Darren-B Posted March 17, 2013 Posted March 17, 2013 Where are you located? Might be worth speaking to a specialist near you for an experienced opinion before jumping in & striping the engine down if your not 100% sure what your looking for. Quote
Ebized Posted March 17, 2013 Posted March 17, 2013 Where are you located? Might be worth speaking to a specialist near you for an experienced opinion before jumping in & striping the engine down if your not 100% sure what your looking for. +1 If you mention where you are located someone can point you in th right specialist direction. Edit: OK checking back through your posts I see you are based near Skipton so if any member on here can advise a good local(ish) specialist where Gareth might like to get his car investgated further before an engine removal and strip? Quote
Lexx Posted March 17, 2013 Posted March 17, 2013 (edited) Atkins are nearby (Malton). Falcon are in Boro. Edited March 17, 2013 by Lexx Quote
Ebized Posted March 17, 2013 Posted March 17, 2013 Thanks Lexx - 2 highly regarded independents on here Quote
gareth29 Posted March 17, 2013 Author Posted March 17, 2013 Thanks for those names chaps. I've now taken the rocker cover off and I'm going to have a look at the intake valve lifters to try and see if one of the springs is broken. Quote
ZMANALEX Posted March 17, 2013 Posted March 17, 2013 You will not see the spring as the bucket covers the spring and the cam covers the bucket.. Alex. Quote
gareth29 Posted March 17, 2013 Author Posted March 17, 2013 Yes but thought i could see if one wasnt working properly by pressing down on it and comparing its action with the others? Quote
ZMANALEX Posted March 17, 2013 Posted March 17, 2013 A compression test and a cyl. leakage test would tell you that. Quote
gareth29 Posted March 17, 2013 Author Posted March 17, 2013 My thought is that the broken spring is causing the valve to close too slowly and therefore still be slightly open when ignition takes place (I did a compression test and it was fine). How does a cylinder leakage test work? Quote
Lexx Posted March 18, 2013 Posted March 18, 2013 Put in a known amount of compressed air into a cylinder (known pressure). Measure how much leaks out over a set period of time. Quote
Chris AME Posted March 18, 2013 Posted March 18, 2013 Get your self a leak down and compression test done on all cylinders so you can compare the results. does the problem only occur when blipping the throttle or at all times? Also have you checked the gaps on the spark plugs, i would be checking everything on the ignition front before commiting to an engine strip Quote
gareth29 Posted March 18, 2013 Author Posted March 18, 2013 The "popping back" is happening all the time, but it really barks when you blip the throttle - it is only happening on no. 6 - the inlet tract is very black. Compression on this cylinder was about 180psi when i checked it. Quote
Chris AME Posted March 18, 2013 Posted March 18, 2013 get a leakdown test done, keep any running to a minimum as if it is a sticking valve or a broken valve spring you dont want the piston coming up while the valve is still open Quote
gareth29 Posted March 18, 2013 Author Posted March 18, 2013 Thanks atkin666, have read up on the leak down test now - but may as well have a look at the valve lifter action now it exposed. Trouble is i have no garage and its dark cold and snowy! Quote
gareth29 Posted March 31, 2013 Author Posted March 31, 2013 After a short interlude due to flu and poor weather, just taken a look at the valve lifters - seem fine. Then I noticed that as I was turning the crank, that part of the exhaust camshaft wasnt turning! Turns out it has sheared, just after the saddle on top of cylinder no.4 and the rearmost bit that is supposed to work no.6's exhaust valves is loose and has not been working. So the exhaust valves on no.6 are permanently closed and hot combustion gas has been making its way back out of the inlet valves when they opened, causing the backfire. See photo below. Anybody heard of this happening before? Quote
ZMANALEX Posted March 31, 2013 Posted March 31, 2013 PM received and replied to: Cam shafts are in stock and good to go same/next day. Alex. Quote
cs2000 Posted March 31, 2013 Posted March 31, 2013 wow a sheared camshaft... I cant even see how that would have happened unless a piston got stuck somehow but then I cant even see how that would happen either. Good diagnosis work though Quote
The Chubby Ninja Posted March 31, 2013 Posted March 31, 2013 Glad you have finally found the problem. You should go for some aftermarket cams for a bit more power. Then again its probably alot more expensive Quote
gareth29 Posted March 31, 2013 Author Posted March 31, 2013 yeah, its a big relief to finally nail the problem - started taking off all the bits from the front of the engine this afternoon to get access to the timing cover. Cam-wise its probably going to be a used item from zmanalex - might give nissan a call tho, cos it is a very unusual problem i suspect - manufacturing defect? Quote
gareth29 Posted April 2, 2013 Author Posted April 2, 2013 Removed the rear part of the cam today - the bolts holding the cam brackets down were only finger tight!! Assume that the cam was whipping around, only held properly by the centre bracket - where it snapped. Took off the timing chain cover as well - the view behind is a work of art - and who knew that cleaning off all that old silicone could be so much fun. LOL Quote
cs2000 Posted April 2, 2013 Posted April 2, 2013 I love the looks of inside of some engines, not brave enough to do it myself though! Hope this new part sorts out your issues, another Zed saved ! Quote
The Chubby Ninja Posted April 2, 2013 Posted April 2, 2013 Yeah maybe worth saying to nissan but they will probably just say its been rebuilt at some point and not done right but worth a try though. Its definitely not a common problem Quote
gareth29 Posted April 17, 2013 Author Posted April 17, 2013 Finished the job at the weekend - car started 1st time and sounds fab and is delivering loads of creamy, smooth power! Balanced a glass of water on top of the plenum - not a ripple to be seen. Been out for lots of little test drives with family and friends - driving the 9 miles to work is fun too. Only fly in the ointment is a small oil leak that i thought would be cured when i re-sealed the front timing chain case, but it turns out its dripping onto the top of the a/c compressor from somewhere else. Massive relief that its all working properly Thanks to all who posted helpful comments. Quote
The Chubby Ninja Posted April 17, 2013 Posted April 17, 2013 congratulations. bet that's a huge relief to get it all sorted. now to finally enjoy the zed Quote
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