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Air compressor leaking oil

Dasgog

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The top of the deuce forum there stickies , search the the deuce parts spreadsheet thread.
Sorry to bring up an old thread but it is the exact thread I’d make again anyway...

My 72 M35A2 has a new leak and I noticed it at the bottom right corner of the air compressor where the prior owner apparently did use that RTV (sealant). Well the time has come that that no longer works. I tightened the bolts down again but to no avail.
If I were to buy/make a gasket for that bottom plate can it be removed, cleaned and replaced without taking the compressor off by removing the 4 bolts or would this require a complete removal.
 

Menaces Nemesis

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Sorry to bring up an old thread but it is the exact thread I’d make again anyway...

My 72 M35A2 has a new leak and I noticed it at the bottom right corner of the air compressor where the prior owner apparently did use that RTV (sealant). Well the time has come that that no longer works. I tightened the bolts down again but to no avail.
If I were to buy/make a gasket for that bottom plate can it be removed, cleaned and replaced without taking the compressor off by removing the 4 bolts or would this require a complete removal.
You're going to need to remove the compressor, which is no big deal, loosen the belt, remove the governor line, discharge line, the little bracket which holds the fuel injector return line away from the pulley (if it's still there), and the 2 nuts/2 bolts on the base. While you've got the compressor off, take the outer half of the pulley off and put a light coat of anti-sieze on the pulley threads. Also, disassemble and clean whatever intake filter element there is. After you reinstall and get the belt tight, be careful when you torque the bolts on the pulley outer half, tighten too much and it will crack (33' lbs is recomended max IIRC).
 

Dasgog

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You're going to need to remove the compressor, which is no big deal, loosen the belt, remove the governor line, discharge line, the little bracket which holds the fuel injector return line away from the pulley (if it's still there), and the 2 nuts/2 bolts on the base. While you've got the compressor off, take the outer half of the pulley off and put a light coat of anti-sieze on the pulley threads. Also, disassemble and clean whatever intake filter element there is. After you reinstall and get the belt tight, be careful when you torque the bolts on the pulley outer half, tighten too much and it will crack (33' lbs is recomended max IIRC).
hello, thank you for the response. I will admit I was hoping for the easy way out of this situation but I know I will be glad that I go through with it. going to have to verify what you mean by intake filter (on the Compressor I assume?) and then also the 33lbs... You mean the bolt that holds on the outer half of the pulley that squeezes the belt to tighten it?
Also aside from the obvious bottom gasket to replace is there anything I need to rebuild or fix?

also, please tel me I can loosen belt for compressor without having to take radiator out as the manual suggests.
 

Menaces Nemesis

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hello, thank you for the response. I will admit I was hoping for the easy way out of this situation but I know I will be glad that I go through with it. going to have to verify what you mean by intake filter (on the Compressor I assume?) and then also the 33lbs... You mean the bolt that holds on the outer half of the pulley that squeezes the belt to tighten it?
Also aside from the obvious bottom gasket to replace is there anything I need to rebuild or fix?

also, please tel me I can loosen belt for compressor without having to take radiator out as the manual suggests.
- Re; the intake filter, yes, there should be a little housing bolted to the compressor head where supply air is drawn into, sometimes a hose may be connected to it leading to your main engine air filter canister. Inside the little housing is typically a spring, porous/rigid filter element (that can be blasted out with something like mineral spirits or brake cleaner) and a stamped sheet metal ring between the two IIRC.

- Re; the 33' lbs, yes, the 2 ea. 3/8" bolts on the front pulley half that snug it to the pulley shaft. Usually it's a pain to get to at least one of them with a torque wrench, so you'll probably end up guestimating. Overtightened, the casting can crack adjacent to the relief kerf that the bolts span in order to snug the pulley up.

- Re; rebuild items, if you're not getting gobs of oil out of your wet tank (the lower one of the two) and you're building 120 psi within 3-4 minutes of starting with a drained system, you really shouldn't need to worry about anything other than the bottom gasket. If there is a gasket that needs to be replaced on the bottom of the little intake canister, you could easily cut one from gasket material from any auto parts store, or you could use silicone, sparingly, following the instructions to finger-tighten the components, let flash for a bit, and snug-up. From what I understand, if you're blowing bunches of oil, or struggling to make pressure in an otherwise tight system, buying a new compressor is probably what's needed as rebuild kits aren't available.

