Glow Plug and relay 84 300 SD - PeachParts Mercedes-Benz Forum

dannyF · #1 05-08-2008, 09:03 PM

OK, This seems to be a fairly common problem from my search of the posts. My GP light won't come on (as of a week or 2 ago) and now in the colder weather it takes a few painful cranks and turns of the key for my car to start. I will check the GP's, fuse and relay, but I probably ought to replace all the GP while I am at it. Does anyone recommend the kit that replaces the relay and the GP's and has a 3-minute time that it keeps the GP on to keep the engine warmer intitially for a cleaner start? I saw it available at Fastlane and it is Bosch manufactured.

Thank you.

Brian Carlton · #2 05-08-2008, 09:27 PM

You're getting a bit ahead of yourself there.

What's likely happened is that you've got one or two bad glow plugs and it's giving you starting troubles.

Since you're determined to change everything, then just do the glow plugs and you'll find that a fresh set of Bosch or Beru will give you superior starting performance.

You don't need the afterglow relay on the 617..........it's just money that's wasted..........unless there are other problems with the engine.

dannyF · #3 05-09-2008, 01:44 AM

OK, Thank you, Brian. I will go the slower route before I order and check out exactly which ones are wrong. Since I also run WVO I liked the idea of a longer glow plug 'on' time as I may be able to switch to WVO sooner after I start, but my car has had no major problems so I'll go the cheaper repair route and just replace the bad glow plugs presently.

Brian Carlton · #4 05-09-2008, 08:08 AM

Quote:

Originally Posted by dannyF

OK, Thank you, Brian. I will go the slower route before I order and check out exactly which ones are wrong. Since I also run WVO I liked the idea of a longer glow plug 'on' time as I may be able to switch to WVO sooner after I start, but my car has had no major problems so I'll go the cheaper repair route and just replace the bad glow plugs presently.

WVO is a completely different issue and might benefit from the extended glow.

You'll need a kit (afterglow kit) for that which includes a new relay and a set of extended glow plugs. I believe Fastlane offers such a kit............check with either Roy or Phil via telephone...........it won't appear on the website.

The cost is fairly substantial to get the complete kit at retail, however.

AdvisorGuy · #5 05-09-2008, 08:38 AM

I did my glow plugs 2 months ago. My problem was a rough,smoky idle for about 20 seconds after start up. Good idea to soak them with PB Blaster or equivilent for a day or two before you decide to remove them. I sprayed mine once a day for about a week before replacement and about an hour before I started. They all came out without a hitch. The only thing I disconnected was the throttle linkage from the firewall to make room for the Gear Wrenchs on #4 & 5 so it took me about an hour and a half. I just didn't want to disturb too much since it is 25 years old. Figured the less I disconnected the better. Turned out none of mine were actually bad. Just used JimmyL's reamer and all the GP holes were carboned up. 2,3 & 5 were particularly bad but since I had the new plugs at $13 each, I installed them. Glow for 5 seconds and it fires up with barely a second on the ignition to a nice smooth idle. Also, the squeaking you may hear when you're removing is most likely going to be the plugs against the carbon built up around the tips so don't fear you're stripping the threads as you're removing them. A little shot of PB once you loosen them will be fine. Good luck...

dannyF · #6 05-10-2008, 08:30 PM

Thank you Advisor Guy and (again) Brian,

Brian,

You were right - At least 2 of my plugs were shot, probably 3. Since I already bought 5 from the Dealer rather than by mail (hoping to complete this quickly.. ) I just decided to go with the Bosch, as were there originally. First 4 came out with some effort - last one behind the oil filter is a bear and I think the nut is stripping.... I tried all of my 12 mm wrenches (a regular, a ratcheting one, and my 12 mm socket won't fit due to clearance). I also sprayed some blaster. I believe this one is shot, too, and I want a new one in there. Any suggestions on how to get it out? May it be needed to actually remove the oil filter housing

? Advisor Guy, your idea of removing the throttle linkage is a good one, but I don't think it is enough now that this is stripping. Are there any ideas on how to remove this nearly stripped old, dead glow plug? Many thanks!

Brian Carlton · #7 05-10-2008, 08:41 PM

Quote:

Originally Posted by dannyF

Thank you Advisor Guy and (again) Brian,

Brian,

Are there any ideas on how to remove this nearly stripped old, dead glow plug? Many thanks!

I'd heat the plug with a propane torch for about three minutes. Then I'd allow it to fully cool. Then, I'd use either PB Blaster or Kroil on the plug and allow it to fully penetrate for 24 hours.

Then, find a six point box wrench and give the wrench a sharp hit with a hammer. Either you'll break it loose instantly...........or you'll fully strip the flats..........but, I'm betting on the former.

dannyF · #8 05-11-2008, 12:34 AM

Thanks, Brian,

but I do not have good blowtorch access to the GP area where I would need to heat with the blowtorch unless I remove the oil filter housing. If I do that, then I could probably use a socket, which may still work, depending on how badly I stripped the thing. Issue is - how hard is it to remove the oil filter housing?

I also considered trying to cut off the threaded end of the old GP (the piece that is sticking out). That would allow my 3/8 inch 12 mm socket to fit on the end, which it cannot do now and I do not have enough space for my 1/2" socket.

