Main bearings?

[aarolar]

So now I've got the hydraulics straight and all the other little nit picky things cleaned up on my TO-35/Z134 I need to address my oil pressure issues. After running my 5 foot tiller for about 45mins to an hour the pressure drops to 20psi at 1/2 throttle and at idle it reads 0 on my new gauge. When cold it reads 25 at 1/2 and 20 at idle, what's confusing is the motor runs extremely well and has 150lbs compression so its like someone resleeved and ringed it but didn't do any bottom end work.

Now my question is how feasible is it to go into the motor and only replace the main bearings and rebuild the oil pump. Being I just spent about 800$ on a new top cover and other hydraulic parts a full engine rebuild just isn't in the picture right now but I really need this thing mowing in a few months. Any thoughts are appreciated both good and bad.
 

[matt p]

just a few questions? what type of oil ,did you test your oil pressure gauge with air pressure to check its accuracy any oil leaks!!
I had a leak right below the gauge at the 90 degree fitting.
 

[aarolar]

No oil leaks that's one of my pet peeves, I am running 15w40 with a quart of Lucas and no I have not checked the gauge with air.
 

[Tony in Mass.]

Confusious say, one should not open a can of worms unless he likes worms....
 

[2tractors]

First and formost, where is the gauge from, sub it out, 2nd and formost is the screen clogged, 3rd. where is the gauge from, but last its a z134 so we ALL have experience. Once those 3 things are eliminated, re-- check all.Then, depending on how many times you want to drop the pan its once for each, pan gaskets leak-- twice to 3 times, rod plasti guage once, mains once,So you could have bad mains, rod bearings,guage, and even if the temp guage mal functions, the compressions figures being measured while cold are still impressive but only muddy the waters.I'm guessing the gauge has some green on the display and is NEW!
 

[aarolar]

[IrvIA]

All the suggestions are correct, but I'd take a hard look at the oil pump. They're noted for it. Mine was bad but ran good.
 

[Dick New York]

First , check the guage , or replace it with a new one . Being that the pressure drops when hot , it is probably not the guage , but that is a good place to start .
Second , pull the base , and check the pump . Sounds like they are a weak point .
Third , plastiguage the mains that you can access , and the rod bearings .
?? Do you hear any knocks when it is hot . Have someone explain to you the different conditions , and sounds of rod , and main bearing knocks . They sound different , and happen under different operating conditions .
A bad main bearing can be annoying for a long time , but running with a bad main can cause damage over a period of time .
A rod bearing is more serious . It will only knock for a short time . The bearing will eventually spin , and sieze on the crank , and when it goes , it is a disaster . Chances are good that if a rod goes , it will ventilate the side of the block because it will break the rod when the bearing siezes .
Good luck
 

[aarolar]

No I'm not getting any knocking at all how would you test the gauge? Is using compressed air accurate enough?
 

[trac]

What i have done to check the gauge: Turn down the
air presser i have two gauges on my airtank 1 reads
the presser in the tank the other reads whats coming
out of tank if you can turn down the air that's
coming out your good to go so start off at
15bls.read the gauge see how close it is.
 

[aarolar]

[2tractors]

Is the gauge from any of the 3rd world countries, if so its useless, had one reading 5 lbs. after warm up and put a stewart warner guage in and got 30 lbs cold and 25 hot.
 

[aarolar]

I'm sure its from the PRC, got some suggestions or links to a good gauge?

I just had another thought, could the oil filter cause a oil pressure drop? I ordered a spin on oil filter kit and it came with a fram filter that I couldn't get to quit leaking so I ran to town and got a Napa Gold. I noticed the fram had about eight or ten 5/16 holes in it for the return and the Napa Gold only had two 1/4 or smaller holes. I didn't run the fram long but I swear I had over 25 closer to 30lbs of oil pressure cold but with the Napa it won't go over 25 cold am I crazy or could this filter be that restricted?