I wandered around Colorado for the past few weeks. Lots of opportunity for downgrades that require a downshift to 2nd (or even 1st) gear to control speed and these can last 10-20 miles. Climbing the coolant temps and oil pressure are usually constant. Almost boring. Downshift to use compression braking and the temps remain constant and the oil pressure ticks up a tad. Less than beginning oil pressure on a 40F degree cold start. So we are not talking about a large jump. One theory is that the crank rides in the crank bearing differently on deceleration. The motor is healthy---I am just curious why does oil pressure rise. We are not talking about huge revs. Figure 2500-4000. 0-20 full synthetic.
Oil Pressure Chg Downshifted on Long Grades (1 Viewer)
- Thread starter chilibit
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gaijin
GOLD Star
The oil pressure gauge on my 200 is no more helpful than the backup oil pressure light.
When I first bought my 2013 LC200, I noticed the oil pressure gauge did not move much. I brought this to the attention of my dealer who confirmed the issue. They subsequently replaced the oil pressure sender, manually monitored oil pressure in real time, escalated the complaint to regional and finally corporate tech at Toyota. Final verdict was that's just the way it is. If the oil pressure gauge shows ANY pressure, you're OK - I've learned to live with it.
So, to your point, trying to analyze minor fluctuations in a gauge that is inexact at best, is fruitless in my opinion.
HTH
When I first bought my 2013 LC200, I noticed the oil pressure gauge did not move much. I brought this to the attention of my dealer who confirmed the issue. They subsequently replaced the oil pressure sender, manually monitored oil pressure in real time, escalated the complaint to regional and finally corporate tech at Toyota. Final verdict was that's just the way it is. If the oil pressure gauge shows ANY pressure, you're OK - I've learned to live with it.
So, to your point, trying to analyze minor fluctuations in a gauge that is inexact at best, is fruitless in my opinion.
HTH
- Thread starter
- #3
I think you may be confusing meter variance, or perhaps system variance, with my condition where I do this and I get the same result invariably. I am using the term variance as a statistical concept. I think there is an engineering reason for the behavior and I am curious to understand those factors. Here is a quote from a different site. Since the 200 gauges are only relative indicators I don't really know what the pressure difference is. The motor has 30k miles and I feel it is pristine. No oil consumption.
"The oil feed holes are located in the top of the main saddle. High vacuum on deceleration lifts the crank closer to the holes allowing the pressure to rise. When you press on the gas, cylinder pressure pushes the crank away from the oil holes causing the pressure to drop......."
At this point all I have is a working theory. Thank you for your input Gaijin.
"The oil feed holes are located in the top of the main saddle. High vacuum on deceleration lifts the crank closer to the holes allowing the pressure to rise. When you press on the gas, cylinder pressure pushes the crank away from the oil holes causing the pressure to drop......."
At this point all I have is a working theory. Thank you for your input Gaijin.
The concept would seem to make sense. But the bearing tolerances are very tight, so I wouldn't think there would be a large enough difference between the two states to allow significantly more oil to leak through.
- Thread starter
- #5
I follow you. When I brought up the question to the master mechanic for Land Cruisers that I am lucky to have found his first reaction was 'how much of a pressure spike.' And then explained that the worse the spike then the more suspect the bearings. I think I would never have noticed anything during my normal usage here in Kentucky. Curiosity then played it's card. The quote I included above likely referred to a domestic small block motor and not a Toyota design. I think my motor is just fine---it was one of those 'I never thought of that' moments.
