Dave,

Thanks for the reply. Have seen several of your posts (including the removal of the EGR/ARV) and appreciate your knowledge and enthusiasm! I've been lurking here for a few weeks before registering this evening...

What does removing the EGR/ARV do for the car - other than reducing crud through the intake?

My indy says he replaced the radiator for the PO last year. The expansion tank is fairly clear and has yellow coolant - not sure about the silica pack. I just had him do a 150K maintenance and he refused to replace the coolant since it was fairly new.

As for the head, it's a "14". Does this mean I'm doomed? It doesn't use coolant. What is the high cold pressure to which you refer?

__________________
'87 300D 183K
'06 E320 CDI 10K

Hi again,

1) The EGR dumps crud into the intake and gums things up. It also reduces part-throttle power & MPG slightly. The ARV reduces boost at part throttle, to assist operation of the (now-removed, I hope) trap oxidizer, as well as the EGR. Disabling both can increase part throttle power, and overall MPG, assuming both systems were fully functional beforehand. There should not be a WOT power gain unless one or the other was acting up.

2) No worries on the coolant, yet. Watch that plastic tank though. Mine had some fairly large cracks on the back side, where you couldn't see it without removing it for inspection. I'd consider just replacing it at the next coolant change in a year or two. A new radiator is a GOOD thing, just make sure to keep it (and the condenser) free of bugs, leaves, dirt, etc.

3) The #14 head just means it's original and *could* cause problems in the future. Don't ever let it overheat and the head could last a LONG time. But don't be shocked if in a year or three you're stuck replacing the little booger. The first symptom is the "high cold pressure" issue. That means, with the car STONE COLD (after sitting overnight), squeeze the upper radiator hose. It should be soft & squishy, or even have slight vacuum (somewhat flattened). You should be able to pinch the sides of the hose together (like the cap was removed). If the hose has so much pressure that you can't pinch the sides at all, that's bad, and indicates a high probability of a minor crack. The car may run fine like this for quite a while but at that point, it's a ticking timebomb that eventually will need the head replaced. It happened to me and since then I've known of roughly a dozen via this forum and the MBZ.org diesel email list. If you have no pressure when cold, no coolant loss or 'usage', relax and enjoy the car.

Dave, thanks again for the info!

Trap is gone. Is the best way to plug off the two line on the left at the "H" vacuum fitting? I can't imagine more part-throttle power though. This thing has more torque than the law should allow. I actually wonder if I might be getting too much boost.

Will do on keeping the radiator clean. The temps seem to run a little above 80 on the gauge. Normal? Where do you get a new plastic tank? Dealership? No coolant or oil usage.

Car is cold now and hose is completely squishy - knocking on wood.... Only problems with the car seem to be soft, creaky seats and climate control system that blows out of all vents 7x24 - except the floor. Oh, and an outside thermometer that constantly reads 136 degrees F.

__________________
'87 300D 183K
'06 E320 CDI 10K

Hi Andy,

1) The easy way is to plug the lines at the "H" fitting. For a little more sanitary solution that will cost ~$10, you can order an "F" fitting. Either one works fine. The large black vent line connects with a coupling near the power brake booster - you can disconnect & cap it off there, and remove that section from the engine compartment. Photos of the two fittings are here:
http://www.meimann.com/images/mercedes/W124_stuff/smog_lines_plugged.jpg
http://www.meimann.com/images/mercedes/W124_stuff/2_port_vac_fitting.jpg
http://www.meimann.com/images/mercedes/W124_stuff/smog_solenoids.jpg
2) I doubt you are getting too much boost. But, you can always test that. Connect a pressure gauge with a "T" at the ALDA, run the hose+gauge inside the car through the window, and go for a test drive. Factory spec is approximately 12-14psi, and the overboost safety circuit triggers between 15-18psi (if it's working). Your 0-60 time should be in the 11 second range if you are near sea level, or at least below 2000-3000ft.

3) New plastic tank - dealership only (or Rusty, or Caliber), or FastLane can probably special order it for you.
http://www.meimann.com/images/mercedes/head_gasket/clean8.jpg

4) Temps a little above 80 are fine. Anything between 80-100C is normal. Anything below 80 and it's time to replace the t-stat or the temp sender. Above 100 with low load, or ambient temp, and something isn't working right in the cooling system.

5) Temp display - could be the sender is bad. It's a mild nuisance to replace, and costs about $50 for the new part.

6) You need to pull the glovebox, and test all 7 vacuum lines for the ACC pods. You'll need to replace leaky pods. Unfortunately, 4 of the 6 require removal of the dash - a major job. The owner's manual will explain where air *should* come out during heating and cooling, btw. You'll need a MityVac (the Silverline 4050 kit is awesome, works as a boost gauge too!) to test with. Here's a photo of the 7-port manifold:
http://www.meimann.com/images/mercedes/W124_dash/manifold_defrost.jpg

Thanks for all the info. The 0-60 was about 12 sec. with about 600 lbs. of passengers and cargo and 3/4 tank of fuel. So I guess that's not too much power after all.

It really feels pretty fast though - especially at 70 MPH/2800 RPM's - when it feels like there's a V-12 under the hood. Just a ton of midrange torque and plenty of acceleration without having to downshift. I actually wish it had a fifth gear that would put 70 MPH at 2000 or so. Might get more mileage that way.

__________________
'87 300D 183K
'06 E320 CDI 10K

That car will easily to 120 all day!

You need to fix the pressure line -- runs from the intake manifold to the switchover valve to the ALDA and then to the transmission amplifier. Need to have the little clamps on ALL the connections, else it tends to blow off. You won't get full boost unless the whole thing is pressure tight. There are some interconnections with the second switchover valve on the firewall, too. This is the cold running shift softening setup, so the tranny won't bang when cold

Should get you 0-60 in about 10 seconds running well. Milage is in the 30-32 mpg range, usually.

Fix the rest of the vac lines, too -- rubber connectors will be shot, it may also have serious leaks at the recirc valve and EGR actuators (both of mine are blown). The air recirc will reduce part throttle turbo lag and should increase highway milage since it cuts boost at light throttle. EGR can be left disconnected, but if you use synthetic oil won't cause any problems, and actually reduces combustion temps and heat load on the cooling system at part throttle.

The W124 300D is one of the bets cars MB ever made so far as I'm concerned!

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!