Crankcase Pressure Testing

Tanner Instructor South Carolina Posted   Latest  

I recently saw a post showing the use of a manometer being used for crankcase pressure testing. I have seen several different ways through the years of doing this Including some that use a scope.

what is your preferred tool to use for this? Also how are you going about doing your tests step by step. Where are you finding your information for what is an acceptable amount? 

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Keith Instructor
Oklahoma
Keith Default
 

I use a MAP sensor with a custom made 5 vdc steady power supply that houses the BNC port for connection to a scope. I have built custom Pico Probe files so I can view the measurement in mBar, PSI, and inHg... Along with the kit is a variation of PCV and oil cap adapters I have made to attach it to a variety of vehicles.

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Chris Diagnostician
New York
Chris Default
 

Funny you should ask Tanner. Amazon sells a really inexpensive digital manometer. This manometer is cheap, portable and accurate. As for a spec, from what I've seen, a good rule of thumb spec is 4-7 inches of water. This is why a manometer is important because your regular vacuum gauge isn't accurate that low as you can see here. and here *images courtesy of amazon and Alldata

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Joel Technician
Maine
Joel Default
 

Buying a digital manometer has been on my to-do-list form 6 months but I wasn't sure which one to buy. Thank you for this post. I just ordered one from Amazon.

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Brady Owner/Technician
Washington
Brady Default
 

I use a magnehelic gauge for testing crankcase pressure in inches of water column. I've been doing it that way for years and I couldn't say for sure why I settled on that unit of measurement. As far as what is acceptable, I take known good readings and record them. Most vehicle's fall between 2-8 inches of water column in my experience. I also use my homeamde "first look" style sensor and pico

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Luke Instructor
California
Luke Default
   

I use a handheld digital manometer similar to what Chris Martino showed. The particular model I use is the 478a made by Dwyer. I like this one because it has a range of -60in to +60in water. It also has some neat features like a min max recorder and the ability to switch between measurement units. I made a simple adapter for quick measurements by drilling a hole in a new oil cap and glueing a

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Ray Diagnostician
Ontario
Ray Default
 

The first waveform is from an 07 Corolla. I have a WPS500 pressure transducer on the dipstick tube at idle to measure the blow by pressures and the pcv vacuum for each cylinder in the crankcase. The crankcase pressures for each cylinder measures positive 7 inches of water column. The pcv vacuum for each cylinder in the crankcase measures negative 4.8 inches of water column. The second wave

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Ronny Owner
California
Ronny Default
 

We use Magna with modified oil cap adapter.

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Mario Diagnostician
Florida
Mario Default
 

Ray, I take it you created a template for this to show up as inches of water? Had no idea the wps 500 was THIS sensitive!

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Matthew Mobile Technician
Illinois
Matthew Default
 

Range 3 is accurate to 5% of scale -5 to 5 PSI (working from memory, could be wrong). Plenty accurate for sensitive tests.

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Michael Diagnostician
Illinois
Michael Default
 

Mario it should be in your range settings for when you select the wps.

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Ray Diagnostician
Ontario
Ray Default
 

Hi Mario, In Autonerdz, Tom Roberts made some Custom Probes for the WPS500. One is for the "in H20" or inches of water column (Range 3), for Evap and pcv and another "inHg" or inches of vacuum (Range 2) for engine vacuum.

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Michael Diagnostician
Illinois
Michael Default
 

Oh Tom made those, oops. Didn't think about that because those settings were always there when I purchased my first scope from Tom. Tom and the crew did a great job making the custom probes for all the accessories. Sorry Mario didn't mean to give the wrong info. I have just been used to having them all this time. WIsh I could help you with this Mario but these probes Tom made are for Picogroup…

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Ray Diagnostician
Ontario
Ray Default
 

The wave forms that I posted are from a 2014 Hyundai Elantra 2.0

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Mario Diagnostician
Florida
Mario Default
 

Awesome, guess I'll know the first thing I'll be doing when i get to work :) should be pretty easy to come up with this custom probe. Thanks fellas!

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Matthew Owner/Technician
Illinois
Matthew Default
   

Hi Tanner, I hope all is well! I use my favorite tool, the Pico WPS 500. I test crankcase pressure for two reasons: - Testing excessive engine blow-by (usually diesel trucks) - Finding the reason for low compression (my experience here is with gas engines). To test diesel blow-by an orifice is usually required. Since most heavy truck engines simply have a filter system excessive blow-by

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Ben Technical Support Specialist
United Kingdom
Ben Default
   

Hi Matthew, Great work on the above and it comes just as I'm looking at more HD work. I have an odd capture and I wonder if you could take a look? We know that there excessive crankcase pressure as the vent puffing away as much as the exhaust!! I wish I had put WPS500 on the crankcase breather as you have done above as I believe this would have made all the difference! My question is though

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Matthew Mobile Technician
Illinois
Matthew Default
 

I have seen it, I guess it is fairly normal. Never given it much thought why, but looks normal to me.

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Ben Technical Support Specialist
United Kingdom
Ben Default
 

Thanks Matthew, Just an odd one as I've never seen it. The first capture I did with the engine a little colder, it wasn't there as frequently but as the engine warmed up it become every other. I believe the engine is being stripped now so will feedback once I know more Thank again Ben

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Michael Diagnostician
Illinois
Michael Default
 

Reason I recommend this Ben is because if you have something wrong with the flywheel it could effect the Starter Current or it could be the starter itself causing a issue. If you have the pressure sensors tapped in you will see a better result. Even though if the starter sounds ok it could be starting to fail. Just a thought. Let me know what you find.

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Michael Diagnostician
Illinois
Michael Default
 

Hi Ben how about next time when you do this type of testing, put a wps in the intake, exhaust, and crankcase. Then use a injector with synch and then your starter current. You can do this all at the same time now that you guys released a 8 channel automotive scope, hooray! I'm going to be getting one hopefully soon.

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Darren Mechanic
Wisconsin
Darren Default
 

Picoscope for sure with pico pressure sensor, checking blowby cylinder by cylinder using a sync of course, usually no. 1 ignition.

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