# Leaking Hydraulic Lines?



## oldmankent (Mar 2, 2001)

Just replaced my hydraulic lines on the plow. Also took off all the fittings and cleaned the rust off of them. Since then, I've had a few leaks from the fittings and lines. I've hesitantly been using teflon tape to stop the leaks, although I'm afraid it might damage the pump. Do you guys use teflon or the pipe dope stuff?


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## snow warrior (Feb 4, 2005)

I WOULD USE A PIPE DOPE W/TEFLON and im a plumber


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## Bolts Indus. (Dec 22, 2003)

Never use teflon where there is petroleum based products involved.


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## oldmankent (Mar 2, 2001)

Bolts Indus. said:


> Never use teflon where there is petroleum based products involved.


So what do you use Bolts?


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## Mower For Less (Nov 2, 2004)

I think bolts meant tape, not teflon. The pipe dope with teflon that you apply as a paste should be fine because it dose not solidify. Also, I used to work in the plastic injection molding industry for 10 years, and alot of the mold shops would use a silicone sealant for the hydraulic threads (similar to a RTV sealant for automotive use).

Kevin


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## dforbes (Jan 14, 2005)

Bolts Indus. said:


> Never use teflon where there is petroleum based products involved.


They make a teflon tape just for this application. It is yellow instead of white


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## oldmankent (Mar 2, 2001)

dforbes said:


> They make a teflon tape just for this application. It is yellow instead of white


That is good info.


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## SnoFarmer (Oct 15, 2004)

If your using hydraulic fittings and not pipe fittings then you would use NOTHING... you should never need to use a sealant on a hydraulic line (fitting).
The hydraulic fittings are tapered or thay have a O-ring, the threads do not make a seal. If they are leaking it's because there 1. loose 2. bent .3. the o-ring is bad.



My $.02


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## oldmankent (Mar 2, 2001)

SnoFarmer said:


> If your using hydraulic fittings and not pipe fittings then you would use NOTHING... you should never need to use a sealant on a hydraulic line (fitting).
> The hydraulic fittings are tapered or thay have a O-ring, the threads do not make a seal. If they are leaking it's because there 1. loose 2. bent .3. the o-ring is bad.
> 
> My $.02


Yeah, some of them are tapered hydraulic fittings, but they were still weeping. It is entirely possible that I just didn't tighten them enough. I figured they were not supposed to have anything either as they were tapered fittings, but what do I know. I was very wary of overtightening and breaking something. Anyway all leaks are at the moment gone. We'll see how she does with this storm Monday afternoon/night on Tuesday morning.


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## snow warrior (Feb 4, 2005)

Bolts Indus. said:


> Never use teflon where there is petroleum based products involved.


wrong im a plumber for a gasoline company and that is what u use on petroleum


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## snowgm (Jan 24, 2005)

I've been in hydraulics for >10 years, just so you know I'm not making this up...

For NPT (pipe / tapered) fittings you MUST use something - preferably the white teflon tape. Pipe dope is not recommended (though commonly used) for hydraulic systems because it can get into the system. A lot of people (and OEM's) use it though because its easy to apply quickly. Yellow teflon tape is for gas lines as I recall.

All you have to do with the tape is keep away from the ends of the fitting (like 2-3 threads). Without the tape it will ALWAYS leak.

If you tighten it too much you will likely crack the manifold your screwing it into.

NPT sucks (its not even recognized as a proper high pressure fitting by SAE anymore)- thats why some of the plow manifolds are going to O-ring boss fittings.


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## SnoFarmer (Oct 15, 2004)

snowgm said:


> I've been in hydraulics for >10 years, just so you know I'm not making this up...
> 
> For NPT (pipe / tapered) fittings you MUST use something - preferably the white teflon tape. Pipe dope is not recommended (though commonly used) for hydraulic systems because it can get into the system. A lot of people (and OEM's) use it though because its easy to apply quickly. Yellow teflon tape is for gas lines as I recall Without the tape it will ALWAYS leak.
> 
> ...


 Then there would be tape and goop all over my new $200,000 piece of equipment??? for what it's worth I've been in the hydro field \ equipment operator\ supervisor for 24 years now, and have been to bombardier for training on there hydrostatic equipment. There is no tape or goop any where,,,
and NPT fittings are alive and doing very well (very common still) and any good SAE mechanic would recognize one right a way..Recognized and used in NEW applications every day.. :waving:


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## snowgm (Jan 24, 2005)

I didn't mean to say they weren't being used. They are still the standard on a lot of equipment. The fact is they shouldn't be used. Straight thread fittings (SAE/BSPP/ISO) are much better. But when everybody is used to something - its hard to change.

