rallyit Posted September 12, 2006 Share Posted September 12, 2006 Hi there fellow enthusiastsMY 3.9 TR7 V8 has a strange oil pressure problem , it get good pressure cold about 45-50lbs warms up to about 20-25 at idle fairly normal for a rover I would have thought. The strange thing however is that at revs ( constant revs ) the pressure falls constantly to eventually under 10lbs and in competition to almost zero. when allowed to idle will slowly come back up again but takes quite some time.I have replaced the pump gears, relief valve and spring all new. replaced the oil filter and the oil, Has anyone any experience to lead me in the right direction with this?CheersMatt Link to comment Share on other sites More sharing options...
TR Tony Posted September 12, 2006 Share Posted September 12, 2006 Hi Matt,I had something similar in my 3.5 V8 not long after I bought it. I would get 35 -40 lbs pressure when cold, falling to around 20 -25 when warm, but after 5 - 10 miles or so as the oil got hotter the pressure would fall away to around 10 lbs. The RV8 should run 30 - 35 lbs at 2400 rpm when hot, & 10 -15 lbs at idle when hot. Yours may be higher if you have an uprated pressure relief spring - many do especially for competition use.I am sorry to tell you that with my engine the falling oil pressure was a sign of a failing big end bearing, & all too soon it began to knock, heralding an engine rebuild :'(Is your oil warning light connected as well as the gauge - if that is working but does not come on then it could just be a faulty pressure sender or gauge, but I would be careful. Do you have facilities to drop the sump & take a look at the bottom end? Link to comment Share on other sites More sharing options...
rallyit Posted September 12, 2006 Author Share Posted September 12, 2006 ThanksBut mine does this straight from cold even though it has good pressure say 50 lb as soon as you rev it and hold it there it will fall quite quickly. the as soon as you let it idle it will stabilise back to normal. I suspect that bearing failure will be a constant where this varies simply with revs ( gets worse )When hot all this is ecentuated , the motor runs fine otherwise. ThanksMatt Link to comment Share on other sites More sharing options...
Beans Posted September 12, 2006 Share Posted September 12, 2006 As you changed everything pump related (and pressuming it was done correctly) there are only two options left;The first one is oil surge. But if I read your post correctly it also occurs when stationary, allthough I hope I have overlooked something;So only one option left to me, the bearings are on the way out :-/ Link to comment Share on other sites More sharing options...
Roger Keys Posted September 12, 2006 Share Posted September 12, 2006 Got to agree, sounds very bearing like to me. Link to comment Share on other sites More sharing options...
TR Tony Posted September 13, 2006 Share Posted September 13, 2006 Matt, if you are sure the falling pressure is not bearing related then the only other cause of symptoms like this that I have experienced was due to a cracked block.Admittedly it was in a Ford 1600 Xflow engine, but I had exactly what you describe. Engine ran fine, pressure good at idle & initially when driving but would gradually fall away to virtually nothing. If I then stopped & just let the engine idle the pressure would build back again. Drive off again & the symptoms would be repeated. A strip down revealed an internal crack in the block.I sure hope it is not bearings or a cracked block, but if you can't find any fault with the gauge or sender, & you have already changed the pump gears etc, I don't know what else it could be :(Fingers crossed that I am wrong. Maybe worth a phone call to one of the V8 specialists - I spoke to V8 Developements once & they were very helpful even though I did not do any business with them in the end.http://www.v8developments.co.uk/ Link to comment Share on other sites More sharing options...
rallyit Posted September 13, 2006 Author Share Posted September 13, 2006 Thanks Guys,I am talking to steve at S&S also, its a bit of a curly one as bearings appear to be okCheersMatt Link to comment Share on other sites More sharing options...
rallyit Posted September 19, 2006 Author Share Posted September 19, 2006 Ok ,Keep this one for the books, we found that because we have a heavily modified/ baffled sump and due to the positioning of the baffles we have done away with the pick up pipe support bar. This inturn allowed the pipe bolts to work very slightly loose and suck a small amount of air as the flow increased, it would be perfect at idle, perfect on a quick rev but as soon as it maintianed revs ( high flow ) it caused low pressure area around the gasket and sucked in air.Tightened the tube FIXED! Thanks all for your feedbackCheersMatt Link to comment Share on other sites More sharing options...
Beans Posted September 19, 2006 Share Posted September 19, 2006 Glad to hear it turned out to be only a "minor" problem ;) Link to comment Share on other sites More sharing options...
TR Tony Posted September 19, 2006 Share Posted September 19, 2006 Great news Matt. See - I kept my fingers crossed & I was wrong! :D Link to comment Share on other sites More sharing options...
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