Vacuum gauges were an option to have installed with the dashboard innstruments. It helped to save gas by teaching the driver to have a lighter touch on the gas pedal by trying to keep the pointer in the green (higher vacuum). The movement of the pointer also indicated the condition of the engine while driving. Stuff like carb imbalance, burnt valves, worn valve train, worn rings, vacuum leaks, etc. I used a vacuum gauge when adjusting points dwell and idle mixture when tuning up engines.
100%, its the most powerful yet underutilized tool! I have used a vacuum gauge to find many of those hard to find issues. Plus if you can't use a vacuum gauge then how can you use a delta sensor with a scope to monitor vacuum? I agree vacuum gauges need more use guys!
@@MasterAutomotiveTraining The issue with vacuum gauges is that you cannot reliably diagnose Atkinson cycle engines as they do not have much of any steady intake vacuum (as they actually push air out from the cylinder in part of the compression stroke, which nullifies manifold vacuum). If you use a vacuum gauge on an Atkinson cycle engine, then it will read near zero at all times. This is the reason why Toyota uses separate vacuum pumps to supply vacuum for most of their engines in the last 10-15 years. It is also why they don't have any testing procedure that involves testing for vacuum for nearly anything engine related. So right off the bat that one of the US' largest car manufacturers where you can't use vacuum gauges for diagnosis. They're great, but they have some severe limitations.
I learned a lot from this one! Do a part 2 where you do the same vacuum tests but they fail and you tell us what to look for as possible causes. Thanks
Very nicely done, I have been using vacuum gauge professionally since 1989 and all these kids just look at me like I'm insane. But my diag time is better than there's.............🤦
2:28 Engine idle vacuum test (18-22 inches at sea level -1 inch for each 1,000 ft of elevation) 4:30 low power when you accelerate fast - perform snap test to see if restricted exhaust, (snap throttle and vaccum should drop to zero and then stabilize back to normal) 6:08 Cranking no start - perform cranking vacuum test to see if there is a problem with the valvetrain or timing belt/chain (3-5 inches)
Great video and explanation...but you can use the metal pipe at the brake vacuum booster, as long its towards the intake manifold. A small distance away you are at the intake manifold. Great video.
Great information. My 289 is running at idle only 8 inches of vacuum. I will try your cranking test. I was hoping the problem was the intake manifold and not the valves
nice video, I've been enjoying these so far. I'd like to hear your explanation for the "why's"... during snap test, why does vacuum go to zero on a healthy engine, but actually climbs if the exhaust is restricted.
At wide open snap throttle the butterfly valve at the throttle body is completely opened up to atmospheric air …. therefore, no difference in pressure exists - in other words; no vacuum can be created .
Love this quality content! Was wondering how i could tap into my 91 chevys system to test vaccum. I got a 5.7l v8 TBI and dont know where id connect a vacumm gauge at...
Excellent Job. Clearly taught for understanding. Will be looking at your other videos also. Again you did a great job. However I would like to see videos on more Classic cars like my 76 Corvette. SMILE- Thanks
Hooked up a gauge to my 350 sbc needle goes to the timing in red just before the green for normal engine. Checked the timing is at 8 degrees before tdc. Starts up fine . Why wont it go into the green for vacuum check .Thank you much . Ruben
@@rubenosuna115 Gotcha. Just with the 3200 elevation that would drop vacuum to 15-18" being at 15" would be perfect, especially with the engine mods and carburetor.
great video- I followed the rabbit hole here from the affect valve lash has on vacuum--would be great to see a video on valve lash and how to do it properly
Hola Oscar,muy agradecido por tan informativo video, pregunto,por casualidad haces también en español?Pues mi inglés no es tan bueno.Muy pero muy agradecido.Bendiciones.
Thank you for pointing out exactly where to hook the line. So many videos simply say, "Hook it to your vacuum." Which is not helpful at all for those who don't know.
Can loss of engine compression effect the brakes. The following dashboard lights stay on. Check trailer brake system, check brakes, traction control off, stabil-trac off and cruise control don't work. I've replaced everything except the brake booster and master cylinder.
Yes, since low compression creates less vacuum, will create less negative pressure on the front of your brake booster leading to lessened brake effect. Do you feel any braking problem?
My brake caliper cylinder stuck even new caliper. I change brake vaccum hose but still caliper cylinder stuck & brake Rotor get hot. Is any body know what will be problem.
@HappySailor2000 i had the rubber seals/washers on my brake caliper slide pins swell up, which prevented the calipers from releasing. I removed them and all is well again.
