Mytyvac pump help

[Jeffrey S.]

While using my Mytyvac yesterday I noticed that it would not hold the vacuum after pumping up while attached to a known good diaphram. It slowly bled off. Is this normal? If not, does anyone have a link to a video showing a rebuild? As always, thanks for your help.
Jeff

[Dan A.]

Re: Mytyvac pump help

Jeff, some years ago I bought a rebuild kit from Eastwoods. If I remember correctly instructions came with it.

Dan

[Keith B.]

Re: Mytyvac pump help

it should hold the vacuum for a few minutes.

[Paul D.]

Re: Mytyvac pump help

Jeff, just to be clear, does it do the same thing when you hold your finger over the end of the hose or port on the pump? The reason I ask, I once called a choke pull-off bad for not holding vacuum and was surprised to find out that the new one did the same thing. When I took it back to the FLAPS I was schooled on how that particular pull-off was designed for a slight bleed of vacuum. Chip.

[Jeffrey S.]

Re: Mytyvac pump help

Paul,
In fact when I put my finger over the port it won't pull any vacuum at all. When installed on a vacuum diaphragm, in this case a FI part, it draws a vacuum activating the part but slowly bleeds off. I guess I should try this on a known good VAC and see what happens.
Jeff

[Edward B.]

Re: Mytyvac pump help

In fact when I put my finger over the port it won't pull any vacuum at all.

That just doesn't make any sense if the unit is working.

[John D.]

Re: Mytyvac pump help

Jeff, Best thing to do is buy a new Mityvac pump. Today they are made in China. But let me tell the part is very high quality. Weighs a ton and holds vacuum perfect.
The old plastic Mityvacs weren't too good. The cast ones were better. But none compared to this Chinese one. Seriously. JD

[Jeffrey S.]

Re: Mytyvac pump help

That just doesn't make any sense if the unit is working.

I agree and that is why I would consider rebuilding.

John,
It is the all metal unit purchased about 15 years ago. It probably would cost as much to buy the parts as it would to get a new unit. Thanks for your responses.
Jeff

[David J.]

Re: Mytyvac pump help

While using my Mytyvac yesterday I noticed that it would not hold the vacuum after pumping up while attached to a known good diaphram. It slowly bled off. Is this normal?
Jeff

I feel your pain on this issue. I have 2 metal and 4 plastic bodied Mityvac pumps. I have just about given up on keeping any of them vacuum tight. I've found the most common offending component inside them is the seal diaphram at the bottom of the pump chamber if that makes any sense. It is almost impossible to remove and clean/lube, so I have resorted to using a small plastic model size paint brush to get lube under the seal and between it and the bottom of the chamber. I use silicone grease to prevent any interaction between the diaphram and petroleum products. The fix is only temporary in most cases however. I have had much better success with the plastic bodied Mityvacs, however I do break handles on them every so often.

What I have resorted to is to continue to use a Mityvac to evecuate atmosphere from the component or circuit I am testing, however I have added another component. I use a "T" connection in the middle of three vacuum hoses. One hose to the Mityvac, second hose to a standard vacuum gauge tested vacuum tight, and the third hose to the component or circuit to be tested. Once the triple circuit is Mityvac'd, I use a needle nose vise grip pliers to close or pinch the hose leading to the Mityvac. This insures me that what I am testing is indeed vacuum tight, or leaks. Simple......

When I test the entire vacuum circuit on a C3, I use the same set up, but I substitute a medical aspirator in place of the Mityvac.

I probably perform hundreds of vacuum tests per year. Wiper arm safety valves, headlight switches, relays and actuators, all C3 related.

[John D.]

Re: Mytyvac pump help

One thing I really don't like about the foreign made mityvac is it weighs a ton. But the workmanship is 1st class. If you can rebuild your old one with a kit then go for it.

[Jeffrey S.]

Re: Mytyvac pump help

David,
Thanks for your comments and suggestions. As a simple hobbyist, not a professional, your solution may be a bit of an overkill. If I did as many tests on vacuum systems as you do it would be very important to be as accurate as possible. That being said I will consider using your suggestions. For me, just checking to see if a component like a VAC or actuator is functioning is good enough for now. I really appreciate you taking the time to detail a well thought out solution for me.
Jeff

[Jeffrey S.]

Re: Mytyvac pump help

John,
Thanks again for your comments. After I check the pump on a known good VAC I will decide how to proceed.
Jeff

[Mark E.]

Re: Mytyvac pump help

When I test the entire vacuum circuit on a C3, I use the same set up, but I substitute a medical aspirator in place of the Mityvac.

Thanks for your insight, David.

Would you say more about using an aspirator to evacuate a vacuum system? This seems clever; is it like having a powered MityVac? Can you recommend an inexpensive one that works for this purpose?

[David J.]

Re: Mytyvac pump help

Hello Mark,

These aspirators are somewhat similar to A/C vacuum pumps, only they have a much lower volume and pressure attributes. Perfect for imitating the vacuum in a running engine, only with no danger of excessive vacuum to pop seals and such. My aspirator was made by Medical Industries America, and the model # is 905CA18. This number seems to be somewhat common in the medical industry, as other makers use it also. I did not pay much for mine years ago, and found it on ebay. Pic below.

Using it is pretty simple. Just connect it to the single port side of the check valve and let'er rip. It takes about a minute or two to power up the entire system if everything is tight, and mine will pump to about 20 lbs or so. I also put a regular vacuum gauge in line off a "T" connection to keep tabs on pressure. It also has a bleeder valve to act as a regulator of sorts if needed. Yes, you could say it's like a powered Mityvac!

There are several right now on ebay. I could send you a PM link if you like on 2 from $25 - $50 before freight. Let me know.

I will be in the Dallas area in late October or early November if any one would like to have a free tech session on C3's vacuum systems. My mother lives in Allen.

[Mark E.]

Re: Mytyvac pump help

...mine will pump to about 20 lbs or so.

I will be in the Dallas area in late October or early November if any one would like to have a free tech session on C3's vacuum systems. My mother lives in Allen.

Thanks David!

I assume you mean 20" of vacuum?

Are you in town for the Frisco Regional (near Allen) in October? I'm interested in a vacuum system tech session, and others may also be interested. Maybe that can be worked out.