Poorman's guide to Vacuum Testing

[Eccentric]

I've been reading this thread for a while now with the intention of getting set up to do pressure/vac testing. I never used to pay too much attention to those who would always reply to any running issue with "pressure and vac test it".

Now I realise this is really good advice and a very simple common sense starting point when working on a saw, especially for those of us who buy them broken, history unknown.

So initially I was thinking that the Mityvac was the way to go, but unfortunately these aren't the most common here in the UK and sellers seem to know this and certainly price the pressure/vac model like they're rocking horse manure.

I didn't want to have two different set ups so I found a new compound gauge with a 4" dial on ebay quite cheap and our friendly maintenance fitter at work supplied the fittings I have up to now.

Not exactly compact but I won't have any trouble reading the dial. I've bought one of those bulb type blood pressure pumps on ebay but this is gonna be a while as it's coming from China, so I should be geared up for pressure. The one thing I haven't yet worked out is what I'm going to use for vacuum.

Any ideas on a cheap vacuum pump anyone? I suppose I could look for a really cheap brake bleeder maybe? When I type in hand vacuum pump on ebay most of what comes up seems to be a pump attached to a clear plastic cylinder with inches marked on the side "From United States", go figure?

I'll post a pick of the finished assembly once I have it all together.

There's gotta be some kind of hand opperated vacuum pump available to you folks in the UK. The Mityvac is what we get here in the States. Must be an equivelant on your side of the water. Go to a UK automotive enthusiast site and see what they're using.........or you could just into your local car repair shop and ask them what they use and where they got it.

 

[captoaklog]

Niiiiiice work....thank you for the time

 

[SkippyKtm]

This is a wee bit off topic but does anyone know what happened to Four Paws? He just kind of vanished back in January of 2009...

 

[kev1n]

That's a nice gauge, I have on similar and would like to buy a new one. Did the seller have more available or was it a one time deal? Mine is a bulb type pump that you just flip around to do vacuum. I'd like to find a new one of those as well, Here is something similar to the one I have.

Kevin
Heathrow Scientific HD20631B Vacuum/Pressure Bulb without Tubing, 85mL Capacity, Rubber:Amazon:Industrial & Scientific

 

[Dan Forsh]

There's gotta be some kind of hand opperated vacuum pump available to you folks in the UK. The Mityvac is what we get here in the States. Must be an equivelant on your side of the water. Go to a UK automotive enthusiast site and see what they're using.........or you could just into your local car repair shop and ask them what they use and where they got it.

I'm not saying I can't buy Mityvac, I could now just buy the basic vacuum model without a gauge (roughly about 45-50 USD), but I'm being kind of pig headed now; I decided to not buy the bells and whistles Mityvac and opted to try to build my own for cheap, so I would feel like I caved if I bought one now (still might though:msp_smile.

That's a nice gauge, I have on similar and would like to buy a new one. Did the seller have more available or was it a one time deal? Mine is a bulb type pump that you just flip around to do vacuum. I'd like to find a new one of those as well, Here is something similar to the one I have.

Kevin
Heathrow Scientific HD20631B Vacuum/Pressure Bulb without Tubing, 85mL Capacity, Rubber:Amazon:Industrial & Scientific

Sorry Kevin, I just checked and the seller doesn't have any other gauges for sale, I think it was a 1 off, new old stock. Thanks for the lead on the bulb pump though, that might be an option if I can source similar over here.

 

[Eccentric]

Wow. We can get the 'bells&whistles' Mityvac for $40 USD or less.

 

[heimannm]

A large syringe from a farm fleet place or animal health supply works pretty well for most jobs and cna create pressure or vacuum depending on where the plunger is when you connect it.

Think large as in horses, cows, or I suppose water buffalo and elephants if you're in Asia some where.

As other have reported, $1.50 each or a three pack for $4 depending on where you find them.

Mark

 

[K5krawler]

Regulator & Gauge

This is my set up which includes a the quick connect at both ends so I can put this inline and have regulated pressure to my small blow gun. The small blow gun works great for fitting into the impulse lines on most saws. I've used it once and it works really nice and once the regulator is set, all I have to do it plug it in and verify that I am at 10 PSI and we are golden.

 

[nstueve]

Just got the MV8500 kit online cause i found it cheap and un-used... Needed one for a while but I'm still not seeing any specific info in this thread about leak/vac limits.

Guessing 6-12psi to pressure test will get the job done and help find leaks... Should the amount of pressure you use depend on the saw or will 6-12psi be good for just about any saw?

Also, is there a bleed rate when you vaccuum check that we should be looking for? A bench mark number to go by? ie: after 1min leak is >4psi you need to find and fix leak?

Another idea for attaching your vac pump to a saw with no impulse line is to get a plastic piston stop. Drill a hole down the length of it. Add a o-ring between the top and the threads to stop air leak. Screw in a brass connector like seen in other photos, to the top of the piston stop (to attach the vac hose). You can also chop the bottom of the stop off to allow the crank to rotate. Cheap and easy way to make a spark plug adaptor. I recommend a drill press for drill the hole down the length of the piston stop.

 

[heimannm]

I just knocked the insulator out of a spark plug and tapped the base for a 1/4" pipe fitting and installed a barbed connector. Works slick.

K5 - you have to disconnect the air supply and make sure it will hold pressure, testing the crankcase for vacuum or pressure has to be static, not dynamic. Your rig would work for a leak down if you included a flow meter, but even a simple one costs about $175.

Mark

 

[arrow13]

Pressure and Vac testing methods

Outstanding info. Thanks everyone. This will undoubtedly help me keep my saws running well. Currently working on an 076 Super with what I believe is an air leak. Got one of the Stihl vac/pressure testers via ebay recently to use for this project, and my other saws.
Will

 

[sawlog1992]

WOW- I wish this could be put somewhere it woul be easy to find

Now I am off to see what "SQUISH" is

 

[Moparmyway]

Now I am off to see what "SQUISH" is

If you dont have the manual to determine the correct bolt torque, then Squish is "when you think its squished enough, squish it a little more" ......................If you have the manual, follow it !

 

[Fish]

Now I am off to see what "SQUISH" is

That is how I got married the first time!

 

[Fish]

That is how I got married the first time!

Well, maybe more.....

 

[PogoInTheWoods]

That is how I got married the first time!

Evidently without the latest torque specs.

 

[president]

kudo's will be on top drawer in the whitehouse secret file drawer

 

[mikerecike]

Where will i find the four paws vac test pdf? Thanks

 

[tntblaster14]

So I'm sorta new to vac testing. Got my 346 sealed up, it will pass pressure but not vacuum. So obviously a leak somewhere. How do you find the vac leak? Smoke? Dunk the whole saw in water (really don't wanna do this one), or something else?

 

[gunnusmc03]

I spray the suspected leak areas with windex and look for bubbles.