- Re; radiator removal to loosen belt tension, no, you shouldn't need to remove the radiator. However, be mindful that a new radiator is $1k anytime you're using tools around it. Many get by with using something like a big set of channel lock pliers and a good sized pipe wrench to loosen or tighten the outer pulley half, but the wrenches made specifically for the job, and available on eBay for $35 are nice to have.
 

M37M35

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Also keep in mind that since the compressor is lubricated with engine oil through the base, that you don't accidentally block the oil passage with excess RTV or if you hand cut a gasket.
 

Menaces Nemesis

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Also keep in mind that since the compressor is lubricated with engine oil through the base, that you don't accidentally block the oil passage with excess RTV or if you hand cut a gasket.
Since the compressor base gaskets are readily available, and not that expensive, I'd definetly go with a pre-cut one. Dry would be fine. If anything, you could treat it to a very light film of gasket sealant. Gasket sealants are very different than gasket makers (RTV). Contrary to popular belief, using RTV in conjunction with a gasket causes far more problems due to thermal expansion and contraction of dissimilar materials than it helps. Those who manufacture gaskets, sealants, and gasket makers, will most often state that RTV is not intended to be used along with a gasket, not intended to be a gasket dressing or sealant, nor should it be used as such. Check out # 10 on the top 10 gasketing mistakes...
https://www.permatex.com/ten-common-gasketing-mistakes/
While we're talking about using proper products for sealing, get yourself some good thread sealant paste or liquid and ditch the teflon tape when assembling the air connections. Typical white teflon tape isn't meant to be a sealant, it's primary purpose is to add lubricity to the threads to prevent galling of parts, primarily in household plumbing applications. True, it does help to seal by clogging threads, but a product like Permatex 80632 paste is an actual sealant, as well as adding lubricity, and it's intended to handle pretty much any substance on your truck; compressed air, oil, coolant, diesel fuel, etc...
https://www.plantengineering.com/articles/guidelines-for-choosing-a-pipe-thread-sealant/#:~:text=Strictly speaking, Teflon tape is not a thread,of the threads or it unravels and tears.
 
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Dasgog

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Since the compressor base gaskets are readily available, and not that expensive, I'd definetly go with a pre-cut one. Dry would be fine. If anything, you could treat it to a very light film of gasket sealant. Gasket sealants are very different than gasket makers (RTV). Contrary to popular belief, using RTV in conjunction with a gasket causes far more problems due to thermal expansion and contraction of dissimilar materials than it helps. Those who manufacture gaskets, sealants, and gasket makers, will most often state that RTV is not intended to be used along with a gasket, not intended to be a gasket dressing or sealant, nor should it be used as such. Check out # 10 on the top 10 gasketing mistakes...
https://www.permatex.com/ten-common-gasketing-mistakes/
While we're talking about using proper products for sealing, get yourself some good thread sealant paste or liquid and ditch the teflon tape when assembling the air connections. Typical white teflon tape isn't meant to be a sealant, it's primary purpose is to add lubricity to the threads to prevent galling of parts, primarily in household plumbing applications. True, it does help to seal by clogging threads, but a product like Permatex 80632 paste is an actual sealant, as well as adding lubricity, and it's intended to handle pretty much any substance on your truck; compressed air, oil, coolant, diesel fuel, etc...
https://www.plantengineering.com/articles/guidelines-for-choosing-a-pipe-thread-sealant/#:~:text=Strictly speaking, Teflon tape is not a thread,of the threads or it unravels and tears.
Awesome. Thank you all for the responses I definitely feel more confident in doing this. I can say that the only leaking is the bottom seal. Not gushing or anything but oil beading up at the seal and seems to spray out under load. But nothing in great mass.
I actually do have the 2 wrenches for the tightening/loosening of the belt so that’s a plus. I already removed radiator and ALL that when I had to replace my front crank seal and that radiator (installing) nearly had me in years solo gig. Heh.
So I’m definitely going to be delicate and careful around it.
I will get a seal pre cut and look into that sealant instead of the white tape.

thank you
 

Dasgog

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Awesome. Thank you all for the responses I definitely feel more confident in doing this. I can say that the only leaking is the bottom seal. Not gushing or anything but oil beading up at the seal and seems to spray out under load. But nothing in great mass.
I actually do have the 2 wrenches for the tightening/loosening of the belt so that’s a plus. I already removed radiator and ALL that when I had to replace my front crank seal and that radiator (installing) nearly had me in years solo gig. Heh.
So I’m definitely going to be delicate and careful around it.
I will get a seal pre cut and look into that sealant instead of the white tape.

