Best way to clean old glowplugs
 

Whats the best way to clean old glowplugs? Brake Cleaner, some form of alcohol etc? I'm assuming just scrubbing them with a plastic hard bristle brush in such a liquid would be fine?

- Peter.

I can't speak for everyone but this is my position. They cost about ten bucks each. They last two years or more. They are a PITA to remove and a PITA to put in. I don't like being stranded. I depend on my car though I have access to other autos.

For 50 bucks I'm not going through the trouble removing and reinstalling them. I want them to do their jobs each and every time I hit the ignition.

That being said, if I were going to clean one I'd want a soda in a sandblaster.

People here have mentioned a Mercruiser product that is apparently magical on carbon deposits, ... but I agree with the above, a good set of Bosch glowplugs is at my local Advance Auto, ... around $15/ea. For $100/ea. I'd be cleaning them.

Do not for any reason buy Autolite gps ,I pulled some that were not working in nov and was back in their this week doing the same job with the same plugs not working ,theyve got a racket going on.Sandpaper cleans the old ones followed by a wet rag.

I have to agree with everything above. The best way to clean old plugs is to dump them in the trash and replace with new Bosch plugs.

Even Bosch quality is slipping today. Beru is the best of the best.

For 100 bucks each I'd be reaming the GP hole twice a year and checking on them regularly. I'd probably replace only the ones which didn't work instead of a set every two years.

Getting red hot cleans them pretty well.

The Pencil type glow plugs can be wire brushed with a fine brustled stainless or brass brush by hand. Harbor Freight sells some cheap onse in a three pack. They remind you a bit of toothbrushes. You get a one nylon, one brass and one stainless stell brush.

I have not read of any method of cleaning the loop/filiment type Glow Plugs.

I have a different opinion than most here. I replace glow plugs when they burn out. There's no telling when a glow plug will burn out, new or used. Like a incandescent bulb, they burn out most often when powered up, when it is stressed the most.

To make changing glow plugs easy, I changed the wire lugs to quick disconnects that I can pull off in less than 2 seconds. On my 300D I can change glow plugs 1 to 4 in less than 5 minutes ea. #5 about 15 min.

I forgot to say it is also important to clean carbon out of the Glow Plug Holes. You can use a Glow Plug reamer or there it threads that have alternative methods.

Pics of your setup?

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Thanks!

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Thanks to all who've replied. Just for clarity's sake. My current set are Monark's I put in almost a year ago. They had worked fine till I messed up at least one of them when cycling my ignition on and off multiple times in a row to get my antenna up and down to clean it and lubricate it. As I still have the old ones I had removed last year I figured I'd try testing them to see which one is actually bad, and use the others as needed. But they are covered in oil from when I was extracting them so I want to try and clean them before actually testing them.

I did ream out the chambers when I did the job last year but there wasn't much carbon build up in them anyway.

I have the harbor freight brushes which I'll clean them with. How do you glow them out of the vehicle? Would using jumper cables from the battery positive terminal to the body of the plug work?

- Peter.

Monark plugs are not good. :( The injector nozzles are great, but not their GPs.

Yep, jumper cables CAREFULLY. Make the connection at the glow plug, not at the battery to avoid a Hydrogen explosion.

Yes you can use one jumper Cable terminal and ground the Body on the - terminal.
You want to see the Glow Plug get hot first at the tip and for the tip to remain the hottest part.

In the attached pic is a no good glow Plug. It is no good because it is getting hot in the center of the tip. That particular Glow Plug seemd good when I used the Ohm Meter on it but failed the visual test a cross the Battery.

battery negative to the area threaded into the head of the plug. battery positive to the terminal the harness wire connects to.

I recommend attaching the plug into a vice, and grounding the vice, then touching the positive to the terminal end...

whatever method you choose, keep in mind the plugs get hot enough to cook your hand instantly, do not allow ANY PART OF THE PLUG to touch you during or after testing!!!!!

I have had a couple go bad, and tried using my DMM to test them in the car, all tested within spec and there was no indication of a bad plug. I was able to determine which one by which cylinder missed cold, and removed to replace. Once removed I powered it up on the bench, compared it to a new Bosch, and could not identify the problem as they both glowed a nice bright red-orange quickly.

Maybe the above post where it is heating mid-plug more than the tip is the key here, but I feel that it is difficult to identify visually and will simply replace them if I have reason to pull them.

That being said, I have had several 602 turbo and 603 turbo engines, most with afterglow, hundreds of thousands of miles between them, and glowplug failure has been extremely rare for me, I've had two or three ever, and have never replaced plugs other than those failed plugs (and one set into a new head). They are robust and seem to last a very long time. ... now I'll have failures on both 603 cars (knocking on wood).

