Joined: Nov 25, 2007 Posts: 56 Location: Marietta, Georgia
Posted: Mon Dec 10, 2007 7:56 am Post subject: Engine Cylinder Compression Test Gauge
Can someone tell me how to make/build a gauge to test engine cylinder compression? I have an air pressure gauge and some old spark-plugs - was hoping I could use this to rig up something using some cheap plumbing parts from Home Depot.
Barring that, how about the best place to buy such a tool and model number, etc.
Joined: Apr 18, 2005 Posts: 458 Location: Rhode Island
Posted: Mon Dec 10, 2007 8:17 am Post subject: M38 jeep
Hello TDavis,
It looks like you are just starting to work on your jeep and welcome to the list.
The three questions you posted can be answered in short or long but the BEST thing to do is be sure you get the manuals for the jeep. There is a ton of information in them that will help, with pictures, show you how to lift the body, install drivetrain, run compression checks etc. Its good stuff.
The very short answers are:
Buy a compression tester from NAPA or local auto parts store or your favorite low-cost website. I suppose someone has built one but these are relatively inexpensive and I always find that troubleshooting tools is never more productive than using them.
Removing the body. Lots of ways but the book shows how to use straps. You can also use 4 of your friends.
Once it is off you may want to stow it on its side secured to a wall in the garage. I usually use a couple of tires on the floor as a base to sit the side on. They are soft and spread the load a bit so you dont put all the weight on one part of the body.
Axles - these are generally self aligning when installed with correct original springs and hardware.
Great to hear you are digging into the project. Hope this helps.
Joined: Nov 25, 2007 Posts: 56 Location: Marietta, Georgia
Posted: Mon Dec 10, 2007 8:59 am Post subject:
Tom, thanks for the msg.
As far as a library goes …
I have these in both paper and electronic (PDF):
TM 9 – 8014 (Operation and Maintenance)
TM 9 - 8015-1 (Engine and Clutch)
TM 9 - 8015-2 (Powertrain and Body)
ORD 9 SNL G-758 (Full, detailed parts listing)
And these in paper only:
AR 850-5 (Markings)
TB 9 – 2855-43 (Personnel Hot-water Heater Kit Installation)
TM 9 – 2320-208-20P (Repair parts and special tools)
TM 11 – 284 (Radio Sets – AN/GRC-3, -4, -5, -6, -7, and -
I also have all revisions/updates to the above, if there are any.
I’ve asked for this for Christmas … http://www.vintagevideo.com/jeep/index.html - shows a rebuild of a WWII Jeep, but I hoped to learn something out of it and get motivated.
Joined: Apr 18, 2005 Posts: 458 Location: Rhode Island
Posted: Mon Dec 10, 2007 9:21 am Post subject:
Fantastic,
Those are the manuals and your library is much more complete than mine.
I also have spent many hours pouring through books, reading and re-reading sections. Great stuff.
I'll let you know how the hoist method of body lift works. The sheetmetal work on my M38 tub is done and I'll test fit it to the frame sometime in the next two weeks. Usually I just have a few people over to lift the tub on or off but after the test fit, I'll be removing the tub again until I can paint it in the spring.
Is your A1 running? You mentioned engine rebuilds but what is bring you to think it needs a rebuild? As a very rough guide, I spent about $1500 having my M38 machined and reassembled. It needed to be bored, crank turned, valve guides, I chose hardened exhaust valves and seats, clean/true the head, new pistons, bearings, oil pump etc etc etc. It can be done less expensively and more expensively. Be sure your machine shop is interested in doing these old engines.
You can do the trans and transfer yourself. There are a couple of great websites. I also got a $5 T-90 video at one of the MV meets. Your wife will love that one.
Looks like you are thinking of a cylinder leak down checker if you are considering using a compressor.
The compression gage simply screws in the plug hole and reads pressure in the cylinder when the engine is cranked over.
A leak down tester is used to more accurately determine exactly what may be causing a low compression reading. This tool has a pair of air pressure gages connected with a calibrated orifice (usually .040) between them. You connect your air compressor to one side and then connect the other side to the cylinder you are testing. Then with the cylinder's piston at TDC you pressurize the cylinder using an inlet pressure of 80 PSI. Your outlet pressure should fall between 50 and 80 PSI. A dynamic seal (the seal between the rings and the bore also known as the moving seal)leak down figure of about 60 on all four cylinders with the low cylinder within 10% of the high cylinder is ok. Static seal ( leakage thru valves, gaskets and block cracks) should be Zero. You can listen for valve leaks at the exhaust pipe and the intake manifold/carb. Head gaskets leaks can be heard whistling into the adjacent cylinder or via bubbles in the radiator.
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