thank you
Hello. Just wanted to mention, after some time, that I replaced the bottom seal and put everything back together and no more leaks, from there.
What I do notice is that there is still oil spraying on the IP and after further inspection it seems that the bolt on the (facing the Air Compressor from drivers side) right side where the bolt fastens the fuel lines to the Compressor is loose and when tightens fully it keeps spinning. To the point where when bolt is fully in and I pull on it it slides out. I took it out and out put some thread tape on it snd same thing. The bolt [hole] simply warmed and got too big.
That has to be where the oil is coming from. Would you recommend I get a bigger (as in like barely bigger) bolt or what? As I said the bolt goes all the way on and keeps spinning. The bolt itself is beautiful and fine threading so I’m quite certain it’s the bolt hole.
 

kenn

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Dredging up this thread. I'm still inspecting previous owner's/motor pool's handiwork and looking at a leak that is bathing the driver front area with a sheen of oil. As I look at it, it is very heavy around the base of the compressor so I'm assuming there is oil coming from there. The compressor is definitely a replacement unit as the paint is in better condition than surrounding parts and is a very different shade of green than everything else.

I'm going to have to clean up the area and remove/replace the compressor with new gaskets. Napa RN26GV was stated in this thread earlier. In looking at that part number, there are a LOT of gaskets in that set! What is in the NAPA set looks a little different than some of the vendors sets. Am I OK with this NAPA set?

I've looked at the pictures and it is a single cylinder. Please look at picture below. The base all around is soaked in oil and the engine block between the compressor and block is also very wet. I thought maybe it might be a front head gasket leak but I'm hoping this is all that is leaking... I'll tackle this one as soon as it cools a bit but please see the pic and tell me if you think this is likely leaking from the base. It also looks like the little filter housing thingy is leaking a little, too.
 

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kenn

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Let me make my question more clear:

Does anyone know the part number for the single cylinder compressor gasket kit? The napa one listed in the cross reference spreadsheet here is for the twin and won't work for my application since I have the single. It appears that only the bottom gasket is leaking and possibly there is a small amount between the filter and the compressor body but that may just be "splash". Either way, I don't need a huge gasket kit - just those two. I have read the -20 now several times so I'm ready to go minus the appropriate gaskets.
 

Mullaney

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Let me make my question more clear:

Does anyone know the part number for the single cylinder compressor gasket kit? The napa one listed in the cross reference spreadsheet here is for the twin and won't work for my application since I have the single. It appears that only the bottom gasket is leaking and possibly there is a small amount between the filter and the compressor body but that may just be "splash". Either way, I don't need a huge gasket kit - just those two. I have read the -20 now several times so I'm ready to go minus the appropriate gaskets.
.
It might be easier for you to go to the local NAPA or parts house close to you and buy a roll of gasket material. If by freak chance you take off your compressor and the gasket (or even if most of it) comes off whole, cleaning it up and tracing out the shape onto the new material will net you something to stop the oil leak.

The first time you look at the idea of cutting your own gaskets - the task seems almost impossible. I am here to tell you that it just isn't so. Better and with pretty edges is nice but it doesn't have to be. All you are doing is creating a "softer than steel or iron" pad to allow the possible imperfections in the two mating surfaces to seal to each other.

You need some scissors and a razor blade. An exact-o knife is a nice upgrade to a razor blade (thinner point) but either way will work. A small ball peen hammer could cut the outside edge - but that is a class called Gasket Making 2.0
 
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cattlerepairman

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What @Mullaney said! When I rebuilt my LDS I went through a few sheets of FelPro gasket material and I was cutting my own gaskets for the first time. I actually like doing it and have been cutting my own off and on ever since. There are videos (of course) to watch on YouTube (of course) with a few pointers.
Tracing is one way, placing the gasket material on the part and gently hammering along the edges with a hammer is another - the latter results in a "stencilled out" gasket that usually fits really well. Empty shell casings of various calibers make great hole punches for bolt holes or oil passages. Try it out and have fun with creativity!
 

