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Blue plastic caps. A familiar story.

Cmark

Senior Member
Joined
Jan 2, 2009
Messages
3,176
Location
Australia
Well it happened again. A plastic cap left in a line at reassembly led to a full day of troubleshooting and R&I to fix it.

And who was to blame this time? Me. I did it. Guilty your honour.

But what's the answer? I appreciate there are systems of work in aircraft maintenance where everything used in a repair has to be accounted for, and that's fair enough. Does anyone have any ideas to help reduce the chances of this happening without going to aviation levels of complexity and expense?
 

mg2361

Senior Member
Joined
Jul 5, 2016
Messages
5,060
Location
Pennsylvania
Occupation
Equipment Mechanic
I feel your pain. I too have mistakenly left a plug in job and what a headache:eek:. I'm curious, in what capacity was the plug used, hose fitting, drilled port? I too would like to hear what others do to avoid such a dilemma. I try to only use metal plugs, caps or Flange Lok for flange fittings (I know...$$$). That way you have to remove them to install a hose. If I have to use plastic caps I make sure they are large enough to go over the outside of a fitting for the same reason. If they are small enough to go into the hole of the hose/fitting then I can't visually see them. The only other time is if I have a component out and disassembled and I need to plug a drilled port, then plastic is the only way and then I have to rely on me to remember to remove it.
 

Cmark

Senior Member
Joined
Jan 2, 2009
Messages
3,176
Location
Australia
I'm curious, in what capacity was the plug used, hose fitting, drilled port?.

It's all to do with contamination control. Capping every line as soon as it is disconnected during a repair is nowadays standard procedure (pioneered I believe by Caterpillar in our industry, at least). Problems occasionally arise when one of the (sometimes dozens of) plugs aren't removed during reassembly.
 

kshansen

Senior Member
Joined
Mar 11, 2012
Messages
11,129
Location
Central New York, USA
Occupation
Retired Mechanic in Stone Quarry
Can't add much to what mg2361 says.

I recall one time, not saying it was only once but this one comes to mind, anyone familiar with the old 988 87A transmission pump and suction line and where that pump is located?

Well try removing and replacing that line in a machine that has spent years working in a quarry without any way to wash the machine before removing that line! The end that is attached to the pump under the rear motor mount has to be done by sense of touch only and just getting those four 1/2 inch bolts loose then tight again is not fun.

Anyhow got it all buttoned up and fired up the engine and tried to move loader and nothing happens. Forget how come I did figure out my screw up so fast but killed engine before the pump running dry failed. Unbolt pump end of suction pipe and managed to get that blue plug out and reconnected the line. Fired up a second time and guess what transmission works much better with oil under pressure! Also it was fortunate that I was working alone and machine was back outside ready to go to work before anyone showed up.
 

Ct Farmer

Senior Member
Joined
Dec 8, 2016
Messages
322
Location
Connecticut
If at all possible I try to use threaded caps/plugs so that assembly is impossible without removal. Where I can’t I used plastic ones with big tabs that really stand out.

With flange fittings cover or plug the bolt holes so assembly can't be done.

Also keep a check list as to the number of plugs. Sure it takes a few minutes but compared to tearing something down again it is small.

I can think of one mistake that was costly. Years ago we built a genset with a Isuzu 4JB1 on it. Dad is crazy about keeping things covered so with no air cleaner rags stuffed in intake. You know where this is going. Roll engine over to line up with generator. Pulled the rag at final assembly - only there was 2 of them. Ran but smoked badly. Since the engine was new we took it back to dealer. 2 days later got the bad news and the bill.

I do waste gate repair work on certain Audi turbos. It involves 19 plugs and caps. I use bright red but always worry that a tech will leave one in. A put a big tag on with plug number but...
 

kshansen

Senior Member
Joined
Mar 11, 2012
Messages
11,129
Location
Central New York, USA
Occupation
Retired Mechanic in Stone Quarry
CT farmer, the story of the rags in intake reminded me of one another guy at the shop had years ago.

He was doing service on a Mack truck. Drove it into shop and dropped oil oil filter then removed the air filter. As housing was dirty, truck was used in quarry full time so that was kind of a given. So Bill stuffed a rag in the intake pipe.

Yep forgot to remove rag and when he tried to start truck no go. Just cranked over and it dawned on him "Dam IT! the rag in the intake! Proceeded to remove intake pipe and then intake manifold, non-turbo engine. When intake was off sure enough there was some rag down inside the intake ports of a couple cylinders. A bit of time with pliers and turning the engine over to open valves and all seemed to be out. Reassembled intake and tried to start.

Dang it still no fire. About then we noticed it was not smoking out the exhaust while cranking, those old non-turbo Mack would puff nasty white smoke when first cranking before they fired. Cracked a couple fuel lines loose at the pump and no fuel while cranking. Long story a bit shortened discovered the truck had run out of fuel as it was shut off. Dumped some fuel in tank and primed fuel filters and it fired right up!

Always wondered if it had not run out of fuel if that old END711 would have just chewed up that rag and spit it out the exhaust on start up.
 

Old Doug

Senior Member
Joined
Oct 16, 2013
Messages
4,485
Location
Mo
One of my bosses wanted me to look at his snowmobile it wouldnt ideal right . After some time i found a blue rag stuck half way down one of the carbs.I dont have the answer but a little wake up deal once every so often helps.
 

