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Guest Message by DevFuse
 

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what should my compression test at


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33 replies to this topic

#1 jeffast

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Posted 25 September 2005 - 08:51 PM

well the title i was curiouse what compression my car should test at currently i am getting withen 5psi of 120 per cylender
edit: i know this sounds stupid but i am having power issues
also how far up the temp gauge does the needle ride on your car?

#2 THE ROSS

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Posted 26 September 2005 - 12:27 AM

my needle only rises up to 1/4 of the way...don't know if that is normal or not, I just bought it a few days ago.

#3 SuBrat84

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Posted 26 September 2005 - 12:34 AM

Is this the car in your sig.? My XT6 tested around 160-170psi in each cyl.. I don't think 120 is bad though. Sure someone else would know better. All my sube's at normal operating temp are between 1/3 - 1/2 on the gauge.

#4 jeffast

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Posted 26 September 2005 - 08:52 PM

k thanks

this combind with the rate it eats oil men i need to get my new engine ready now

#5 ShawnW

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Posted 26 September 2005 - 10:57 PM

Yup, thats low. A leak down would tell more about rings, etc. Temp gauge on a Subaru with analog gauges reads just under half usually theres a mark around there to kindof give you an idea where it ought to be.

#6 kingbobdole

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Posted 26 September 2005 - 11:06 PM

120 sounds low.... Did you test it warm or cold?
My temp gauge has changed over the years... When it first was AT it read about the 3/4 mark.... Then I got the mt and it went to 1/2, then I changed the head gaskets (went byebye) and redid the cooling system and added the hood scoop... now it chills at the 1/4 mark. anywhere 1/4-1/2 is ok.... if its higher you probably need cooling system work... hoses, pump, T-stat, RAD cap or simply a flush with some new juice....

#7 jeffast

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Posted 27 September 2005 - 11:35 PM

no problems persay i am just the kind of person who worries allot
i guess my temp hgauge is fine then i am used to my truck 1/8 th of the way up when warm
i know this is really bad but my car is eating more than a quart and a half of oil in a month any guesses as to when my engine will die?
i need to pull lets say six to 8 months out of it till i can finish my new one
Edit: i tested cold i have a $400 subaru raditor in my car that is 4-5 months old i put a thermostate in 5 days ago because the after market one was wrong temp i have been rinning thermostatless for 2 months also both my caps are new and i flushed the system when i did the raditor

#8 nipper

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Posted 27 September 2005 - 11:51 PM

DO a wet and dry compression test. I am assuimng you already did the dry one. Take all the plugs out and squirt some oil in the cylinders. Crank the engine and if the compression goes up you have bad rings. If it doesnt you have bad valves. Sounds like you can have bad rings or worn valve guides.

This should help

http://automotive.my...w.spy?artid=593

nipper

#9 All_talk

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Posted 28 September 2005 - 10:16 AM

Chart from the FSM for EA82/T

Posted Image

Gary

#10 jeffast

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Posted 28 September 2005 - 09:20 PM

evrey one thank you i will try the oil trick the next warm day

i am pretty sure it is valves because the last time my car sat for more than a week there was allot of blue smoke the first 10 seconds or so i ran it
edit: nevermind i won't be trying the oil trick when i read the article it says it won't work on subaru engines

#11 nipper

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Posted 28 September 2005 - 09:40 PM

evrey one thank you i will try the oil trick the next warm day

I am pretty sure it is valves because the last time my car sat for more than a week there was allot of blue smoke the first 10 seconds or so i ran it
edit: nevermind i won't be trying the oil trick when i read the article it says it won't work on subaru engines


Really? i must have missed that part.

Lets start with a blank slate

hrmmmm, Well if all your compression numbers are over 100 psi and even, lets assume thigs are ok. That leaves valve stem seals or valve guides. How much oil do you burn?

What kind of power issues are you having?

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#12 jeffast

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Posted 28 September 2005 - 11:00 PM

i burn 1-2 quarts a month and power wise it just doesn't have the guts it should i mean their is no pull what soever once you leave second and it takes over 2 miles straight level road to break 100 and it won't go over 105

#13 nipper

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Posted 28 September 2005 - 11:29 PM

Does it idle fine otherwise? can you see the blue exhaust, is it on acceleration or decleration. i think accelertaion is valves, and deceleration is rings. Also loss of power is rings. Oil past the valves are valve seals and guides.

