Just started today.. Cold the pressure is around 60. As the engine get warms its 30 - 35.. Now driving down the road (3000) the pressure drops to 20+. Lift the throttle slightly (drop down to 2500) the pressure goes back to 30 +.. Nail the throttle and the pressure will drop to 18 - 20 and move up to 20 - 22.
Lift the throttle and the pressure goes back to 30+.. At a stop with engine running and in gear the pressure drops to 10. I am running mobil 1.
Normal pan with a high vol. oil pump, New Autometer Mech Oil guage with new lines.
Picking up air in the pump? Dont notice any abrupt movement, just slow and steady.
Help!

 

Sounds like you are low on oil and/or the pan is getting sucked dry. A few other member have commented about needed a higher volume oil pan with the high volume oil pumps.

BTW Are you leaking any oil? My first engine leaked and burnt oil and every once in a while I would be low in the pan and loose pressure like you describe.

 

Not enough oil.

Colin

 

I agree.

Paul

 

Checked the oil last night... Little above the line.. Orginal dipstick and I change my own oil so the amount is correct. Did discover a small leak at the oil connector and corrected it but no change as of this morning.. Drops on Accerlation. Any other suggestions?

 

Your "upgraded" high volume oil pump is likely scavenging all the oil from the oil pan. Srop back to a standard volume oil pump and you should be fine.

 

You did get me to thinking.. As this has just started, do you think that the screen could have shifted/moved to the point that it would be cavatating?

 

I'll make a leap here, assume oil drainbacks in heads & lifter valley are reasonably clean, not sludged, not plugged. Yes, the pickup could've shifted ... but unless you've got one tabbed to the op ... then it'd probably've fallen off too. I don't necessarily think the HV op is the root cause. I suggest pull the pan. The screen could be clogged/partially clogged by silicone bits etc ... it don't take much. If it ain't loose or clogged, the height may be wrong. Pickup/screen should be 1/4" off pan ... too much & you're above oil ... too little & it could be sucking/bending the pan up into the pickup. Often the screen will not sit square with pan ... make sure the area of OPEN screen (WIRE) that's FURTHEST away from pan is set at 1/4"... measure with clay ... it'll be tough to do in car but can be done. While you're in there, pull the cover off pump & pull the gears ... inspect gear cavity & gears. BTW, most HV ops also come with a HIGH PRESSURE SPRING installed ... along with a normal pressure spring in the box. If you haven't done so, change to normal spring ... it'll still make more volume, just not high pressure.

 

Looks like I am pulling the pan this weekend. My machine shop also stated that it could be the bypass on the filter or the pump.. Now to add more to the story, just ran it up easy to about 100 and the hard brake to make my turn and the pressure guage went to ZERO!!! :eek: NADA :eek: NOTHING :mad

 

I suggest parking it asap. It's apparently been starving ... and with today's antics ... it'd pay to pull a few caps & look at bearings ... start at the front & work back. Go ahead & cut open the filter for a look. G'Luck!

 

Do this and get an oil sample from http://www.blackstone-labs.com/ They'll be able to tell you what wear metals are in the oil.

Colin


[Modified by Colin, 3:18 AM 11/9/2002]

 

I found all kind of interesting things when I got under the car this evening. Little shiny flakes in the filter... Not alot but more than what I wanted to see.

2.5 maybe 3gts of oil drained from the pan.. Droped the pan and noticed that the dip stick was laying on top of the oil pump screen.. Also discovered that the op screen could move (with little pressure) up and down in the pump. In fact I was able to remove the screen from the pump with little effort!!!

Pulled the #2 rod and the bearing is shot. Luckly no damage to the crank.. #7 rod look ok but could see that there was a problem. PUlled the first main journal and again the bearing is shot but the crank was not damaged..
I guess it is new bearing time!!!
Has anyone replaced rod and main bearings without pulling the engine?
Will it never end!!

 

Read this first about rod bolt stretch. I use the ARP lube method.:
http://www.chevyhiperformance.com/editorial/article.jsp?id=49258& viewtype=text


You got something not right in your engine to eat those bearings. I too would try replacing the bearing but I wold ditch the high volume pump too just to eliminate that as being the cause. First pull all your spark plugs since you will need to push the pistons up then pull them back down. Next rotate the crank till one od the crank journals is pointing strait down then pull both rod caps. Here's a trick to protect the crank, cut 4 pieces of 3/8" fuel line about 3 inches each then put them on the 4 rod bolts. This will keep the rod threads from scoring the crank journals. Next push those pistons up just enough in their bore to clean the journals, maybe an inch (I used a breaker bar and rubber hammer to tap the bottom of the piston) to get any left over bearing material out. I used brake cleaner to clean up the area. After cleaning the area and rods up, the rod/bearing contact area needs to be clean and dry, lube the inner part (part that touched the crank journal-I used cam break in lubricant) of the two upper bearings and put them in place then pull on the rods to get them in place. Pull the fuel line off the rod bolts then put the lower bearing in the cap and lube the mating surface as you did with the upper bearing. At this point use the ARP lube mention in the article I linked to and follow the torqueing procedure described. Rotate the crank and do the other bearing as needed. I used this method but my crank and rods had been damaged and it ate the bearings again. Hope you have better luck.

BTW prime your oil pump again until oil is coming up out of all the push rods, takes about 10 minutes in a new dry system but may take shorter since you have resudual oil in your engine. I would run the engine for half hour then change your oil again. Drive it a day or so and then change it again. Drive it a week and change it again, at this point it should have little or no beaing in the used oil/filter.

Again hope you are lucky and this cures what ails your engine.


[Modified by Fevre, 7:09 AM 11/9/2002]

 

Thanks for the link, I used the ARP lube when I put the engine together. No I have replaced a crank without removing the engine (Never do that again) but I have never replaced the main bearings this way. Do I push the top bearing out by rotating the crank?