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jtz54
Novice
Mar 17, 2008, 7:31 AM
Post #1 of 4
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Crankcase Pressure
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I have a 2000 Suzuki Grand Vitara with 170K miles. Until recently the vehicle has never given me a problem except now the lifters have been clacking noisily at startup.
One thing I noticed is that when I remove the oil cap there is no longer any positive crankcase pressure as before. When I used to loosen the cap with the engine running, there was always air coming from the crankcase, now there is nothing. I know that on any other vehicles I've seen there is always positive pressure in the crankcase. I've put in a new PVC valve with no results.
Any ideas on what happened to cause this?
(This post was edited by jtz54 on Mar 17, 2008, 7:32 AM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 18, 2008, 1:39 AM
Post #2 of 4
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Re: Crankcase Pressure
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It's getting there with the miles. Forget the oil cap for now - how good have you been with oil changes? Any sludge noted? The crankcase should be at a slight vacuum with a healthy engine and at some point the blowby of high mile engines or abused ones overcomes the PCV system. It's manageable for a while if that's what's happening but the beginning of the end.
Change out oil with synthetics and perhaps up the viscosity may help for now,
T
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jtz54
Novice
Mar 18, 2008, 6:46 AM
Post #3 of 4
(4115 views)
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Re: Crankcase Pressure
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Thanks for the reply! I'm not sure what's happened. I do know that everytime I've loosened the oil cap I've felt positive pressure from the crankcase. I just bought a 2002 Volvo S40 with 86K and it has positive pressure. Is this a bad thing?
I've used synthetic oil for over 30 years and have always had excellent results with minimal sludge. Since this valve lifter issue started I've used this stuff called Auto-RX with good results (contains lanolin which conditions seals, which I'm told synthetic oil isn't the friendliest towards). The oil holes in the lifters of the Suzuki engine are minimal and sludge easily. The Auto-RX seems to have cleaned them out. I was thinking that the lack of crankcase pressure may be due to the oil pump going out (although oil pressure is OK).
Appreciate your inputs.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 18, 2008, 10:36 AM
Post #4 of 4
(4111 views)
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Re: Crankcase Pressure
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Ok: Just under the oil cap is usually close to or on valve covers. Air motion there varies in different vehicles/engines - the dipstick tube is a better indicator of crankcase pressure in more cases but not all again. The idea is for the vapors in the crankcase to be returned thru a PCV system into the intake and crancase would measure a slight vacuum of pressure. It the pressure is higher than atmospheric it blows out of any gaskets or open dipstick tube, oil cap - get confusing but it is not supposed to be pressured in there as that is an indication of gasses blowing by worn piston rings common as engine get up there in miles, time and or abuse.
Oil pressure may still read strong when you are running but may be late to build up when first started. It's excellent when an engine has up to a normal pressure when cranking even and they slowly lose that over their life as oil is pressuring up in bearings and other areas first and the more worn the longer it takes.
Hydraulic lifter are not the first to get oil when started and if other items before them take up too much of the bounty they are frequently the first sign by ticking which may quit after a while or may persist and mechanical repair is indicated.
You could check the oil pressure with a gauge that is not part of the vehicle to get accurate reading to see if it is able to do the job.
Over the life of an engine the oil must resist making like a shallac and sludge which will clog the little holes the oild must travel to lubricate the items thruought the engine. Lifter make noise when they get stickey from shallac or not adequate oil pressure early enough and the pin point heat of friction will turn even the best oils into sludge. I've seen the synthetics resist that tendency better than conventional but all must be changed regularly - like every 3,000 miles with few exceptions.
At 170,000 miles I think you are witnessing the signs of wear on the engine.
Opinion: From new most engines will deliver 100,000 miles of dependable life with few problems with ordinary care. The next 100,000 depends on how rigorous the care was and the quality of oil used and throw in good luck. We hear of engines with tons more miles but they are the few after the 200k mark - many still run but running perfectly well is unusual by that point. The manufacturer's aim seems to be for the 100k for the whole car and in real life it varies widely. The whole vehicle is involved - not just the engine.
Just changing oil is like a cleansing of existing unseen sludge and that varnish mentioned. The solvents to speed that up like flushes can cause problems by being too fast. When ticking first starts accellerating the change intervals might reverse some conditions or at least can't hurt.
I'm not there taking in every tidbit I might notice in a vehicle with that mileage on it to be sure of anything. Basically over a career of automotive I would tell folks that they have done well when they can reach the miles you already have - and the rest is gravy usually earned with care for it along the way. How many miles do you expect without some major work? There is a life expectany with the best of care,
T
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