Great video oscar I just you in youtube today,and I like lt very much, I suscribed also to your channel, thank you and cheers from Ontario ca, I will keep watching tus videos, later
That's a great question Bob. If your car has a MAP sensor the reading you see is the difference in pressure from atmospheric to intake. Minus the reading your MAP sensor gives to the BARO reading on your cell phones weather app, the difference is the engine vacuum. Example: MAP reads 17hg and your BARO says 29.9hg. Your engine vacuum would be 12.9hg" did that make sense?
Thank you for these beautiful solutions. What about if you want to buy a car, and check it through the computer, especially since the car contains an internal computer that carries all the faults with codes, stores them, and displays them in case of examination
It's a good idea. However the codes might have been cleared by the seller just before you scanned it, so your Check Engine Light will be off. And then the light may come on on your way home.
Thank you for the detailed explanations. Is Vacuum Gauge Test better than Smoke Machine Test? How do they compare on small and large leaks? Do you have any films on Smoke Machine Testing. I need to learn better where exactly to connect the hose w/smoke for different tests. Thank you again, really good film.
Great video, a suggestion is use the vac gauge and show how to troubleshoot the PCV System. The most unchecked and misunderstood system under the hood.
This is excellent information! I really appreciate it. Question, is the vacuum test on a running engine, if it shows an acceptable inches of mercury range and the needle is not shaking, is that definitive enough to say the internals of the engine are relatively healthy? Would that be so reliable that I wouldn't even have to do a compression test?
![Short Term and Long Term Fuel Trims Explained [Easily]](http://i.ytimg.com/vi/IuM53mlOgHs/mqdefault.jpg)
Vacuum gauges were an option to have installed with the dashboard innstruments. It helped to save gas by teaching the driver to have a lighter touch on the gas pedal by trying to keep the pointer in the green (higher vacuum). The movement of the pointer also indicated the condition of the engine while driving. Stuff like carb imbalance, burnt valves, worn valve train, worn rings, vacuum leaks, etc. I used a vacuum gauge when adjusting points dwell and idle mixture when tuning up engines.
Yes, I recall seeing them when I used to work on old carbureted vehicles in my earl days as a technician.
The vacuum gauge is the most under used diagnostic tool and its filled with overlooked valuable information. Agree?
100%, its the most powerful yet underutilized tool! I have used a vacuum gauge to find many of those hard to find issues. Plus if you can't use a vacuum gauge then how can you use a delta sensor with a scope to monitor vacuum? I agree vacuum gauges need more use guys!
@@MasterAutomotiveTraining The issue with vacuum gauges is that you cannot reliably diagnose Atkinson cycle engines as they do not have much of any steady intake vacuum (as they actually push air out from the cylinder in part of the compression stroke, which nullifies manifold vacuum). If you use a vacuum gauge on an Atkinson cycle engine, then it will read near zero at all times. This is the reason why Toyota uses separate vacuum pumps to supply vacuum for most of their engines in the last 10-15 years. It is also why they don't have any testing procedure that involves testing for vacuum for nearly anything engine related.
So right off the bat that one of the US' largest car manufacturers where you can't use vacuum gauges for diagnosis. They're great, but they have some severe limitations.
That, and using a smoke machine to find leaks (Exhaust, intake, etc)
@@LordOfSilense
Would it be good to use on Saturn engines? I have a Saturn Ion-2 2.2 and think i might have a vacuum leak
That's so true! I can't find the issue with my 289cui and now iam hoping to get it diagnosed with the vacuum gauge!
I learned a lot from this one!
Do a part 2 where you do the same vacuum tests but they fail and you tell us what to look for as possible causes. Thanks
Thank you very informative and I always use a vacuum gauge on a carburetor guy myself. I have a 67 CJ five and a 56 Chevy four-door station wagon
This is the most informative video I've seen on how to use a vacuum gauge. Thanks
Great presentation, verbally excellent, no pauses. Amazing 🤙🏼
Great presentation, great diagnostic method, well done!
Thank you!
Awesome clear and to the point, best video on vacuum gauge.
Very nicely done, I have been using vacuum gauge professionally since 1989 and all these kids just look at me like I'm insane. But my diag time is better than there's.............🤦
Great session. Thanks.😊
You're welcome 😊 Glad you enjoyed it!
2:28 Engine idle vacuum test (18-22 inches at sea level -1 inch for each 1,000 ft of elevation)
4:30 low power when you accelerate fast - perform snap test to see if restricted exhaust, (snap throttle and vaccum should drop to zero and then stabilize back to normal)
6:08 Cranking no start - perform cranking vacuum test to see if there is a problem with the valvetrain or timing belt/chain (3-5 inches)
Awesome video learned alit in the short period of time thanks
Thanks for sharing your knowledge ! Very useful in refreshing my mind as a mechanic of unused knowledge.
This is a good video. I would like to know more about vaccum testing setups ( Connections to the car).
Great suggestion! Coming soon!
Fantastic video. Huge thanks my friend.
