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sicminds
GenIII
4/20/2005
13:01:02
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 Subject: how to do a compression check
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Could and one give me some tips on how to preform this? Thanks
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Dan
Dodge Dakota
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4/20/2005
13:29:22
| RE: how to do a compression check
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If you are checking cylinder compression then you have to find out what the compression should be or what you want it to be, and then get a compression gauge, it will screw directly into your spark plug hole. Make sure you get one that can go deep into the hole, I know my 4.7 spark plugs are deeply recessed. Then you have to disable the engine. If you have a single coil then take off the coil wire or disconnect all of the wires on the coil packs. Then turn over the engine a few times. The gauge should read the highest compression the cylinder puts out, and then reset the gauge and go to the next cylinder.
Dan
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sicminds
GenIII
4/20/2005
14:06:59
| RE: how to do a compression check
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thanks, any idea on what the compression should be in a 99 5.2l or where i could find it.
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Dan
Dodge Dakota
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4/20/2005
20:00:03
| RE: how to do a compression check
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I looked around a little, but all I found was an article about a 5.2 that was running 130-160 psi, and I am not whether that is normal or not. If I were you I would go out and buy a repair manual, like the ones you get at autozone and such, it should be in there. You can also cheat a little. Do a compression check on all 8 cylinders and record them. A. If you have 1 cylinder that is lower than the rest then squirt some oil in the cylinder and try again, if it gets better you probably have some bad rings. If not then you probably have a bad haed gasket or you have some burnt valves or the worst would be a hole in your piston (but that would make your compression next to zero). B. If you have 2 low cylinders and they are next to each other then bet on a bad head gasket. C. if you have one that is super high then you probably have carbon build up and will need to clean that carbon out of there (probably taking off the head) D. If the compression varies greatly between cylinders, then it is probably time to send it to the shop, unless you are a mechanic, know one that is willing to help you tear it down, or are like me and think no job is too great and start tearing down the engine.
Now I am not a mechanic by any means, and a lot of this I took from a Haynes book so get on with your bad self and keep me informed. Either way, if you decide that you are going to tear the engine all apart, and can get a hoist/cherrypicker, then you might consider pulling the egine, makes it easier to work on a lot of the time.
D
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Kaderdak
GenIII
4/20/2005
22:31:40
| RE: how to do a compression check
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The above post was pretty much right on. Take out all your spark plugs and make sure you disable the distributor in some way or another. Be sure to get the guage screwed all the way into the spark plug port to insure a good seal. Turn the engine over 4-5 times or until the needle quits rising on the guage. I just did a check of all the cylinders on my '97 5.2, got basically 150 on all of them, +/- about 5, which is well within a normal range. Good luck.
** '97 Dakota 5.2L 4x4 w/3.55(my best ebay purchase yet) **
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** Tons more once I'm not a poor college student :) **
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jay
Dodge Dakota
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4/21/2005
13:26:32
| RE: how to do a compression check
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yup 150psi is about where you should be. also, if you have serious carbon build up, trickle (very slowly) some transmission fluid in to the intake. sounds wacky, but im serious. i had a chevy 305 that could not have had any more carbon buildup in it. it has so much, that it kept running after i turned off the keys(with a dieseling sound), cause the carbon actually worked like a glowplug. i dumped tranny fluid inthe the carb, and it blew the carbon out the exhaust. you will get a cloud the size of a house or maybe the size of a small neighborhood, but it works.lol
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daddio
Dodge Dakota
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4/21/2005
13:43:29
| RE: how to do a compression check
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you can do the same with water. just a "trickle" and work the throttle to keep the engine from stalling.
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jay
Dodge Dakota
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4/21/2005
15:07:48
| RE: how to do a compression check
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i dont recommend that. the engine can hydrolock and snap a rod. transmission fluid works good.
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TexasTodd
Dodge Dakota
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4/21/2005
15:14:57
| RE: how to do a compression check
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A fluid is a fluid. Albeit different boiling points.
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jay
Dodge Dakota
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4/21/2005
15:23:27
| RE: how to do a compression check
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tranny fluid burns off.
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daddio
Dodge Dakota
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4/21/2005
15:36:04
| RE: how to do a compression check
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they are both fluids which are NOT compressible. pour enough of either in a running engine is asking for trouble.
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Sneezer
Dodge Dakota
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4/22/2005
09:28:11
| RE: how to do a compression check
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Just use Seafoam. Supposed to do wonders on buildup like that. Huge amount of smoke though.
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Towelie
Dodge Dakota
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4/25/2005
02:19:59
| RE: how to do a compression check
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Don't forget to pin your throttle body wide open.
Also if you have a low cylinder squirt a little 1/4 OZ of oil into the plug hole, if the compression comes up it's likely bad rings. If it does'nt come up it's likely vaves or gaskets.
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Or
Dodge Dakota
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4/25/2005
09:28:12
|  RE: how to do a compression check
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Use could just use a leakdown tester. Similar to compression gauge but uses compressed air and two gauges. Gives you a percentage for what's getting out of the cyl., past the rings, the valves, head gasket. Will enable you to listen for leaking air and be able to determine where it's coming from.
This is a much better method.
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