It's the power cycling of the glow plugs that shorten their lives. In that respect you will get longer glow plug lives with manual control. Instead of cycling the key multiple times to get longer glow times, you let the manual glow plugs glow longer (multiple cycles vs 1 cycle). If the engine is warm, don't activate manual glow, saving another cycle.

Wipe with rag then a brass wire brush from Harbor Freight. They are tough, you won't hurt them.

Update. What the hell I'm baffled.
 

So here's my troubleshooting results thus far...

Battery voltage into GP Relay 12.54V
Strip fuse 12.54V both sides.
Glow plugs front to back of engine, number 1 at front...
1 = 0.3 Ohms
2 = 0.2 Ohms
3 = 0.3 Ohms
4 = 0.3 Ohms

Inside the sockets for the glow harness connector.
1 = Nothing. No reading at all, as if I hadn't even connected the probe to it.
2 = 0.8 Ohms
3 = 0.8 Ohms
4 = 0.8 Ohms

With the ignition on and testing the each prong in the relay...
1 = 12.47V
2 = 12.47V
3 = 12.47V
4 = 12.47V

And I kept the probe on the tip of Number 1 prong till the relay kicked off and it immediately went to 0V.

I then tested the plugs that I pulled last year. They were Bosch made in France.
Three tested 0.3 Ohms, the fourth was 153 Ohms, so I marked that as bad.

Assuming that my problem was number one cylinder plug I removed it from the chamber and found it to be covered in carbon. I pulled number 4 as well and found it to have almost no carbon and completely clean tip.

I assumed that as the only discrepancy was the reading in the socket to # 1 plug that if I had both #1 and #4 outside the engine when I ran the cycle I should see # 4 light up and # 1 not. So I reattached the two plugs to their respective wires, held them in place with clamps in the engine bay so I could watch them and turned on the ignition.

The cycle lasted about 25 seconds and neither plug glowed.

I Used one of the old Bosch plugs that tested good in place of # 4 it repeated the process and still no glow.

So what is going on here? Am I looking at a new harness and or all new plugs?

- Peter.

when you say clamped in the engine bay... what do you mean? the plug body needs to be grounded or there will be no glow.

.3 ohms sounds low, I'd bet all plugs are bad. but it could be your meter.

I mean I removed # 1 and 4 from their chambers, re-attached them to their wires, held them away from the engine by clamping the wires in vice grips (softly so as not to harm them) and went thru a glow cycle.

I assumed they should work but if as you say they need to be grounded in order to work then that would explain the apparent lack of glow from them.

Strange thing is when I put them back in and went to work this morning the car seemed to start much more easily, no rough clattering and no clouds of smoke which seems to indicate normal glow operation again despite the glow light still not functioning.

I don't have time to troubleshoot more until the weekend when I'll resume my efforts.

My meter is just a cheap Harbor Freight one but it seemed to be giving apparently accurate readings. I might try to get a better one before continuing on with the investigation though.

- Peter.

The engine is grounded. What makes you think removing a glow plug and not grounding it and it should still glow?

Didn't realize that. As I said I'll have to return to the issue this weekend a bit wiser on the subject.

- Peter.

Don't bother buying a better ohm meter. Just continue the way you were testing which tests the whole circuit. Use battery jumper cables to ground the vise grip and make sure the glowing part of the glow plug is not in contact with any wires/ plastics when you power it up.

Hard to tell what you were doing but it sounds like #1 between harness connector and glow plug has a break somewhere.

Have someone start the car, while it is missing loosen the injector lines one at a time to determine which one is missing. This might take a few tries if the offending cylinder begins firing.

Everything else IMO is guessing. I only have experience with the 602/603 plugs, but I could not detect a significant difference in cold resistance nor in color of glow between the ones that were firing and the ones that were not.

Or, just buy a new set.

I had the negative probe on the bracket to which the fuel filter is mounted for ground, the positive probe inserted into each socket in the connector that plugs the plug wires into the regulator. It does seem like there was a break in the wire somewhere as the other sockets all returned the same reading of 0.8 Ohms.

But then as I said when I tried starting it again the last two mornings it started much more smoothly without any noticeable smoke and no clattering, despite the light not coming on. I don't get it.

But now I have another issue. About half way into my commute I start getting noticeable smoke emerging from the engine bay. I traced it to coming from under the air cleaner. So I'm going to have to work on that as well now. So, I guess it's back to the truck again until I can get this sorted out as well.

Just never ends I guess...

- Peter.