A glow plug out ... plan of attack advice please - PeachParts Mercedes-Benz Forum

BodhiBenz1987 · #1 03-14-2011, 12:12 AM

I think the front end of my 87 300D was jealous of all the attention I paid to the back, because I've got a starting issue and a coolant loss issue (the latter I think is because the radiator leaks but I'm sending an oil sample out).
Anyhow, the starting issue looks simple: I checked the resistance of the GPs at the relay harness and sure enough #5 checks in at about 78 ohms. The car starts cold like it's only running on five cylinders, for about a minute, then puffs out a bunch of smoke and runs smoothly ... so that makes sense. Two questions: Do I try to get to that bugger without removing the manifold, or just remove the manifold and use the chance to clean it and replace the gaskets? And, if I do remove it, should I replace all six plugs on principle? The other five all read .8 ohms. They have about 42,000 miles on them and are Bosch. I'm leaning toward taking the manifold off, reaming and replacing all glow plugs.
Thoughts?

vstech · #2 03-14-2011, 12:25 AM

I'm leaning the same way as you...
good call.
then again, if you can reach #5 without intake removal, since we are heading into warmer weather, it may be a good thing to just pull that one, and save the intake cleaning and full GP swap for another, colder time...

JimmyL · #3 03-14-2011, 12:31 AM

If you currently have the disposable income to easily cover buying all new plugs then I'd go that route. If after all the rear suspension work and Muse expenses you want to pinch every penny for awhile, then certainly no problem there either.
If you only do one, and need to do another later, it only costs you effort......

BodhiBenz1987 · #4 03-14-2011, 12:32 AM

Quote:

Originally Posted by vstech

I'm leaning the same way as you...
good call.
then again, if you can reach #5 without intake removal, since we are heading into warmer weather, it may be a good thing to just pull that one, and save the intake cleaning and full GP swap for another, colder time...

I think I'll just buy all six tomorrow, then fiddle around with it. It looks like it'll be a beast to reach, but if it's not and I decide to just do the one, I can put the other five on a shelf. I've got many lovely swivel bits, but I want to be very sure not to break or strip anything!

BodhiBenz1987 · #5 03-14-2011, 12:36 AM

Quote:

Originally Posted by JimmyL

If you currently have the disposable income to easily cover buying all new plugs then I'd go that route. If after all the rear suspension work and Muse expenses you want to pinch every penny for awhile, then certainly no problem there either.
If you only do one, and need to do another later, it only costs you effort......

I always like pinching pennies ...

... but, since I'll probably end up buying all eventually, it wouldn't really hurt me to buy them all now. It's mostly a matter of how big a project I want to get into ... especially since my biggish projects tend to get bigger and bigger as they go on.

vstech · #6 03-14-2011, 12:46 AM

keep in mind, that removing the intake may require replacement of the injector clips due to breakage...
also, in rust belt, them tiny bolts break pretty easy... so use plenty of penetrant! Aero Kroil is SOOO much nicer to use and it's got a more pleasant odor over PB Blaster!

layback40 · #7 03-14-2011, 04:39 AM

Not wishing to be sexist in any way !!
Go get some of your nail polish remover & mix it 50/50 with atf , the SAE have shown this simple mix is many times better as a penetrant & seized bolt removal aid than any commercially available product.

The ohm test only shows if a GP is definitely bad. It does not show that the others are good. Only that they had the correct resistance. They still could have a bad heat pattern. Your idea of manifold removal is good. Best to remove & test with 12v on the battery all of them.

toomany MBZ · #8 03-14-2011, 07:51 AM

http://en.wikipedia.org/wiki/Nail_polish#Nail_polish_remover

layback40 · #9 03-14-2011, 08:43 AM

Quote:

Originally Posted by toomany MBZ

http://en.wikipedia.org/wiki/Nail_polish#Nail_polish_remover

I was referring to acetone.

kerry · #10 03-14-2011, 10:10 AM

Quote:

Originally Posted by BodhiBenz1987

I've got many lovely swivel bits, !

There's a thread over in OD devoted solely to that general topic.

vstech · #11 03-14-2011, 11:20 AM

Quote:

Originally Posted by kerry

There's a thread over in OD devoted solely to that general topic.

I was SOOOO tempted to cover that post...

toomany MBZ · #12 03-14-2011, 11:46 AM

Quote:

Originally Posted by layback40

I was referring to acetone.

I thought so, which is why I added the link, some folks may not realize they have much in common.

Junkman · #13 03-14-2011, 11:48 AM

Don't make work. Your glow plugs are new. Change the known bad one & see if you have easy starts. If we were going into winter or 2 or more plugs were known bad or starting is difficult after the change, I'd change them all. You likely have more pressing issues than messing with GPs out of season.

babymog · #14 03-14-2011, 02:39 PM

If you can change the bad plug with the intake in place, go for it. If you need to change two or more, order an intake-manifold gasket and make the job easy for yourself, the manifold comes off easily if you have a ball-end 6mm and/or a flex joint, and makes the whole job less painful.

If you find yourself in a pinch, NAPA can get the manifold gasket next-day, Elring, just costs a little more that way.

luke4 · #15 03-14-2011, 02:55 PM

In the vein of not fixing what ain't broke, IMHO, just change the offending glow plug. It's not that hard with the right combination of ratchet extensions and wobble joints and patience. And for getting the new one started w/o cross threading it, just shove the plug on the end of a piece of fuel line and use it as a flexible extension. It's also nice to use a little liquid graphite on the threads so it's easier to take out the next time.