will change the oil soon.

To adjust your throttle body, you're probably going to have to remove the intake. Good time to also check your throttle position sensor and of course, double check all of the rubber donut rings and vacuum line attachments to the throttle body.

Thanks for your comments.

Cheers,
Gerry

Just an update on the car. I've driven it now more than 1,000 miles over the past 2.5 weeks since finishing the work and then the intake system take-off & re-install. The car has had a bit of a rough idle and when in P and N, intermittent high idle at 900-1000 RPM (at times it also idles at the proper ~600 RPM). The car ALWAYS idles at 550-650 RPM when in gear. However, the car is extremely strong running, tight, quiet, and is running efficiently (as a 5.6 with a 3.07 rear end can).

Extensive diagnostics were inconclusive as to the cause. I ruled out a lot of potential causes, but other things would require more extensive diagnostics (such as testing the fuel injectors).

Today I was finally able to check the lambda with a proper Bosch tester and zero out the mixture control at the proper level. It wasn't all that far off, and about a 1/4 turn of the adjustment screw was enough to get it right where it needed to be. Didn't affect idle RPM though, as I didn't think it would.

So, next up, I gave it a "smoke test" whereby smoke was injected into the intake system via the vacuum line going into the brake booster (line removed from the booster). That smoke test quickly showed some smoke coming up from inside of the intake manifold -- where the two halves of the manifold meet. These are supposed to be sealed by 8 rubber rings (1 ring for each intake runner). Evidently I didn't get a proper seal on one or more of the intake rubber rings.

So ..... for the second time (actually third time) I will remove the intake system, and take EXTREME care in re-assembling the intake manifold to ensure that there are no air/vacuum leaks (unmetered air) entering the system past the throttle body. The last time, it took me only one night to REMOVE the intake from the car, and two short nights (about 4-5 hours) to reassemble and reinstall it. I figure it will be about the same this time around.

It's not a horrible job, nor particularly tedious. Just frustrating that I have to do it again to get it all right. I will probably start on it this coming weekend, and take my time. Parts have been ordered (factory MB intake manifold gaskets are around $9.00 apiece, and I ordered a small MB cold start injector gasket (paper) for $0.69.

One other small thing is that the valve cover gasket on the driver's side is leaking, so with the intake off I'll loosen and reposition that cover, and tamp it down again with new crush washers.

Wish me luck. I'll probably do some photography along the way. Now that the Houston heat and humidity has arrived, I will probably do the manifold "rebuilding" inside of my house rather than in the garage, unless we get a string of more moderate and non-humid evenings. Which is rapidly getting highly unlikely.

Cheers,
Gerry

Found where the smoke was coming from - I hadn't seated one of the eight rubber donut rings that mate the two halves of the intake manifold together. The edge of one of the rings was bent over and wasn't sealing correctly.

Manifold is now pulled off the car and I'll disassemble (4 bolts) and replace the bad donut ring with a brand-new one on Sunday, then reassemble the intake manifold system & put back onto the car. New manifold gaskets in hand. Then I'll remove, re-seat and tighten the driver's side valve cover. It's leaking in two places - front and rear corners. BTW, the intake manifold gaskets (which I got from MBUSA this time) are made by OEM Elring, which also made the aftermarket head gaskets and intake manifold gaskets I used previously in the rebuild. I'll compare the MB Elring and aftermarket Elring gaskets for differences. The MB units have MB star and part numbers on them.

Removing, disassembling & reinstalling the intake manifold is about a 6-hour job -- 2.5 hours off, an hour or so cleaning and assembling things, and 2.5 hours to put it back on. It's a pretty routine operation for me now

Cheers,
Gerry

Here's what I found after removing the two halves of the intake manifold.

You can see the section of the rubber donut ring that was underneath (instead of around) the top half of one of the intake runners. This allowed unmetered air to be sucked into the system (essentially a vacuum leak), which caused about a 300-400 RPM increase in idle speed in P or N (in gear was fine). Interestingly, this phenomena was only observed when the engine was warmed up, not when first started cold.

I also took some photos of the old and new intake manifold gaskets, side by side. Both were made by OEM Elring (ElringKlinger AG) and are one of those situations where the parts are essentially identical except for the Benz part having the MB star on it. Interestingly the MB part was less expensive through parts.com than the aftermarket Elring part was that I purchased before. You really have to shop around between Benz and aftermarket parts suppliers to find the best deals -- this project taught me that often times, Benz factory parts ordered at wholesale can be less expensive than aftermarket stuff even by the same (or other high quality) OEMs.

http://www.elringklinger.de/pages_e/xfr ... _home.html

These manifold gaskets had around 1,200 miles on them. I was surprised to see the amount of carbon blackening on the surface of the air passages inside the heads, and the carbon blackening certain portions of the manifold gaskets even with only 1,200 miles. Interesting stuff.

Hopefully the third time disassembling the intake manifold system will be a charm, and it's all good. I triple-checked all of the donut rings (front and back) connecting the halves of the intake manifold. I will check it one last time before installing it on the car a bit later this morning.

Cheers,
Gerry

Wow, great job man.

Lovely write up.

Happy ending.

Everything went back together early this morning and I double-checked everything -- all connections, fittings, and so forth. Had to fasten the last couple of bolts that clamped the EGR tube to the exhaust manifold and to the rear of the driver's side cylinder head. Both are sort of a pain, and it was late last night, so I decided (after multiple attempts) to leave them until the morning when I was fresh. Luckily, I was able to get both of them within about 10 minutes this morning. It's amazing what a night's rest and a fresh perspective can do.

