Most of the hoses for the cooling system of the 300SEL appear to be original, or quite old.  I wanted to replace these hoses with ones that looked original, or at least were the current Mercedes part.  Searching through the EPC to gather part numbers was rather useless.  There were many different part numbers for hoses that appeared to be the same, and nearly all of the part numbers turned out to be bad.  With the help of the classic center, I was able to come up with some length of hose in the necessary sizes.  For future reference:

  • 38mm: N 900271 038025.  This 38x46mm hoses is used on the thermostat housing.
  • 18mm: N 900271 018038.  18x27mm hose used for the heater connections
  • 12mm: N 900271 012018.  12x21mm hose used for several connections, including the injection pump and fan coupling thermostats.
  • A 340 501 02 82.  The upper and lower radiator connections use this short funny hose with a large bulge in the middle.
  • 46mm+: The connection from the water pump to the radiator is larger than the 38mm hose I had.  I still need to figure out the correct size for this one.
12mm Hose

12mm Hose, old and new

Today I managed to remove all these hoses and replace most of them.  You begin to appreciate just how complicated the M189 when you work on it.  There are a lot of hoses.  There are several very short pieces of 12mm hose associated with the fan coupling thermostat which are very difficult to get to.

I ran into a snag when I realize I didn’t have the right size hose for the large water pump connection under the manifolds.  Since I had already removed the old hose and the car would now be laid up until I could get the right size, I decided to take things a little further.

Looking through the radiator cap, I could see the core was pretty crusty looking.  So I pulled the radiator out and will have it cleaned up at a local shop.  While its out, I’ll have easier access to change the belts and and address the oil leak at the front of the engine.  Still lots of work to do!

More fine tuning

I’ve been thinking a lot about tuning the engine, and specifically, why it suddenly seems to run pretty poorly as of this past Wednesday.  I had let the injection pump soak with acetone again for a while, which didn’t seem to do much.  The engine was difficult to start, then would stall after it warmed up.  The idle was low and adjustment of the idle speed didn’t do much.

Out of concern for the problems it can cause, I first took apart the cold start valve.  Taking it apart was quite easy… just two screws hold the solenoid to it, and three bolts remove it from the manifold.  I confirmed that it wasn’t leaking fuel and the needle inside moved freely. I also confirmed that its a very good idea to replace its seals.  They were in very bad shape.  The small seal (A 001 997 75 40) is very expensive for a little o-ring, list price is $22.50.  The larger seal (A 002 997 52 45) is a value at only $3.  This is well worth the peace of mind.

Next started looking toward the thermostat on the injection pump used for warm-up.  It was clear that it didn’t work correctly since some air was being pulled through the little filter after the engine was warmed up.  I installed a new thermostat (A 001 203 95 75) and experimented with adding shims below it and it didn’t make any real difference in how the engine ran.

After thinking about it, the problem was quite obvious:  ignition timing.  When I removed the distributor to fiddle with the injection pump rack, I only eyeballed its position.  It turns out that it was WAY off.  I set it correctly and the difference in the way the engine ran was quite remarkable.

I ended up adding about 0.5mm of shims under the injection pump thermostat and it seems to work well now.  When running at operating temperature, no air is pulled into the warm-up system.  The idle speed adjustment screw works correctly and the engine idles smoothly at 800rpm now.  Throttle response is also much better.

To celebrate, I took the car on another trip around the parking lot:

As you can see, the car runs very nicely now.  There is no hesitation and it seems to have very nice power.

After this drive, I changed the oil.  It had already started to turn dark and I was worried it might be diluted with gas.  I also noticed that one of the front air bags began leaking, moving this job way up on the the list of things to do.

Radiator Cap

One of the difficult things when working on old cars is finding the right parts.  Even when they’re available, its not immediately obvious what is correct.  Since I’ve had the engine running, I’ve noticed cooling water leaking out of the radiator’s cap.  Although the cap looked good, I decided to order up a new one and see what came.  The new part wasn’t what I was expecting, but makes perfect sense.  These pictures show what was on the radiator on the left, and the new part (A 000 501 19 15) on the right.

000 501 19 15000 501 19 15

The issue is the way the expansion tank, which is unique to the sedans, is connected to the radiator.  There is a small hose running from the tank to the overflow connection on the radiator.  This means that any pressurized water in the expansion tank was pushed out of the radiator’s cap above the rubber seal.  The new cap seals at the top of the radiator, closing the system and allowing pressure to build.  The cap that is on the expansion tank is more like the one on the left (although its a larger size) and uses a spring to hold pressure in the system up to a point.

So, another minor problem solved!

Fine tuning

Now that the car is somewhat drivable, I can pay attention to getting the engine running well.  First step was to install a Pertronix electronic ignition kit to replace the dual-points in the distributor.  I’ve used these kits in previous cars with excellent results, so I was happy to see a kit (model 2865) exists specially for the M189 and it’s dual-point distributor.  Along with the pertronix, I changed to a Bosch Red coil (A 000 158 49 03) and 1.8ohm ballast resistor (A 000 158 17 45).  New wires and rotor are on order, but did’t arrive yet.  I won’t replace the cap due to the high cost, but the one on the car looks like its in good shape.