No matter how much you know, the matter is how to teach someone about what you know, you really very good teacher
Great Session. Very helpful.
Glad it was helpful!
Excellent presentation and very informative! Thank you!
Thank you
Great video and explanation...but you can use the metal pipe at the brake vacuum booster, as long its towards the intake manifold. A small distance away you are at the intake manifold. Great video.
Great explanation
It’d be highly appreciated if you make a video about fuel trims
Great information. My 289 is running at idle only 8 inches of vacuum. I will try your cranking test. I was hoping the problem was the intake manifold and not the valves
nice video, I've been enjoying these so far. I'd like to hear your explanation for the "why's"... during snap test, why does vacuum go to zero on a healthy engine, but actually climbs if the exhaust is restricted.
At wide open snap throttle the butterfly valve at the throttle body is completely opened up to atmospheric air …. therefore, no difference in pressure exists - in other words; no vacuum can be created .
Very good presentation brother.
Many many thanks
Love this quality content! Was wondering how i could tap into my 91 chevys system to test vaccum. I got a 5.7l v8 TBI and dont know where id connect a vacumm gauge at...
I installed a vacuum gauge in the dash of my '88 Chevy G30. I teed off the vacuum line going to the vacuum accumulator.
Superbly informative. Thank you very much...
You are welcome, thank you for watching.
Excellent Job. Clearly taught for understanding. Will be looking at your other videos also. Again you did a great job. However I would like to see videos on more Classic cars like my 76 Corvette. SMILE- Thanks
Hooked up a gauge to my 350 sbc needle goes to the timing in red just before the green for normal engine. Checked the timing is at 8 degrees before tdc. Starts up fine . Why wont it go into the green for vacuum check .Thank you much . Ruben
Any modifications to the engine? By red you mean 10"hg or less? Or in the 15"hg mark?
Yes had light modifications done. Needle is in the 15 hg red
@@rubenosuna115 Were the mods a cam? Is it carbureted? 15hg isn't bad, also what is your altitude?
Yes isky cam flat top piston , 600 edelbrock, and performer Rpm intake. Only about 3200 for elevation.
@@rubenosuna115 Gotcha. Just with the 3200 elevation that would drop vacuum to 15-18" being at 15" would be perfect, especially with the engine mods and carburetor.
Another great video. Thnx again Oscar. 😊
great video- I followed the rabbit hole here from the affect valve lash has on vacuum--would be great to see a video on valve lash and how to do it properly
thank you so mush for this helpful information
You are so welcome! Glad it helped.
Thank you, very useful information explained very well.
Glad it was helpful! 😁
You ask for a comment to be better, sadly this video is just perfect.
Thank you for those kind words!
As a DIY guy that's just bought a scanner I realise now how much things have changed after 30years, thanks for posting i will be watching all the vids
Awesome video. I'm 71, in our days all of us gear heads used this gage. Great job
Thank you, my mentor showed me the power of it and I still use it to this day.
Thanks for showing where to test and how much vacuum to see and at what elevation........
Great video 🎉
Thank you 😁
Hola Oscar,muy agradecido por tan informativo video, pregunto,por casualidad haces también en español?Pues mi inglés no es tan bueno.Muy pero muy agradecido.Bendiciones.
great video Oscar, how about a fuel pressure video
Muy buenos en video profe Oscar se sigue uno refrescando la memoria con este tipo de informacion
Great information. Thanks Oscar 👍
Thank you for pointing out exactly where to hook the line. So many videos simply say, "Hook it to your vacuum." Which is not helpful at all for those who don't know.
Can loss of engine compression effect the brakes. The following dashboard lights stay on. Check trailer brake system, check brakes, traction control off, stabil-trac off and cruise control don't work. I've replaced everything except the brake booster and master cylinder.
Yes, since low compression creates less vacuum, will create less negative pressure on the front of your brake booster leading to lessened brake effect. Do you feel any braking problem?
My brake caliper cylinder stuck even new caliper. I change brake vaccum hose but still caliper cylinder stuck & brake Rotor get hot.
Is any body know what will be problem.
@HappySailor2000 i had the rubber seals/washers on my brake caliper slide pins swell up, which prevented the calipers from releasing. I removed them and all is well again.
Idk if you figured this out but that happened on my gmc sierra and it was actually the wiring harness rubbing on the frame
Brake line collapsed @@HappySailor2000
Te has ganado un suscriptor más.
Very informative. Very professional. Just a tech trying to get better, thank you
Great video Oscar!
Excellent lesson ! You are an excellent coach !!
Your videos are amazing.
Thank you! Thank you for your support!
Do you have any videos for the A1 test? I learn a lot from your videos. Thank you for posting them.
What is best cheap fuel pressure tester ?