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#14 bulwnkl

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Posted 29 September 2005 - 09:53 AM

Deceleration smoke is usually valve guide seals (the increased vacuum when you close the throttle sucks oil past the seals) while acceleration smoke is more likely rings and possibly other sources also. Did I understand right that this is your XT6, or a turbo XT? A turbo car this could be a turbo problem.

As stated, the "oil squirt" thing won't work on a horizontal engine. Compression testing should be done with the engine fully warm and with the throttle wide open. Pull all the plugs at once and disconnect the coil and fuel injection control (spraying raw fuel in all the cylinders will wash the oil off them and cause a lower reading from poor ring seal). Then immediately start the test so you still have as much oil as possible in the ring area to make a seal.

#15 nipper

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Posted 29 September 2005 - 10:17 AM

If its a turbo i mised that... turbo oil seals can cause high oil consumption. Also if the turbo is seized or dragging you will have lots of power and running issues.

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#16 jeffast

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Posted 29 September 2005 - 09:48 PM

xt-6 i am planning to trubo charge it but i have to replace the engine first either way i cannon tell when it is blowing smoke i have seen it smoke once it had been sitting for a week waiting for a new alternator it has a small oil drip but that is like a drop a day nothing comes out while the engine is running

#17 gbrand

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Posted 29 September 2005 - 10:29 PM

As far as the "oil squirt" not working on a horizontal engine i beg to differ

1) theory-the oil will "squish" around the rings as the piston goes up and down-and provide a better seal if the rings are worn.Think about it-by the same logic the "oil squirt" shouldn't work on a V8 or any engine where the cylinders are not vertical. And that is not the case.

2) practice-When the EA71 in my 80 wagon started running like crap one day, I limped it back home and ran a compression test. 20 psi in one cylinder, others fine. Not ever hearing the "oil squirt" won't work, I tried it and comp in the bad cyl raised to 60psi-grrrrrr was hoping for a bad valve.........Professional engine rebuilder diagnosed problem after teardown to rings losing thier tension/tempering from thier heat treating. Unfortunatley they couldn't ever get thier act together to rebuild the engine so I picked up the parts(no charge) and dropped in a crate engine.

#18 quattroPilot

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Posted 29 September 2005 - 10:34 PM

although I have a turbo, I do have N/A pistons. To chase a major problem (which has resulted in engine extraction and FULL dismantle) I checked compression -cold engine, "dry"- and I got 150psi dead even across the board EXCEPT for one cylinder...it measured an astounding 60psi

heheh, turns out this was the cylinder with cracked piston, one compression ring broken, and a severely mushed oil ring. Needless to say that was the causation of my performance problem (AFTER I'd accused the turbo for 3months, replaced it with a used unit, had the original rebuilt and then R&R'd back into the motor).

So I'd say if you have a strong 120 then that's not too bad. Could be higher, but might just be caused by some trivial problem (especially if it's uniform across the banks), like disfunctional headgasket, valves and/or stem seals, etc.

#19 jeffast

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Posted 30 September 2005 - 10:49 PM

i dunno i am planning to tear down my spare enging this weekend the get it machined and rebuild it
so i really only need to pull a few more months out of it
also now i have a giant coolant leak yayPosted Image
occasionally it idles fast but that is it

#20 BoostedBalls

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Posted 30 September 2005 - 11:04 PM

also, make sure the throttle is WIDE OPEN if it wasn't already. Do it dry, then wet and see if it increased by more than 20%. Leakdown is a better check but a cheapy tester is $50.

#21 jeffast

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Posted 01 October 2005 - 11:55 PM

the throttle wasn't i'll make sure to check

#22 jeffast

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Posted 02 October 2005 - 09:55 PM

i was checking coolant flow with the cap at a gas station the other night and at one point i saw a bunch of little bubbles in the coolant does this mean my head gaskets are shot the car consumes almost no coolant but it did have over heating issues when i bought it a raditor that wasn't welded shut fixed that

#23 nipper

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Posted 02 October 2005 - 10:04 PM

Subarus dont become steam engines when they have a head gasket issue, they tend to throw up once it gets really bad.
Was the car warmed up when you saw the bubbles? The lack of heat is not a good sign...
Can you have a shop sniff it for exhaust gases in the radiator?

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#24 jeffast

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Posted 02 October 2005 - 10:21 PM

it was warm and yes it threw up infront of my house3 + times
EDIT:however it was over filled the third time

#25 nipper

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Posted 02 October 2005 - 10:34 PM

There really is only one reason why soobies tend to throw up .... HG, but do get a sniff test just to be sure.


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