There is such a thing as NPTF which is a "dry-seal" thread that theoretically doesn't need tape - but its a one-shot thread (supposed to be). There are also fittings with a coating (usually plugs) that replicates the teflon. I don't know what Bombardier uses - so I can't speak to how they avoid using sealant on a tapered thread that has a leakage path. It isn't messy or anything - if its properly applied - so you shouldn't see it until you take the fitting out.

I just know with the all the stuff I've ever supplied to Caterpillar/Bobcat/John Deere, etc. I would be smacked around if I tried to put pipe thread in my blocks. They are all either SAE J568 (o-ring) or this stupid new ISO metric O-ring fitting (that nobody sells parts for except Parker).

Its still the easiest to service because everybody and their mother stocks pipe fittings - so there are a lot of reasons to keep using it on snowplows...

To be fair - I just thought of two good things about NPT - they are cheap and can be reoriented without swivel fittings.


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## SnoFarmer (Oct 15, 2004)

O.K. On a piece of heavy equipment there filters are large so some tape clogging them is no big deal.(really?)
ON your plow your hyd oil filter is small, so just a little tape and some goop, (witch does not dissolve) through in some cold temps and your :crying:


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## oldmankent (Mar 2, 2001)

Well I think I'm still leaking after this little storm. I will have another go around with the threads when the weather clears up. Kicker is, the old lines were not leaking at all, but they were looking a bit worn, so I figured I'd be safe to change them rather than have one break in the middle of a storm. Murphy's Law.


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## SnoFarmer (Oct 15, 2004)

Are the threads bad?


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## oldmankent (Mar 2, 2001)

No, I don't think the threads are cross threaded or anything. I just don't think I've found the sweet spot yet. I'm gonna call the dealer and ask what they do. I had my girlfriend pick up a couple of fittings from them before the big storm and she mentioned that they had mentioned teflon to get the fittings good. We shall see.


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## jjdonovan (Nov 1, 2001)

*Special seals for hydraulic tapered joints*

Hello all,
Just my 2 cents of knowledge on leaking joints on hydraulic lines but not at the threaded mpt end.
All hydraulic joints will, over time will loosen whether from vibration or high and low pressure cycles. When this occurs the joint separation may allow for an area for moisture to stay trapped against the tapered sealing joints of the hydraulic lines and fittings. If the corrosion is deep enough all the tightening in the world will never stop the fluid from leaking.
Most people would one of two things...live with it until it becomes unbearable or replace the parts.
However there are special seals ...more like a metal cap called VOISHON SEALS. These seals are great to use on small and major corrosion tapered joints areas.
They beat replacing fittings or lines.
Help that this info. helps!
JJ Donovan :salute:


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## snowgm (Jan 24, 2005)

As far as the tape goes - you have to put it on right and in the right place. If it gets into your system you put it on wrong. The dope will more likely get into your system - and even if it doesn't harden it will still clog your filters. That said, everybody still uses it and it doesn't seem to be a problem.

JJ,

I couldn't find those on the internet - do you have any info on the manufacturer? I'd be curious to see those - I'm always looking for a new "fix" to a common problem.

Were you talking about the swivel between the hose and the fitting leaking? That's a good point - and at that point I guess its time to buy a new hose. I know some guys replace them each year with their servicing, its not that expensive. Of course, you shouldn't have to.


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## justme- (Dec 28, 2004)

SnoFarmer said:


> If your using hydraulic fittings and not pipe fittings then you would use NOTHING... you should never need to use a sealant on a hydraulic line (fitting).
> The hydraulic fittings are tapered or thay have a O-ring, the threads do not make a seal. If they are leaking it's because there 1. loose 2. bent .3. the o-ring is bad.
> 
> My $.02


4 someone puts on tape or sealent incorrectly or when it's not supposed to be used.

Remember NEVER more than 3 wraps of tape and ALWAYS wrap inthe direction so tightening the fitting tightens the tape wrap.


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## jjdonovan (Nov 1, 2001)

*for SNOWGM about Hydraulic seals*

Hello all,
The manufacture is "VSI aerospace tools"the seals are actually called,VOI-SHAN with the hyphen .
If you do a search in GOOGLE the first web site that pops up click on that site they have great info on those seals.
These seals work for pressure or vacum,we test vacum at atmospheres of 10X10-6...outer space vacum basically. These seals are great Parker has seal caps made out of a flexible material also.
Hope that this helps you!
JJ Donovan :salute:


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## snowgm (Jan 24, 2005)

Thanks JJ, I had heard about those but had never seen them anywhere. A great idea for a beat up JIC fitting.

Sometimes a little creativity is required to get fittings to stop leaking - I had an application with 300F ATF that we were using blue RTV (for transmission pan gaskets) on pipe threads in addition to tape. I wasn't very happy about it - but it worked. This was to fix a customers HPU that had been built by some hydraulic "professionals". ATF is a *****...


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