Great video oscar I just you in youtube today,and I like lt very much, I suscribed also to your channel, thank you and cheers from Ontario ca, I will keep watching tus videos, later
Perfect explanation 👏💙
Great job good info and simple . I like simple
What would be the reading if there is head gasket failure ?
Excellent i want to learn more👏👏🤗🤗
Great explanation well done
You are not just a mechanic but instructor
A Technician
Great video.👏👏
really enjoyed it, never thought to use it on car purchasing. also on newer cars with obd-2 scanner will the readings on that work the same?
thank you very much very helpful and easy method
are VAC READINGS accurate on a scan tool thx bob
That's a great question Bob. If your car has a MAP sensor the reading you see is the difference in pressure from atmospheric to intake. Minus the reading your MAP sensor gives to the BARO reading on your cell phones weather app, the difference is the engine vacuum.
Example: MAP reads 17hg and your BARO says 29.9hg. Your engine vacuum would be 12.9hg" did that make sense?
@@MasterAutomotiveTraining ok thx!
@@MasterAutomotiveTraining i do have a VAC gauge next time I'll check both ways an see what i get for readings.
TY VERY MUCH. VERY KIND AND INFORMATIVE.
What fuse you remove it
Fuel pump fuse. 😁
Love it. Well done
Great video bro and thank you🙏 Does it matter which hose you pulled off the purge valve I noticed there were two ports/
Thank you for watching, use the hose from the solenoid to the intake manifold to run the vacuum test.
Am from Kenya and that an easy explanation for one to understand 👍
Thanks for share
My pleasure.
Talent mechanic
This is a great video. Very useful. I am working 2003 Honda civic AKA Honda Accura 1.7 L. What is the best place to hook up the gauge?
Thanks Bud !
Good video thanks
Nice tutorial I’m in👍👍
Ronnie from belgium 👍
Wow very good informative video.
The selanoid valve has two hoses
Which one you use for the test? Thanks
where is the download link in the description?
drive.google.com/file/d/1cjP8svFw_cq6EmSDaJe_MwbyWIfwr3C1/view?usp=sharing
8:15 @@MasterAutomotiveTraining8:15
worksheet link?
drive.google.com/file/d/1cjP8svFw_cq6EmSDaJe_MwbyWIfwr3C1/view?usp=sharing
What is a restricted exhaust by any chance if u don't mind me asking
How about the vacuum test on a turbo charger engine is there any way to check to vacuum ?
Thank you for these beautiful solutions. What about if you want to buy a car, and check it through the computer, especially since the car contains an internal computer that carries all the faults with codes, stores them, and displays them in case of examination
It's a good idea. However the codes might have been cleared by the seller just before you scanned it, so your Check Engine Light will be off. And then the light may come on on your way home.
Thank you for the detailed explanations. Is Vacuum Gauge Test better than Smoke Machine Test? How do they compare on small and large leaks? Do you have any films on Smoke Machine Testing. I need to learn better where exactly to connect the hose w/smoke for different tests. Thank you again, really good film.
Hi what is proper vacuum for single cylinder engine
Great video!!!!!!!
outstanding!
good vedio
Should I increase idle rpm a little bit and ignition advance to increase vacuum pressure if its at 45cmhg?
45cm hg is equal to 17 hg” no need to rev it, you are within proper spec.
Hi Sir. Tell me please petrol engine and diesel engine have the same reading. Thank you.
Is it normal to be low if I do the test with the ac on because I had the ac on and it was low but with out the ac on it was on the right pressure
Yes, as the AC compressor adds load to the engine, which reduces the engine vacuum.
What if the vacuum gauge is erratic and also reading low? It's a 2008 Buick Lucerne
I read your question, does the Lucerne also have a drivability concern? Mil? DTCs?
Great video!
Can we use vacuum gauge to set idle mixture?
just a quick qustion,would this test work on a diesel engine(or certain diesel engines)
I have a ford escape v6 2012, I can't find the vacuum line where to hook it up
🤘🤘nice work
Great video, a suggestion is use the vac gauge and show how to troubleshoot the PCV System. The most unchecked and misunderstood system under the hood.
Hi does this test work on turbo charged engines and cars with VVT systems.cheers.
Damn bro thank you for share that knowledge 👌🏼
Dose the fuel pressure regulator’s vacuum go to 0 when you are at full throttle
This is excellent information! I really appreciate it. Question, is the vacuum test on a running engine, if it shows an acceptable inches of mercury range and the needle is not shaking, is that definitive enough to say the internals of the engine are relatively healthy? Would that be so reliable that I wouldn't even have to do a compression test?
Nice good video thanks
Can we see the vacuum tests with bad engines. Is that possible? One with burnt valves. Outta time , exhaust restriction etc
what would a boucing needle indicate on a vacuum test