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Compression test results


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7 replies to this topic

#1 BCSubguy

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Posted 26 February 2005 - 12:05 PM

Checked a couple more things on the '92 loyale-

1- burped out lotsa air from cooling system....had no further sounds of waves crashing through heater core!

2- cleaned up air control valve

3- checked and adjusted throttle valve

4- metered coolant temp. sensor....first tests showed resistance higher with heat (no where near spec.) subsequent tests now show O.L. - got a new one on order.

This all brought the idle down to approx. 1200 rpm., the temps wouldn't rise above half and for a joyous moment the cel was extinquished! ( I thought maybe the bulb had finally burnt out!) - thankfully it re-lit! Damn code 34.

All cylinders show 90 psi on first crank, then after another 4 or five cranks get up to #1- 90....125 ,#2- 90....145 ,#3- 90....130 ,#4- 90....135.

A couple drops of oil brings them all consistantly up
#1- 100....180, #2- 120....240, #3- 120....200, #4- 120....175.
The oil test wasn't totally scientific as I didn't have a good oil dropper- some may have gotten more than others! (#2!!)

I guess the question is how low can you go? What are typical comp. values on these? It sounds as good as it ever has...took it for a small test drive- temps seemed o.k. If the new temp sensor drops my revs down to a more acceptable range I may just leave it till it shows more signs of age...then do a major overhaul? Anyone with any thoughts on this?

#2 Vanislru

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Posted 26 February 2005 - 01:04 PM

Those results aren't too bad, I'd run it till you really need a teardown. On my rallywagon[not in sig] I pulled it apart after many abusive miles to sort out a comp. prob and found the rings all gummed up, I cleaned em threw the motor back in and it still runs tight after 20k. As for the CTS make sure that the contacts in the connector are clean, most often that's the problem. If you only developed 90psi after several cranks then I'd be thinking about a ring job/reseal.

#3 grossgary

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Posted 26 February 2005 - 01:20 PM

#1- 125
#2- 145
#3- 130
#4- 135

did you prop the throttle body open and remove ALL the spark plugs when doing this compression test? if you don't, this can make your compression results less accurate and cause further variation between cylinders.

no matter the method used, these values look fine to me. i would not be concerned about a block showing these numbers unless there is some other issue. unless there are other major problems i would expect this block to be reliable beyond the life of many other parts on the vehicle.

#4 torxxx

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Posted 26 February 2005 - 03:19 PM

yeah those numbers are fine. You ARE supposed to crank it 4 or 5 times to get a proper reading, because when you started, that piston may have already been half way up the cylinder.

As long as your numbers are above 115 psi you are fine. Hell I drove a loyale sedan home last week that had 0 Psi and a bent valve on the #1 cylinder

#5 grossgary

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Posted 26 February 2005 - 03:24 PM

same here, i drove an XT5 (XT6 with a dead cylinder) with no problems. once was spark plug wire not connected another time was bad HLA's on that cylinder. drove it awhile on the fault HLA's before i got around to fixing it.

#6 BCSubguy

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Posted 26 February 2005 - 07:08 PM

Yup, warm engine, throttle open. Drove it to town and back-(120km) no probs. Last 30 comes with a 1000ft. elevation gain. I think it'll be o.k.

Thanks all for the input. Cheers:drunk:

#1- 125
#2- 145
#3- 130
#4- 135

did you prop the throttle body open and remove ALL the spark plugs when doing this compression test? if you don't, this can make your compression results less accurate and cause further variation between cylinders.

no matter the method used, these values look fine to me. i would not be concerned about a block showing these numbers unless there is some other issue. unless there are other major problems i would expect this block to be reliable beyond the life of many other parts on the vehicle.



#7 Nug

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Posted 26 February 2005 - 09:01 PM

Historically, compression numbers are supposed to be within a 10% difference of each other.

Of course, after I say that, I think it's 20%. I forget. Anyway, those numbers seem acceptable.

#8 bushbasher

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Posted 27 February 2005 - 12:16 AM

if theres more than a 20psi difference I get worried, 10 I wouldnt get worried about unless it was a motor used for performance not commuting.




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