d2alfa Posted January 5, 2018 Report Share Posted January 5, 2018 Hi Folks, Just noticed rattles from the rocker cover and on checking found that three cylinders had compressions around 160 but one was only 90. My assumption is that a valve is leaking and my intention is to replace the offender. The sump always seems wet so I intend to install a new gasket. The engine has probably done about 130k miles. Are there any other things I should consider with the sump and head off? Regards David Quote Link to post Share on other sites
Fireman049 Posted January 5, 2018 Report Share Posted January 5, 2018 Hi David ~ This might be a good time to renew the big end and main bearings as well as the oil pump? Check the crankshaft end float. (new thrust washers). Tom. Quote Link to post Share on other sites
Rob Salisbury Posted January 5, 2018 Report Share Posted January 5, 2018 To change the rear main bearing of a 4 pot with the engine still in the car you have to remove the gearbox and flywheel first, but all 4 big ends can be done, no need to remove the pistons from the bores if really pressed, just make sure the liners are secured before turning the crank. Cheers rob Quote Link to post Share on other sites
boxofbits Posted January 5, 2018 Report Share Posted January 5, 2018 Hi David You might find its a broken valve spring or bent valve. When running is there any excessive blue smoke from the exhaust? It might be worth removing the rocker cover first to check the springs and then clearances using a feeler guage, if not just to rule it in or out. Regards Kevin Quote Link to post Share on other sites
stillp Posted January 5, 2018 Report Share Posted January 5, 2018 What's the oil pressure like? Pete Quote Link to post Share on other sites
RogerH Posted January 5, 2018 Report Share Posted January 5, 2018 Hi David, when you say the sump always seems to be wet - what do you mean. Is there water in the oil - if so this could be corroded Fo8 seals at the bottom of the liners If you have the head off do not rotate the crank unless you have clamps on the liners. Roger Quote Link to post Share on other sites
d2alfa Posted January 5, 2018 Author Report Share Posted January 5, 2018 Hi, Thanks for the advice. The oil pressure appears ok. There is plenty (probably too much) blow back gasses around. No water has been found in the oil but the perimeter of the sump gasket shows plenty of oil around. I was hoping to avoid the big ends and pistons and would probably hand over to a specialist to carry out. Regards David Quote Link to post Share on other sites
john.r.davies Posted January 5, 2018 Report Share Posted January 5, 2018 Before dismantling, try the 'oil test'. After chev king all the compressions, repeat after tipping a teaspoonful of engine oil down the spark p!ughole. The oil will always increase the piston ring seal, unless they have fallen apart, but will not affect a poor valve seal. Do that while you can turn the easily, and your diagnosis is confirmed, or denied! John Quote Link to post Share on other sites
d2alfa Posted January 6, 2018 Author Report Share Posted January 6, 2018 Hi, Thanks Kevin & John. I have removed the rocker cover and the valve springs look conplete. Will now try the 'oil test' David Quote Link to post Share on other sites
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