Mj17 Posted July 5, 2014 Share Posted July 5, 2014 Hi,As I said in an earlier thread I started getting a mechanical noise around 3500RPM on the way back from the Le Mans 24hrs the other week and finally managed to get through my list of other niggles and fit an oil pressure gauge last night, so today I took it for a run... Yes...Cold pressure was OK, between 50 and 75 lb/ft or 5 kg/cm.Warm oil pressure wasn't quite so pretty, down to 1 kg/cm or 15 to 20 lb/ft.I know it's impossible to say without seeing but the car still seems to run and pull fine, with the noise still not kicking in until 3500RPM but I'm off to France for a week on the 25th (2 and a bit weeks time). Am I likely to get away with just replacing the bearings (will check with a friend tomorrow but don't think there's any crank movement so thrust washers OK), or would I be better off dropping it in to a garage, so they have time to get anything else fixed?I'm off to have a little cry now :( Quote Link to comment Share on other sites More sharing options...
ferny Posted July 5, 2014 Share Posted July 5, 2014 What RPM are those readings at? Idle pressures mean naff all (15-20lb at idle is good though), unless it's pretty much zero. What's its 3000rpm pressure like when hot? Quote Link to comment Share on other sites More sharing options...
Mj17 Posted July 5, 2014 Author Share Posted July 5, 2014 1 kg/cm (15-20 lb/ft) at 2000RPM rising to 2 kg/cm (30 lb/ft) at 3000RPM hot and not much more at 3500RPM - all while driving, not just reving in neutral.Pressure started to drop below 1 kg/cm as revs dropped below 2000RPM, so I kept them above.For some reason the car was idling at 2000RPM today (thankfully!) but that's and an ignition warning light that keeps coming on very slightly are the least of my worries right now. Quote Link to comment Share on other sites More sharing options...
Nick Jones Posted July 5, 2014 Share Posted July 5, 2014 Ok, pressure is low.However, I still think you've caught it early enough to get benefit from a shell change. Drop the sump and swap the big ends and mains. I might be inclined to leave the front main alone if the back one doesn't look too shot (front main is least loaded) as accessing it means removing the bridge piece and breaking gaskets that can't be replaced properly.With that oil pressure I'd also be inclined to investigate the oil pump (possible lapping of gears/housing and end plate to reduce scoring and end float) and the relief valve.Easy to fit new thrust washers while you have the rear main cap off. Should be good for a few more years.Nick Quote Link to comment Share on other sites More sharing options...
Mj17 Posted July 5, 2014 Author Share Posted July 5, 2014 Thanks Nick, you've pulled me back form running around in circles going "Oh-my-god, oh-my-god, oh-my-god" to just quite sobbing in the corner! Quote Link to comment Share on other sites More sharing options...
Mj17 Posted July 6, 2014 Author Share Posted July 6, 2014 Well started stripping the bottom end down today, partly to see how good/bad it looked and partly to find out what size bearing shells I needed to order and, well mixed news.The good news is that both main and rod surfaces I looked at seems OK - no scoring visible of detectable to the touch.Bearing shells, both rod and main had seen better days though, with the rod shell showing some brass at one end and the main being mostly brass. While they look scored they aren't actually too bad (it's mainly just different colouration of the metal with the one at the top the only one you can feelwith a fingernail), with only the faintest lines you can feel running a fingernail across them.The oil pump doesn't look to good though. Body to piston gap is fine but piston/piston is only just withing tolerance and I can get a feeler gauge under by straight edge with easy so end-float is way out to bounds. Worst of all is the way the parts look though.First off there's clear signs of metal-on-metal running between the shaft and the pump body, along with pitting on the surface of the shaft part of the pump (but this doesn't contact anything so maybe isn't a problem?).There's also clear metal-on-metal scoring between the outer part of the pump and the body, both ends and outside edge.Nothing very clear on the shells to say what size they are - "0448" and "2E 01" on the rod bearing and "M341 010 MG" on the main. Does that sound like +0.010 over-sized?Unfortunately I'm back up to Edinburgh for work first thing Monday so not able to measure the journals themselves (and don't have time to leave it till next weekend to measure/then order parts). Quote Link to comment Share on other sites More sharing options...
junkuser Posted July 6, 2014 Share Posted July 6, 2014 Looks like grit damage to the pump. Requires replacing.Any gritty stuff in the sump? Quote Link to comment Share on other sites More sharing options...
Phwoar Posted July 7, 2014 Share Posted July 7, 2014 Not worth risking the consequences of a dodgy oil pump, replace it. Quote Link to comment Share on other sites More sharing options...
nang Posted July 7, 2014 Share Posted July 7, 2014 Unless you are able to measure the journals I can't see much point in guessing they're ok and spend good money (and time) in buying new ones.Do the job once and do it properly. (eek)Tony. Quote Link to comment Share on other sites More sharing options...
Mj17 Posted July 12, 2014 Author Share Posted July 12, 2014 Well after about 12 hours on my back under the car I now have; new rod bearings, new main bearings, one new thrust bearing (standard and +5 fitted but I only,had +5 and +10 so replaced +5 and crossed fingers).Only time for a quick, in town traffic test drive and so far 5psi at 1,000rpm, falling to 3bar (44psi) at idle 800rpm idle when warn - so looking promising...As I said at the start I didn't have time to measure the journals but so far crossed fingers looking good (touching more wood than used to build the Mary Rose whilst typing). Quote Link to comment Share on other sites More sharing options...
ferny Posted July 13, 2014 Share Posted July 13, 2014 Mj17 wrote: (touching more wood than used to build the Mary Rose whilst typing).Hmmm... Just don't overload it on the way to France and take the corners a bit easy, yeah? Quote Link to comment Share on other sites More sharing options...
Nick Jones Posted July 13, 2014 Share Posted July 13, 2014 Well done. Presumably you renewed the oil pump? - the old one looks shot!Nick Quote Link to comment Share on other sites More sharing options...
tiggrr1 Posted July 13, 2014 Share Posted July 13, 2014 The bottom end of my GT6 looked EXACTLY the same as that when I stripped it down (sump off engine in car) and I also changed Mains big ends and thrusts too along with a new oil pump.Did the 2013 10CR shortly after and it still shows around 60psi at around 3000 rpm after a long prolonged thrash and around 20 psi on tickover, I use Penrite HPR30which is a 20w60 oil and I reckon it helps keep the oil pressure up on a long hot run.I think on my next oil change (soon) I'll use VR1 just to see if there is a difference, both are really good quality oils but I suspect it may give a little less oil pressure.Of course that may be completely wrong but only one way for me to find out is to compare like with like. Quote Link to comment Share on other sites More sharing options...
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