Remove intake to get to glow plugs 93 300d 2.5L - PeachParts Mercedes-Benz Forum

hobberslobbers · #1 12-29-2011, 02:37 PM

hi all:

i am replacing the gp's on my dad's '93 300D 2.5L and wanted to know if i will have to take the entire intake manifold off??? i have the crossover pipe off, but don't see how i am going to get to the rear gp's. is there a detailed DIY for the 2.5L gp replacement? i saw dieselgiant's write-up, but it is not model-specific enough.

vstech · #2 12-29-2011, 02:40 PM

DG's writeup is on the 603, which is very similar to the 602, and should apply. I would take the manifold off IF YOU HAVE HIGH QUALITY ALLEN SOCKETS! you will need both long and short wrenches to reach all the bolts.
I must stress HIGH QUALITY tools for this though... you don't wanna have to drill out one of the bolts if you strip the head...

hobberslobbers · #3 12-29-2011, 02:49 PM

thx vstech. yep, i have the right tools. i've done gp's on both my 82 and 83 and the access on those was a piece of cake compared to these. alright then, onward and upward. hopefully this won't involve too much swearing.

ah-kay · #4 12-29-2011, 05:45 PM

I can change all the GPs on a OM603 1-6 without removing the intake. You need to have all the universal socket joints ( 1/4", 3/8", 1/2" ), different lengths extensions, long screw drivers, magnetic pickup etc at you disposal. It is doable but you have to be patient.

I do not do reaming and I never had issues.

Have fun.

TheDon · #5 12-29-2011, 06:24 PM

Did you ream the holes and use anti seize?

oldiesel · #6 12-29-2011, 06:43 PM

you can without too much difficulty,change all the glow plugs on your 93 602 providing you have a 1/4"drive 12mm deep socket, a 1/4" drive u-joint and a couple of 1/4" extensions and a 10mm 1/4" socket.Mercedes was smart enough to make the nuts that secure the wires to the glow plug captive in the wire connector so they dont drop and get lost.I am not sure that you can ream the holes to remove carbon with the manifold on,my guess is that you can.I have not reamed mine, i have a 602 and a 603 those engines dont seem to have the problem with the stuck glow plugs that some of the later engines have so i have skipped that step.I am sure someone will chime in that i should have done but the lack of it has not caused any problem yet(4.5yrs on the 602) My years in the marine repair business have left me with the habit of anti-seize on everything and most certainly on any steel fastener going into an aluminum thread. Don

compress ignite · #7 12-29-2011, 07:32 PM

If I'm remembering correctly 04 Diesel did his with the intake ON ,in a Below
Freezing Garage,on an Illinois Winter Night.

vstech · #8 12-29-2011, 08:36 PM

the dieselgiant.com glow plug repair/test page is done on a 603, and he makes no mention of removing the manifold. he uses a fuel line section to start the new plugs into the head.
he does not mention his trick for removing them.

04 Diesel · #9 12-29-2011, 09:10 PM

Quote:

Originally Posted by compress ignite

If I'm remembering correctly 04 Diesel did his with the intake ON ,in a Below
Freezing Garage,on an Illinois Winter Night.

You are right, I did, but I had to replace them again. I could not figure out how I got #5 out, so I did not replace that one, but the car is fine now. I just dont see how I got #5 out before.

hobberslobbers · #10 12-30-2011, 08:56 AM

thx to all for your advice. i went ahead and removed the intake manifold in order to have access to ream the gp holes. good thing, because #2 and #3 were so caked up with carbon. it wasn't all that difficult.

post mortem: i checked the resistance at the harness before doing the project. only #1 and #2 tested below 1ohm. #'s 3 thru 5 gave me some crazy numbers (11, 84, 26 ohms). to verify that i did not have an electrical harness problem, i took readings on the gp's once they were out, and they confirmed the same values, so that was good. gp's #2, 3 and 4 were hard to unloosen initially, so i stopped and soaked them with PB Blaster for about 15mins. i didn't want to take any chances of twisting them off in the head. after successful removal, i took the extra time to ream the holes. quite a bit of carbon to say the least (270k miles) and i suspect these might have been the original gp's. i tipped the terminals with dielectric grease and the threads with anti-seize and reassembled everything. TIP: i recommend taking a few pics of where everything is located (linkages, wires, etc...) before beginning. i had to refer to mine when reassembling to see where everything comes up through the gaps in the manifold. good thing i did that. also, group your loose bolts by component during disassembly. there are a few sizes to contend with. at any rate, on a scale of 1 to 10, this project was about a 6 due to all the tools you need to have handy to get to all the bolts.

Summary: This is my 4th gp job. I did both my 617's and wifey's 606 earlier in the year. This one was similar to the 606 because the manifold, but was a bit easier. i ended up with about 5 hours total in the job, but i'm totally picky and work slow and careful. overall, not too bad. What's amazing about this car? It only had 2 functional gp's and started all the way down to 35˚F with no issues. Now the gp light cycles properly on the dash, started smooth this morning at 30˚, and my dad is a happy camper. All that is left this morning is a diesel purge and a fuel filter change.

dvalente · #11 01-02-2013, 06:26 PM

I know the info on this thread is a year old, but I felt a need to comment.
I had glow plug light issues starting as of yesterday on my 1993 300D. Wonderful time of year to be working outside on your car in VT by the way, it was all of 7 degrees this afternoon.
A little probing and I found infinite resistance on plug #4. Took a wild guess that #4 was the fourth one from the front of the engine, thankfully I was right. This was information I was unable to find anywhere and thought people might like to know. It seems the plugs are numbered 1-5 from the front toward the back of the car.
Double-checked the plug after removal to confirm it wasn't the wiring, the plug itself shows infinite resistance. Good news. Should be an easy fix.
While I was in there, I made sure the relay worked with the 6-pin plug detached, and it did. So all signs point to this plug being my issue.

New one will be in tomorrow, unfortunately only the dealer had one in stock. I could have paid them $35 for a bosch plug, but waiting until tomorrow for half that price for a bosch plug seemed to make more sense. It was getting dark anyway.

No reaming for me. Those things are too expensive. If I needed to do all 5 plugs I'd probably spring for one, but not for just one. Sounds like many people have had fine success not reaming.

Anyway, as far as taking it out, I popped off the cruise control box, unbolting the arm at the top. That left plenty of room to access #4 easily. I needed a 3/8" 12mm deep socket with a u-joint, and a 10mm socket with a short extension on a 1/4" snap-on socket wrench with a swivel head. Turns out on the '93, there are no washers or anything to drop. I did have my magnet on a stick ready, but there was no need for that.
After looking around at the other plugs, I don't think there would be any need to take off the manifold, unless you like buying manifold seals, or you have an oil leak and need them. It may take you a little longer to take the plugs out, but the entire job may be shorter if you're flexible and have a swivel and a couple extensions.

My two cents.