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97 4cyc oil pressure!!

Hi!

I've read many posts here about the lousy oil sending units in these jeeps. Well, dropping off to zero is really scary, so I decided to attach a mechanical oil pressure gauge to determine what is really going on with this pressure. When cold, this engine has around 30-40 lbs pressure at idle, but when hot, it normally hovers around 30 at highway speeds, and will drop to zero most often at idle. The mechanical gauge never shows it dropping to zero, but to 9 or 10 lbs at idle. The owners manual states that 13lbs at idle is acceptable. I know the possible causes are oil pump, air leak at pick-up tube, perhaps dirty screen, and bearings. This engine has 110,000 miles on it, with no unusual engine noises that would maybe indicate bearings. It really doesn't sound any different than it did 3 or 4 years ago.. Sometimes I hear what sounds kinda like a valve lifter, or maybe just common cylinder noise. Any ideas??

cal

Reply to
Cal
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I would just keep fresh oil and filters in it and realize it is showing it's age. The only real fix is a rebuild.

Fresh oil does wonders top keeping the pressure up, when mine starts to drop when hot, I know it is time for a change.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Cal wrote:

Reply to
Mike Romain

You can also use heavier weight oil to prop up the pressure readings.

Reply to
BillyRay

You can but you will cause further wear of the oil pump or failure all together. Dodge Rams had issues with oil pumps failing a an extreme high rate and after all said and done it was discovered that the owners were using 20w50 oil on 99% of the failures. Thicker is not better, nor does it protect better than a thinner oil. 5w30 and 10w30 oils provide better viscosity and more wear protection in vehicles that specify them. Heavy oils such as 10w40 or 20w50 in vehicles that do not specify the heavy weight oil will cause damage to the oil pump. As Mike said just change your oil.

Reply to
Coasty

Reply to
L.W.( ßill ) Hughes III

I would not think using 20w-50 in an engine designed for 10w-30 that has

110,000 miles would put undue strain on the oil pump. Thicker oil would "make up" for some of the excess gap in a worn out oil pump.

Nor do I regard 10w-40 and 20w-50 as "heavy" oils. Until relatively recently 10w-40 was considered a "standard" weight oil. Heavy weight oils such as "straight" 40, 50, and 70 weight were used in high pressure, high power, high altitude, and super-charged engines.

Frequent oil and filter changes are important as well as the type of oil itself. I use synthetic or synthetic blend oil which can have the effect of "lowering" oil pressure (a measurement of resistance to flow) because of its naturally superior fluidity (the inverse of viscosity)

Reply to
BillyRay

Reply to
L.W.( ßill ) Hughes III

Note my earlier post: 91YJ Mileage Milestone, 7/10/2005. I've run Vavoline Maxlife 20/50 the last 150,000 miles except in winter when I change to

20/40. Oil pressure is steady at 45-50psi at rpm above 1500. At idle, stays steady at 35psi. Also, I believe that when the oil sending unit fails it pegs at max on the oil pressure gauge not zero. That's been my experience with two previous failures.
Reply to
reconair

I used 20w-50 for a number of years in the wintertime (in Ohio) and straight

30 weight Zoildeeze (spellin'?) or Series 3 in the summer because of it high detergent package. In later years I used Rotella T 15w-40 year round for the same reason.

I now use synthetic or synthetic blend oil.

Reply to
BillyRay

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