JD955SC

Senior Member
Joined
Mar 13, 2011
Messages
1,349
Location
The South
I hate the blue plugs

We have to buy our own metal plugs but those are only good for threaded ones. Not as easy to get ahold of block off plates for flanged connections.
 

f311fr1

Senior Member
Joined
May 11, 2016
Messages
698
Location
Middle TN
Look at Anchor Flanges. They have non pressure metal block off plates. Flat and with oring groves.
 

RZucker

Senior Member
Joined
Jul 7, 2013
Messages
4,077
Location
Wherever I end up
Occupation
Mechanic/welder
Rags and plugs.... I could write a book. And no, I haven't done it (Knocks on wood) but have caught myself once or twice.
One of the best examples was a customer with a 333FT Wabco scraper, the front radiator went bad with a rotten core so they pulled it and had the core replaced. After the radiator was back in the machine it started to run hot, they replaced the water pump, thermostats, ran with out thermostats, blamed the radiator shop, etc.
Only then did they call me... The radiator guy warned me about the goings on and wanted to know what I found.
On that machine the radiator outlet goes right to the transmission heat exchanger, that was my first target... guess what? it had a fairly new Tee shirt covering all the water tubes. Total silence when I pulled that one out.
Got some other good ones too, like the smoked Allison rebuild the customers guy left a chunk of rag in the cooler return line (main lube line). And the Twin disc trans with rag material plugging the suction screen...
 

56wrench

Senior Member
Joined
Dec 4, 2016
Messages
2,074
Location
alberta
reminds me of the time I left a plastic cap in the turbo drain line of a 3306. started it up and the turbo started puking oil. removed the drain tube, pried out the plug and re-installed. once the oil was cleaned off it was good to go. took a while for the oil to burn out of the pipe though. another time, I was doing a top-end overhaul on a Minneapolis tractor engine where you remove the cylinder pairs off the crankcase leaving the rods sticking up out of the crankcase. the shop procedure at the time was to put rags around the rods to keep stuff from going down into the inside. you can see where this is headed. put it all back together and drained the oil but it quit running out after a few seconds. wtf? piece of rag blocking the drain hole. pulled as much out as possible, cut it off, and repeated until it was all out and the oil was drained. exceptionally lucky! if it had went into the front or the back of the oil pan it may have stayed there until it plugged the suction screen which would have been very bad. after that, I only used a whole friggin bed sheet to cover any exposed top-ends lol
 

Truck Shop

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Dec 7, 2015
Messages
16,556
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WWW.
Twice on this one-complaint low oil pressure high oil temp on 3406's. Recent engine work done on both engines by different dealer shops. Removed oil cooler intake tube from pump to cooler.
Chopped up blue shop towels plugging the cooler, plus stat, plus radiator, plus heater core.

On one of our Series 60's that was inframed by dealer, same thing happened. But they didn't find all of it the first time around so they got to tear it down a second time plus a radiator each time
and two driver compartment heater cores and two sleeper compartment heater cores. I didn't trust that all fibers were gone and didn't want trouble with the heater cores so I installed a fuel filter
that only has a screen inside on the feed hose to the heaters.
 

oarwhat

Senior Member
Joined
Dec 14, 2009
Messages
824
Location
buffalo,n.y.
We did the rag thing on a small cam Cummins. Fired up the engine and it ran fine. took it for a short ride and it was running rough. back at the shop I put it to the floor and out comes a rag on fire. I'll never forget that one.
 

John C.

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Joined
Jun 11, 2007
Messages
12,865
Location
Northwest
Occupation
Machinery & Equipment Appraiser
I've never found a good solution to plugs and caps and rags and any other thing used to plug openings. I've been using Costso paper towels for years if I didn't have anything else. The key on all this for me was to never assume there was nothing in an open hole. I just got in the habit of looking every time I put something back together.
I got called out on a Komatsu PC650 one time that was doing some awfully bad vibrations whenever a function was used. When I got to the site there was an independent mechanic there that I knew and he filled me in on the story. The owner had someone else pull the pumps and send them in to an independent shop for overhaul because he said my friend was too expensive. He had a different mechanic reinstall the pumps. When things went bad he called my friend who called the dealer and that's how I ended up out there. Those machines had big strainers on the outlet of the pumps so we pulled those first and all three looked like beat up stuffed teddy bears. It seems the rebuilder had stuffed rags in the suction ports and then taped over the holes. All three sets of pumps came back out and came into the dealer for teardown and rebuild all over again.
 

Truck Shop

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Dec 7, 2015
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My main thing about all of this-I do the work and everyone keeps there stinking hands off what I'm working on and don't interrupt me with frivolous horse sh!t and questions along with
worthless phone calls. At my age I do the job one time one time only------------One ping, One ping only.
 
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Truck Shop

Senior Member
Joined
Dec 7, 2015
Messages
16,556
Location
WWW.
And one more Item, anything that comes out of a machine shop/automotive machine never trust the machinist. Pickup a micrometer and check the work. I worked in automotive machine for
6 of my years, and learned to double check everything before and after. I have caught two cranks in my time that instead of being a .010 under on all journals one on one and two on another
were turned .005. and rod housing bores that were not a perfect radial finish. Just mt two cents.
 
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