vijay Posted July 18, 2008 Posted July 18, 2008 Hi, Does anyone have a link to a write up on the correct way to do a compression test? Cheers Vijay Quote
vijay Posted July 18, 2008 Author Posted July 18, 2008 found one http://www.twinturbo.net/nissan/300zx/FAQ/FAQpages/compression.html How much oil do you pour in if compression is low and what's a low figure? Vijay Quote
vijay Posted July 23, 2008 Author Posted July 23, 2008 if you get a low reading, what could be the cause? Quote
BIGSSS Posted July 23, 2008 Posted July 23, 2008 Worn rings, head gasket, stuck valves, piston damage, cracked head Quote
Yowser Posted July 23, 2008 Posted July 23, 2008 A few pointers - there is plenty more to add, and nothing is conclusive without further tests...but gives you some ideas - 150+ is a good strong engine Getting a bit tired at around 130 A poor dry test, but good wet test would indicate worn rings and/or bore damage. Will often see excess pressure through crankcase such as fumes out of oil filler cap, or pushing dipstick out. A very low figure or zero compression will usually indicate a holed piston. No significant difference between wet and dry, but 2 adjacent bores with low figures can indicate head gasket. WOuld need further investigation to prove though - such as Losing water, overheating, gasses in Cooling system..etc Heads (alloy) can warp Block (iron) can crack Quote
SMW1 Posted July 24, 2008 Posted July 24, 2008 (edited) Once you do a compression test and find a low reading. Do a cylinder leakage test and find the leak. Bubbles in the rad = head gasket hissing from the exhaust = outlet valves Bubbles from the rocker = piston rings / cracked piston or bore scratch. Hissing from the intake = inlet valves Edited July 24, 2008 by SMW1 added inlet valves Quote
j1mmytt Posted July 24, 2008 Posted July 24, 2008 Once you do a compression test and find a low reading. Do a cylinder leakage test and find the leak. Bubbles in the rad = head gasket hissing from the exhaust = outlet valves Bubbles from the rocker = piston rings / cracked piston or bore scratch. And from the intake? inlet valves? Quote
j1mmytt Posted July 24, 2008 Posted July 24, 2008 I sometimes get hissing from my backside.. what would that be then? Quote
Yowser Posted July 24, 2008 Posted July 24, 2008 I sometimes get hissing from my backside.. what would that be then? IIA valve / idle control valve , they often fail/leak, and result in a poor idle Quote
TopLess Posted July 24, 2008 Posted July 24, 2008 I sometimes get hissing from my backside.. what would that be then? You have been eating your own cooking :D:nelson: Quote
vijay Posted July 24, 2008 Author Posted July 24, 2008 cylinder leakage test, take it I need a bit of equipment for that?? Vijay Quote
Paul C Posted July 24, 2008 Posted July 24, 2008 I sometimes get hissing from my backside.. what would that be then? as said - worn ring! :rofl: Quote
j1mmytt Posted July 24, 2008 Posted July 24, 2008 IIA valve / idle control valve , they often fail/leak, and result in a poor idle haha legrath with the serious post :D Quote
Yowser Posted July 24, 2008 Posted July 24, 2008 haha legrath with the serious post :D it was too easy to make a joke reply :p Quote
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