After that, it was just a matter of reconnecting the battery and double-checking that the vacuum line was still in place at the transmission modulator (it was). Following proper safety procedure, I did two things:

a) got two fire extinguishers handy and ready in case I needed them; and
b) didn't put the air cleaner on the car so I could observe to make sure there were no critical items like fuel leaks or so forth.

I am VERY glad that I did this. I started up the car after refilling most of the coolant, and turned the heater on HI as it warmed up. I ran the car for about 5-10 seconds and I stared smelling gasoline. I could see that the area around the driver's side of the fuel distributor was wet with fuel, and that there was fuel coming from somewhere. I immediately switched it off! Next, I got my trouble light handy and shined it on this area of the engine/fuel distributor. Then, I stared the car again, and observed fuel gushing out of one of the fittings where fuel went from the diaphragm pressure regulator (equivalent of the fuel pressure regulator) into the fuel distributor. I immediately switched off the engine again and looked more closely at the fitting. I could see that it somehow was loose and thus was not sealing correctly.

I removed the EHA (electro-hydraulic actuator) from the side of the fuel distributor and also removed a couple of the fuel lines to the injectors from the top of the fuel distributor to help me get better access to the big line going into the distributor that was leaking. I needed to be able to get two 17mm wrenches on there (one to loosen the fitting, and the other to serve as a counter-hold). Sure enough, the fitting that the counter-hold wrench was on was loose -- a good 2/3 of a turn loose. I carefully tightened it into the soft aluminum fuel distributor housing, held it with one of the 17mm wrenches, and tightened up the fuel line/banjo fitting with the other 17mm wrench. Re-attached the two fuel injector lines on the top of the fuel distributor, re-installed the EHA, and started up the car.

No fuel leaks. All good. The car started all three times right away, settled down into a 650-700 RPM idle as it warmed up and a 550 RPM idle both in gear and in P/N (remember that it had been idling at 900-1000 in P and N. The car is now running as it used to before the top-end operation. It's idling 100% smoothly - to the point where you have to really look to see if it is actually running or not.

The lesson learned for everyone is this: When you do any sort of work on the fuel system, make sure that you don't install the air cleaner/air box when you first start up the motor so that you can observe any fuel leaks or other issues that may occur as a result of your wrenching. If I had installed the air cleaner, there is no way I would have seen the fuel leaking from the fuel line into the fuel distributor, and there is no doubt that a fire would have resulted once the car was warmed up. So word to the wise - be careful when working with fuel !!

Took it out on a couple of errands and it ran flawlessly. Very very happy. VERY HAPPY. After three months' worth and fine-tuning, I am happy to say that this saga is now over, with happy results. It's amazing some of the idle characteristics that the un-sealed donut ring caused.

Now, it's time to change the oil on the E500 ....

Cheers,
Gerry

So, are you going with Royal Purple this time?

Actually, I happened to be at Wal-Mart on Saturday so I picked up 2 big bottles of the Mobil 1 5W-40 Turbo Diesel Truck oil (the stuff that GSXR recommends) -- it was on sale.

I'll go with RP on my next change.

Cheers,
Gerry

Great writeup Gerry.

Where is your Econ gauge now at idle in gear with A/C ON?

Mine is pegged left at idle.
But slightly off the peg in gear with A/C On.

You're showing totally normal characteristics in your ECON gauge.

There is no such thing here in Houston as AC being OFF. The AC pushbutton on my 560SEC is pretty much JB Welded into the "depressed" position. The big mass of gray JB Weld goo looks kind of yecchy on the outside of my pushbutton unit (kinda contrasts a bit with the burlwood, you know) but that AC button MUST stay depressed no matter what.

More seriously though, my vacuum gauge is the same in all cases whether AC is on or off.

At idle, it's pegged left.

In gear, it's about 1/8" to 1/4" to the right of the peg. Guess I should measure it with my micrometer to see how far it actually is....

My mechanic's 560SEL (in good health) is the same.

However, this isn't a failsafe method of determining whether vacuum leaks exist or not. A car with vacuum leaks can have these healthy characteristics elsewhere in the intake system (i.e. the intake runners, rubber boot, auxiliary idle air system, etc.). The vacuum going to the ECON gauge only comes off of one part of the system.

Conversely, if the ECON gauge DOES happen to be acting up, it can be that the intake vacuum system (donuts, boot, rubber hoses) is fine, but the four-way rubber vacuum splitter that contains the line that leads to the vac connection on the back of the ECON gauge is leaking.....

So you really have to check out the whole system. It's a good thing to replace all of the rubber vacuum fittings in the system (and on the transmission modulator, back of the ECON gauge, EZL, fuel vapor charcoal canister lines, etc.) as well as all of the vacuum lines to ensure the entire system is truly holding vac per spec.

Cheers,
Gerry

Gerry,

If a way was found to do forced induction do you think these rubber seals between the top and bottom inlet manifolds would seal?

Jim.

Yes, I think they would. The ends of the runners where they mate are very close together when the six bolts holding the two halves of the intake are tightened. The rubber is malleable enough that I think it would seal up just fine.

However, I don't have any real-world experience with this. I'd contact Jonathan Hodgman (jono@blueridgemb.com) to get his opinion on the matter, as it's likely he's got more experience with supercharging and turbocharging on these cars.

Cheers,
Gerry

Ok thanks Gerry.

Great thread; thank-you.

There is plenty of information about W126 performance over at Benzworld.org.

A couple of potentially helpful links there are:

General W126 section - http://www.benzworld.org/forums/w126-s-se-sec-sel-sd/

W126 performance thread (extensive) - http://www.benzworld.org/forums/w126-s- ... mance.html

Hope this helps.

My top-end rebuild has 4,000 miles on it now, and is running like a top. Will probably do my second oil change since the rebuild this coming weekend.

Cheers,
Gerry