covincharger 0 Posted July 10, 2006 did cold compression test.tested from right to left as looking at pic. 130==175==160==160 can anyone tell me what this means.cheers Quote Share this post Link to post Share on other sites
jinx 0 Posted July 10, 2006 Could be a few things.... 1) The low cylinder is leaking air past the piston rings. You can check this by running the test again, only this time pour a LITTLE new engine oil into the cylinder through the spark plug hole...(no more than a teaspoon full as you risk hydrostatic lock and bent conrods etc). If the compression improves with the addition of the oil then your piston rings aren't sealing as well as they should be. 2) Your are losing compression through your inlet or exhaust valve on that cylinder. Can't really be checked, more of an instinct/experience thing. You can however take off the rocker cover and pour a little oil around the cam buckets on that cyliner, turn you're engine over and see if the oil bubbles....can get very messy very quickly...!! 3) Bad News.....You could have a crack in the cylinder wall of that low cylinder which means that you are losing some of the compression......until the piston rings have gone past the upper extremities of the crack(s) and are sealing as normal again. Can't tell if it is this really without engine strip. You may however get compression in your sump which will be evident in the crank case breather tube. 4) You have a cracked head and are losing pressure into one of many places eg exhaust port, coolant, oil system etc. Bad news! 5) You have a leaky head gasket, either straight from the cylinder to atmosphere, or into your coolant/oil system. You can sometimes work this out by a) never ending supply of air into your coolant; When engine is stationary coolant should leak into your cylider....Does your coolant smell like exhaust smoke or petrol? Are you losing coolant? Do you have mayo in your oil...a by product of the coolant dripping into the cylinder and running past the piston rings into the sump. b) Similar thing with oil...are you losing any etc......Do you have blue exhaust smoke? c) You can check the leak to atmosphere by squirting water mixed with washing up liquid around the the head gasket with engine running....Bubbles equals leak. However, not all doom and gloom, If your car is running fine then i wouldn't worry about it....just comp test it regularly and see if the values improve /get worse. One more point....get car up to running temperature then comp test it to see if you get more consistant results. Hope this helps........ :thumbleft: Quote Share this post Link to post Share on other sites
covincharger 0 Posted July 10, 2006 cheers,havent got mayo in cap ,smokes a bit of white on hard revs.what compression should they read from cold.engines done 140k. Quote Share this post Link to post Share on other sites
jinx 0 Posted July 10, 2006 White smoke normally indicates water getting turned to steam somewhere along the line...ie cylinders or exhaust. If you are losing a lot of coolant then i would look at head gasket as a possible failure point....but without looking at it it is difficult to say. Not sure what the Comp figs are...i am sure someone on here with a bentley manual will be able to tell you..... Quote Share this post Link to post Share on other sites