With the new ignition parts the engine ran better, but still not well.  I checked the cold start valve for leaks by removing the small bolt on it, as described on the old 300SE.org site.  No fuel came out after some time, so the valve doesn’t appear to be the source of the rich running.  I then disconnected the throttle linkage with the engine running and operated only the butterfly on the intake manifold.  The engine reved up quite a bit, confirming that its running very rich.  I shut it off and let it cool down.

Next step was to adjust the valves.  I’ve heard its possible for the intake valves to recede into the head quite badly over time, so I didn’t want to run the engine much more without checking them.  All the valves were tight, but not terribly so.  Adjustment was tedious, but I finished them all with the help of a friend in about 30 minutes.  A 14mm crows foot and good quality screw driver are a must for this job.

Now back to the fuel system.  According to several postings on the M100 message boards, it seemed likely that the rack in the injection pump is hung up from old fuel varnish that developed after years of sitting.  To free it, I used a bulb syringe to push acetone into the injection pump through the fuel line.  I used an extra fuel line that I ordered that normally goes on the output of the electric fuel pump, A 111 476 09 26.  This fit to the input connection of the injection pump and make it quite easy to fill it with acetone.

After soaking it a bit, I removed the small cover at the front of the pump to access the end of the rack.  This is a very difficult job because of its location.  Removing the distributor made it a bit easier, but a collection of long tools was needed to get in there.  I screwed a long M5 bolt into the end of the rack and check it for movement.  It move fairly easily, but didn’t return to its center position on its own until I moved it several more times.  Then I took this video to show its movement:

You can see it moves quite nicely here.  I put everything back together and ran the engine again.  Big improvement!  The engine reved up very easily now and idled much smoother.  However, once it warmed up, it would stall at idle again.  I think the cold start valve might still be an issue, so I’ll order up the seals and take it apart this week.  Just to be sure the injection pump rack can move freely, I filled it with acetone again to let it soak over the next few days.  This certainly can’t hurt!

Starting the engine

While my wife and son are visiting family out west, I’m able to dedicate an entire week of spare time that I don’t normally have to the car.  The first major task was for Wednesday evening:  get the engine running.  This required several smaller jobs be completed:

  • Install the fuel tank
  • Install the fuel pump and hoses
  • Install throttle linkage and ignition components
  • Top off or change basic fluids
  • Installed transmission linkage

These were all pretty straight forward tasks, except for installing the transmission linkage.  As some of my followers have said, the bushings are difficult to push on, and its not immediately clear how they fit.  This helpful photo from a friend explains it quite well.

The difficult part is press it onto the shift levers.  Specifically, the one buried deep in the transmission tunnel.  After some creative use of locking pliers, and about an hour of laying in awkward positions under the car, it was installed.  A special thanks to my friend Adrian for enduring this torture and successfully installing it!  This is the type of job that would have been much easier with a lift!

After everything was installed, we cranked the engine with the starter, but without spark plugs.  Oil pressure came up after a short time and we were ready to go for it.  In went 5 gallons of fresh gas, and 6 new Bosch W7DC spark plugs.

We cranked and cranked.  No firing.  We checked the fuel supply at the engine, then at the output of the pump… they were dry.  It seems that with the arrangement of the fuel tank and pump, 5 gallons isn’t enough to naturally flow in the direction of the pump, and the pump isn’t strong enough to prime itself.  The solution was to jack up the back of the car to help the fuel move forward, then run the pump with its output  running into a small container.  Once we had fuel here, we connected everything up again and confirmed fuel delivery to the injection pump.

More cranking.  After a while, it started to fire a bit.  It reminded me of starting a diesel in the dead of winter.  There was some fuel burning, but not enough to run on its own.  We  keep at it.  And just as we were about to give up and look for other problems, it started!  Rough, but it ran on its own.  It seems that it takes a long time to get fuel down to the injectors after all those years.  Here is the engine after running for a few minutes:

The engine sounds great!  We let it run long enough for the thermostat to open.  Oil pressure and temperature looked good.  It also smoothed out somewhat and no longer has a defined miss as in the video.

Everything was smoking a bit as the old nests and dust burned off the engine and exhaust.  We also seemed to have disrupted a mouse’s home in the exhaust system:

Overall, a greatly successful evening.  It ended up taking about 6 hours to do all of the above.

Fuel tank and fuel pump

I moved onto cleaning up the fuel system this week.  I was happy to find that the fuel tank was essentially empty, reducing the risk of a environmental disaster significantly.  Removing the fuel lines from the tank and fuel pump resulted in only a few drips of foul gasoline out of each.  Dropping the fuel tank out of the car was very easy… four bolts and a little prying and it dropped out.

I pulled the fuel level sender out and could see by the stains on it that the tank was probably about half full when it was stored.  It seems that if you leave about 10 gallons of gas for about 20 years, it reduces to about 1 quart of nasty brown stuff.  With the help of a friend, we poured what we could of what remained into an appropriate container.  Getting the last bit out it nearly impossible due to the location of the drain, fuel pickups, and filler.  Inside, its definitely rusty, but I’ve seen worse.  There is a local radiator shop that can clean it up for me.