Computerdoc08

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Let me make my question more clear:

Does anyone know the part number for the single cylinder compressor gasket kit? The napa one listed in the cross reference spreadsheet here is for the twin and won't work for my application since I have the single. It appears that only the bottom gasket is leaking and possibly there is a small amount between the filter and the compressor body but that may just be "splash". Either way, I don't need a huge gasket kit - just those two. I have read the -20 now several times so I'm ready to go minus the appropriate gaskets.
Here is a link to a gasket set that may work for you

Single Cylinder
 
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ToddJK

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I've used the sheet type of gasket material, from NAPA. We had to learn how to cut it out and everything in Auto Tech class in school. We had a good teacher. With all the cars and trucks we worked on, it was easier to give a student a piece and make it work, and upon inspection by the teacher before assembly, put it all back together. It was just easier and quicker than ordering separate types of gaskets for various vehicles throughout the day. We did the hammer method, hand trace method, and even just taking a blank piece and sandwiching it between the parts to create the outline. Never thought about using shell casings though for bolt and oil holes, that's a great idea.
 

kenn

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I've used the sheet type of gasket material, from NAPA. We had to learn how to cut it out and everything in Auto Tech class in school. We had a good teacher. With all the cars and trucks we worked on, it was easier to give a student a piece and make it work, and upon inspection by the teacher before assembly, put it all back together. It was just easier and quicker than ordering separate types of gaskets for various vehicles throughout the day. We did the hammer method, hand trace method, and even just taking a blank piece and sandwiching it between the parts to create the outline. Never thought about using shell casings though for bolt and oil holes, that's a great idea.

Thanks again, gentlemen! I have just about every caliber casing from .22 to .50 so I'm sure I've got something the right size.
 

kenn

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For future reference of those that might read this thread, I cannot find the torque values for the nuts that hold the compressor in place. Before I tear the thing off and replace the gasket, I'd like to check the torque. I searched TM9-2320-209-34-1 , 2, and 3 as well as the -20. The 209-34s say:

" TORQUE VALUES. Critical torque values for a particular component are given in the maintenance procedures in chapter 2. When torque values are not given, bolts, screws, and nuts are to be tightened as given in table 1-1. "

So off to table 1-1 I go. There is only one page for table 1-1 and it only contains values for cap screws. The -20 only says to replace the 4 bolts holding the compressor with new washers. OK. What torque? I would have to assume that pretty much every bolt that holds some kind of critical component is at least a grade 5 rather than 1 or 2. If I assumed that (and it's a dangerous assumption), then I'd torque the nut based on the bolt, correct? I don't know the size of the studs yet as I haven't pulled it but assuming it is, say, 3/8" 16 pitch, I would assume torqueing to 31ft lbs would be the number? Obviously I don't want to crack the compressor mounting base nor do I want to pop a stud! I haven't noticed any nut markings on anything I've removed anywhere so far. Perhaps I'm not looking hard enough but without markings on the nuts I don't know the grade.

Thanks!
 

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Mullaney

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For future reference of those that might read this thread, I cannot find the torque values for the nuts that hold the compressor in place. Before I tear the thing off and replace the gasket, I'd like to check the torque. I searched TM9-2320-209-34-1 , 2, and 3 as well as the -20. The 209-34s say:

" TORQUE VALUES. Critical torque values for a particular component are given in the maintenance procedures in chapter 2. When torque values are not given, bolts, screws, and nuts are to be tightened as given in table 1-1. "

So off to table 1-1 I go. There is only one page for table 1-1 and it only contains values for cap screws. The -20 only says to replace the 4 bolts holding the compressor with new washers. OK. What torque? I would have to assume that pretty much every bolt that holds some kind of critical component is at least a grade 5 rather than 1 or 2. If I assumed that (and it's a dangerous assumption), then I'd torque the nut based on the bolt, correct? I don't know the size of the studs yet as I haven't pulled it but assuming it is, say, 3/8" 16 pitch, I would assume torqueing to 31ft lbs would be the number? Obviously I don't want to crack the compressor mounting base nor do I want to pop a stud! I haven't noticed any nut markings on anything I've removed anywhere so far. Perhaps I'm not looking hard enough but without markings on the nuts I don't know the grade.

Thanks!
.
I think if I were you - and with serious lack of hard evidence - I would start out with 20#, then go around the four bolts again at 25#, and then a third round at 35# and call it good. Especially if you have a "nut and bolt" kind of connection. And to be sure, maybe a little lock-tite on those bolts.

If the compressor sits on studs, you need more and better information (IMO).

AND then the key is to check torque after you have warmed up the cast iron.
Maybe even check it again after a week or so...
 
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