-= Quick write-up for the archives: Checking compression (1.8T) =-
01-23-2005, 06:25 PM
#1
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-= Quick write-up for the archives: Checking compression (1.8T) =-
How to check compression on my 1.8T? There's plenty of info in various posts in the archives--thought I'd just sum it up into one. Nothing new here, just a concise post for the archives..
You'll obviously need a compression test kit, which can be found at Sears or your local SnapOn truck. The one pictured below was from Harbor Freight (my local Sears had none in stock), and I <b>would not</b> recommend it. So, consider the picture for reference only.
<img src="http://images8.fotki.com/v145/photos/4/48510/1705981/P1090102-vi.jpg">
<b><i>On a warm engine....</i>
1) Pull all coilpacks and plugs
<img src="http://images7.fotki.com/v117/photos/4/48510/1705981/P1090094-vi.jpg">
2) Pull 15A fuel pump fuse (#28)
<img src="http://images7.fotki.com/v144/photos/4/48510/1705981/P1090093-vi.jpg">
3) Ideally, you'd want to hook up your battery to an external charger so that it doesn't drain--which might affect your readings. It's not <i>crucial</i> IMO (I didn't use one and my readings seem fine). But if your readings seem to drop off a cliff like this: 180, 175, 170, 160....you might blame the battery and not your cylinders. Just depends on the condition of your battery I suppose.
4) Screw in the hose carefully, then connect to the gauge.
5) Start cranking. [For nDBW, hold the gas pedal to the floor while turning over for each cylinder. For DBW, you could pull the intake hose and prop the throttle plate open] I turned the engine over <i>exactly</i> 6 times per cylinder, as the reading had leveled off at that point. <u>(The most important thing here is to treat all cylinders exactly the same. If you don't, then you may get inaccurate readings.)</u> Repeat for all cylinders. That's it!
</b>
So what's a normal reading? Well, Bentley claims anywhere from 144-190psi is within spec. The more important, general rule of thumb is that all cylinders should be within 10% of each other.
On my '97, with 122K, the readings were: 168, 165, 175, and 172.
Oh, why don't I recommend the HF compression tester? <b>It was just plain inaccurate</b>. My initial readings with the HF gauge were: 147, 149, 137, 145. I went back with a SnapOn gauge and got consistently higher numbers.
Good luck.
Andy
Search keywords: compression checker gauge tester test compression readings cylinders.
You'll obviously need a compression test kit, which can be found at Sears or your local SnapOn truck. The one pictured below was from Harbor Freight (my local Sears had none in stock), and I <b>would not</b> recommend it. So, consider the picture for reference only.
<img src="http://images8.fotki.com/v145/photos/4/48510/1705981/P1090102-vi.jpg">
<b><i>On a warm engine....</i>
1) Pull all coilpacks and plugs
<img src="http://images7.fotki.com/v117/photos/4/48510/1705981/P1090094-vi.jpg">
2) Pull 15A fuel pump fuse (#28)
<img src="http://images7.fotki.com/v144/photos/4/48510/1705981/P1090093-vi.jpg">
3) Ideally, you'd want to hook up your battery to an external charger so that it doesn't drain--which might affect your readings. It's not <i>crucial</i> IMO (I didn't use one and my readings seem fine). But if your readings seem to drop off a cliff like this: 180, 175, 170, 160....you might blame the battery and not your cylinders. Just depends on the condition of your battery I suppose.
4) Screw in the hose carefully, then connect to the gauge.
5) Start cranking. [For nDBW, hold the gas pedal to the floor while turning over for each cylinder. For DBW, you could pull the intake hose and prop the throttle plate open] I turned the engine over <i>exactly</i> 6 times per cylinder, as the reading had leveled off at that point. <u>(The most important thing here is to treat all cylinders exactly the same. If you don't, then you may get inaccurate readings.)</u> Repeat for all cylinders. That's it!
</b>
So what's a normal reading? Well, Bentley claims anywhere from 144-190psi is within spec. The more important, general rule of thumb is that all cylinders should be within 10% of each other.
On my '97, with 122K, the readings were: 168, 165, 175, and 172.
Oh, why don't I recommend the HF compression tester? <b>It was just plain inaccurate</b>. My initial readings with the HF gauge were: 147, 149, 137, 145. I went back with a SnapOn gauge and got consistently higher numbers.
Good luck.
Andy
Search keywords: compression checker gauge tester test compression readings cylinders.
Last edited by Kris Hansen; 04-29-2009 at 09:42 AM. Reason: added to wiki
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01-23-2005, 07:01 PM
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Don't forget...
Firstly write engine (and oil to be really precise) temp down, and write down what readings you get because that will be the only true test on YOUR car. Also Snap-On sells a leak down adapter for little less than price of comp-tester so if you do have loss you can see where it is coming from.
