Paul Herts Posted June 15, 2018 Report Share Posted June 15, 2018 I have an oil catch tank which collects vented oil from the block and rocker cover and at the moment it is probably half full but has always worked pretty flawlessly as its not exactly a complicated arrangement. The last two times I have used the car oil is being discharged from the fill cap on the rocker cover. Can any one advise whats gone wrong or how to fix this? Quote Link to post Share on other sites
Mike C Posted June 15, 2018 Report Share Posted June 15, 2018 Make sure the catch can is venting freely. In many designs a small air filter is located where the orange cap is on yours. Quote Link to post Share on other sites
stuart Posted June 15, 2018 Report Share Posted June 15, 2018 Empty the tank out and check the hoses to it arent blocked too. Stuart. Quote Link to post Share on other sites
john.r.davies Posted June 15, 2018 Report Share Posted June 15, 2018 (edited) Paul, Yours looks very like one of these: https://www.google.co.uk/search?q=oil+catch+tank&tbm=isch&tbs=rimg:CWaWzcGkHU4HIjjH9iqD_1vuavRJ1l4GYIq3MtljUncFn3q372m4KWdO5KNDea53yVRXxC_1PA8TGnH00EOZAavP6-xioSCcf2KoP--5q9EUWvyfhR7O_15KhIJEnWXgZgircwRAEmegJu2apgqEgm2WNSdwWferREv_1udGfXUUiCoSCfvabgpZ07koEScZY4BbdSVvKhIJ0N5rnfJVFfER6O68e6ti-QsqEgkL88DxMacfTRFtRHc7qvjwVSoSCQQ5kBq8_1r7GEUtWtrfx9B82&tbo=u&sa=X&ved=2ahUKEwjrr_7_6NXbAhUKPhQKHWh0D1oQ9C96BAgBEBg&biw=1920&bih=947&dpr=1 Most of those, and yours, suffer from two defects: 1/ They have no external vent, unless that orange cap is vented 2/ They have no drain connection. A catch tank's purpose is to collect crankcase gases, allow oil vapour to condense and return the liquid to the sump, and to vent gas and water vapour to the atmosphere. The first requires a connection from the base of the tank to the sump (or else to the hole in the crank case where a mechanical fuel pump would sit) and the second a small filter on the top, to help retain oil droplets. Some of the look-alikes to yours have a sight tube, so you can tell if it's full, but I suspect yours is, so that crankcase gases have nowhere to go, except out of the filler cap. You will have the unpleasant task of emptying it, either by a drain plug, or by removing it and tipping it out. "Please dispose of the effluent carefully"! John Edited June 15, 2018 by john.r.davies Quote Link to post Share on other sites
Peter Cobbold Posted June 15, 2018 Report Share Posted June 15, 2018 Most of the vented gas is water vapour form blow-by. And most of the trapped liquid will be condensate: disgusting brown watery stuff, with a bit of oil mixed in. Blow-by is created by ring wear, and the filter-free Webers wont be helping that. Peter Quote Link to post Share on other sites
Andy Moltu Posted June 18, 2018 Report Share Posted June 18, 2018 Another thing to consider is that your catch tank sits with low with thepipe from the rocker pointing down to it. At high revs quite a bit of oil splash will be flung into the pipe. Unless it is baffled or initially points uphill there will be nothing to prevent that o8l splash going straight to your catch tank. Ideally you might want to increase the bore of the crank breather thus reducing the pressure to reduce leakages elsewhere and angle it uphill to drain oil splash back to the rocker. Quote Link to post Share on other sites
Steves_TR6 Posted June 18, 2018 Report Share Posted June 18, 2018 (edited) And if the rocker cover cap is leaking it might need a new gasket Mine seems to need a new cork gasket every couple of years I cut a new one out of sheet gasket thats available cheaply Steve Edited June 18, 2018 by Steves_TR6 Quote Link to post Share on other sites
Mike C Posted June 18, 2018 Report Share Posted June 18, 2018 If you suspect ring blow by a wet and dry compression test will give you a good indication of the state of your piston rings. Quote Link to post Share on other sites
stuart Posted June 19, 2018 Report Share Posted June 19, 2018 You will also find those rocker covers dont have a baffle plate behind the breather pipe which means a lot more oil can go straight out of the cover. Stuart. Quote Link to post Share on other sites
john.r.davies Posted June 19, 2018 Report Share Posted June 19, 2018 If you suspect ring blow by a wet and dry compression test will give you a good indication of the state of your piston rings. Wet and dry compression tests the state of the valves, not the rings. The oil will always increase the seal of the rings, but make no difference to a leaky valve. A less objective test is to take off the oil filler cap while the reconsidered up and running. A gentle breeze is normal, anything's suggest poorly dealing rings. John Quote Link to post Share on other sites
Mike C Posted June 19, 2018 Report Share Posted June 19, 2018 Wet and dry compression tests the state of the valves, not the rings. The oil will always increase the seal of the rings, but make no difference to a leaky valve. A less objective test is to take off the oil filler cap while the reconsidered up and running. A gentle breeze is normal, anything's suggest poorly dealing rings. John I've always thought of the test along the same lines as these people: https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=20&cad=rja&uact=8&ved=0ahUKEwiP4sW3zN_bAhUGhrwKHR1JACYQFgh-MBM&url=https%3A%2F%2Fwww.freeasestudyguides.com%2Fcompression-test-injecting-oil.html&usg=AOvVaw1L54lfN9dnOHUSuB1ksiHs Quote Link to post Share on other sites
john.r.davies Posted June 19, 2018 Report Share Posted June 19, 2018 MIke, that says, "If the compression increases, the piston rings are at fault." But wetting the rings with oil will always increase the pressure. John Quote Link to post Share on other sites
KiwiTR6 Posted June 20, 2018 Report Share Posted June 20, 2018 A leak-down test is much more useful and the equipment not expensive these days, although the procedure itself is somewhat more complicated. https://en.wikipedia.org/wiki/Leak-down_tester Around 20 pounds on eBay. Quote Link to post Share on other sites
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