Because of my WVO system I also have coolant tubes running past this area, making access even harder. I separated one at the junction and caught the fluid, but this job became more work than I had thought as a result of difficult access....

Brian Carlton · #9 05-11-2008, 08:12 AM

Quote:

Originally Posted by dannyF

Thanks, Brian,

but I do not have good blowtorch access to the GP area where I would need to heat with the blowtorch unless I remove the oil filter housing. If I do that, then I could probably use a socket, which may still work, depending on how badly I stripped the thing. Issue is - how hard is it to remove the oil filter housing?

I also considered trying to cut off the threaded end of the old GP (the piece that is sticking out). That would allow my 3/8 inch 12 mm socket to fit on the end, which it cannot do now and I do not have enough space for my 1/2" socket.

Because of my WVO system I also have coolant tubes running past this area, making access even harder. I separated one at the junction and caught the fluid, but this job became more work than I had thought as a result of difficult access....

You need to make some room from the top. You'll need to get a box wrench down there...........and if you can do that...........you can get the tip of a propane torch down there.

Sure, you can remove the oil filter housing...........it's one big PITA.........and you need specific tools to do it in less than two hours. You also need to thoroughly clean the block face and remove every trace of old gasket material or you'll cause a leak with the new gasket. If you do go this way, get the OE gasket from the dealer and look up my posts for the best procedure for this task.

dannyF · #10 05-12-2008, 12:42 PM

Well, I sawed off the tip of the glow plug where the power goes and it allowed me to place on it a 3/8 " 12 mm socket. By clearing out the upper area (pulling out the throttle linkage, clearing assorted wires, vacuum lines, etc.), I was able to get a 90 degree swivel joint onto the socket and a socket wrench on top. The angle was such that it allowed the socket to get fairly snugly fit onto the GP nut by applying pressure from the wrench on top to the oil filter housing, which nearly blocked access to this GP. Fortunately, this GP was bad, too, otherwise the work would have felt in vain

. 3 out of 5 bad GP's!

Now, I just need to reinstall all the new GP's and put it all back together which leads to 3 questions.

1) Since I pulled out parts of the throttle linkage, is there a recommended lubricant for the ball joints on the throttle linkage? Now seems like a good time to grease things up.

2) A number of posts discussed "reaming out" the carbon buildup from within the GP sockets. Is there a special tool for this and do I need to be cautious of damaging anything inside that socket? Also, is this recommended?

3) Would application of dielectric grease or some other anti-sieze sort of substance be useful to put on the GP threads to make eventual removal simpler? Or, is that a bad idea?

Thank you all!

AdvisorGuy · #11 05-12-2008, 12:57 PM

Reaming is a definate recommendation. JimmyL is local to me and graciosly let me use his new reamer even before he himself used it. Like I posted earlier, 3 of the 5 GP holes were well-carboned up, pretty much to the point of completely surrounding the GP tips, hence my smoky,shaky idle. I'd suggest either buying one or finding someone local as gracious as Jimmy to borrow one from. You will definately get some serious carbon out of those holes. I actually ran the reamer in & out of the holes 2-3 times to get it all. Just coat the reamer with some bearing grease to catch most of the carbon. Before you install the new ones, have someone hold the STOP lever on the I/P linkage to shut the fuel delivery down and give the engine a crank for a few seconds to blow any loosened carbon out of the G/P holes before reinstall. As for anti-sieze on the threads, mine were original and they came out easily so I doubt I'll be replacing G/Ps again any time soon to worry about the threads..

Second one from the bottom on this link but the one Jimmy has seems much better, but you'll get the idea.

http://www.peachparts.com/diy/mb_tools/mb_tools.php?page=4

Brian Carlton · #12 05-12-2008, 01:03 PM

Quote:

Originally Posted by dannyF

Well, I sawed off the tip of the glow plug where the power goes and it allowed me to place on it a 3/8 " 12 mm socket. By clearing out the upper area (pulling out the throttle linkage, clearing assorted wires, vacuum lines, etc.), I was able to get a 90 degree swivel joint onto the socket and a socket wrench on top. The angle was such that it allowed the socket to get fairly snugly fit onto the GP nut by applying pressure from the wrench on top to the oil filter housing, which nearly blocked access to this GP. Fortunately, this GP was bad, too, otherwise the work would have felt in vain

. 3 out of 5 bad GP's!

Now, I just need to reinstall all the new GP's and put it all back together which leads to 3 questions.

1) Since I pulled out parts of the throttle linkage, is there a recommended lubricant for the ball joints on the throttle linkage? Now seems like a good time to grease things up.

2) A number of posts discussed "reaming out" the carbon buildup from within the GP sockets. Is there a special tool for this and do I need to be cautious of damaging anything inside that socket? Also, is this recommended?

3) Would application of dielectric grease or some other anti-sieze sort of substance be useful to put on the GP threads to make eventual removal simpler? Or, is that a bad idea?

Thank you all!

1) Lubricate the ball and socket joints with hydraulic fluid or transmission fluid. This should be done at every oil change to prevent too much friction in the linkage and wear on the ball and socket.

2) Whether it's required depends largely on the condition of the head and how the vehicle was driven. Some don't accumulate any carbon due to high speed driving and/or additive use.

3) You could use a dab of anti-sieze on the threads if you wish. It's not mandatory on a 617. If you're not a gorilla when you tighten them, they'll come out without a problem.