Next, we moved onto the fuel pump.  Overall, it doesn’t look that bad from the outside.  We decided it made sense to remove the bottom cover of the pump to see if what crud might have made it inside.  There was some sludge and varnish, but it wasn’t too bad.  After soaking and flushing with some acetone I had handy, it cleaned up nicely.  Here is a look inside during the cleaning process:

We then briefly connected the pump to a battery to ensure that it would run.  The pump did run, but a bit unevenly.  It didn’t seem like a good idea to run it any more than a few seconds without any fuel in it, so I concluded that it works well enough to install back in the car for now.  I’ll order up a new seal (thats A 004 997 04 45, I hope) along with new fuel lines, a fuel filter, and tank screener.



Turning the engine, and other work

I spent about two hours working on the car today, mostly taking care of little things.  I replaced the heater hose eaten by mice, changed the oil and filter, and managed to get the battery cable off the positive post of the 1983 battery finally.  The oil was quite clean, almost red in color.  The bottom of the oil filter housing had some sludge, but I couldn’t feel much of anything with my finger in the bottom of the oil pan.  I was happy to see the filter was a nice German made one:

But the most important task of today was turning the engine:

Very exciting video, I know.  But it turned very easily.  I had already changed the oil, and poured a bit in each cylinder, on each cam lobe, the rockers, and around the chain tensioner.  This is very encouraging!

I then moved onto the interior and started to repair the wiring which was chewed by mice.  It wasn’t quite a bad as I thought.  Head light switch had 4 wires with the insulation chewed a bit, and about the same with the fuse box.  The two wires running to the switch inside the air suspension height adjustment box were the worst and will need to be cut back and replaced.  Lowering the fuse box down for inspection turned out to be a bit more of a project than I expected:  The B pillar cover, threshold plate, air suspension and hood release assembly, and the carpet in the foot well had to be removed to access the two bolts securing the fuse panel.  But it was worth the effort and piece of mind to know there is nothing that is at risk of burning or catching fire.

And finally, I took a closer look at the shifter bushings I need.  My parts guy gave me two to try, but I don’t think they’re right.  I can’t quite understand what holds the bushing and linkage to the shift lever.  There is no place for a clip of any kind, and the EPC doesn’t show anything.  Anyone have any ideas?  You can see the stub the linkage hangs on here:

I’ve been thinking about buying some short jack stands to support the car so I could climb under it.  Today I used a solution the worked very well, and seems more secure.  I took the cut 2x10s I had ready when we picked up the car and stacked them under the frame rail on each side of the front of the car.  When the car’s suspension is pumped it, the boards fit under without the need for a jack.  After the car sinks down a bit, it sits on the boards.  Removing them is easy, just connect the compressor and raise up the car.  I’ll have to cut more boards for the rear of the car when it comes time to drop the fuel tank.

Some discovery work

I spent a few hours after work today taking a deeper look at the car to determine its general condition.  I started by pulling the spark plugs and having a look… all were consistently carbon’ed up.  I then pulled the valve cover to have a look at the valvetrain.  I was quite impressed!

Everything looked quite nice, still covered with a thin film of oil.  There was still some oil pooled up in the tops of the head bolts making me wonder just how long ago this engine was last run.  I’d have expected sitting for over two decades would have dried things up a bit more.  The cam and rockers all looked good with little or no wear.  When I first saw the car, I thought I saw some fine metal shaving covering the cam.  Now that I’ve had a good look, I can see there are a few shiny shavings on the cam I can’t really explain, but its so little I’m not alarmed at this point.  Although its probably overkill, I poured a bit of a mixture of brake fluid and acetone into each cylinder to help free up any rings that might be sticking.

Next, I moved onto cleaning up the interior a bit.  There were several vintage plastic bags and random bits all over the interior.  The carpet cleaned up very nicely with just a vacuuming for now.  There were lots of small shells and other organic bits that were most likely leftover by mice that once lived in the car.  Surprisingly, there was no damage to the carpet.

Since I knew there had been mice in the car, I decided to pull apart the dashboard to inspect the wiring.  I removed the instrument cluster, radio, speaker, ash tray, and glove box.  As I suspected, there was a collection of paper and plastic bits just behind the instrument cluster.  A careful inspection of the wiring turned up a few chewed up wires running to the headlight switch.  It shouldn’t be a major issue to correct, but needs to be done before a battery is connected to the car again.  In addition, the speaker wires were broken and mostly missing.  It seems these wires are made of something far more delicious than the other wiring in the car!

I’ll have to go over the car again once more very carefully before connecting the battery.  The only other damage the mice caused were chewing through the line running to the oil pressure gauge, the top of one cooling hose.  The oil pressure line is quite a cheap part new from Mercedes, and all the hoses need to be replaced anyway.

The next step will be to get some oil in the cylinders and see if the engine will turn by hand.