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Leadbut
10-29-2007, 03:13 PM
Just got my newly rebuilt 390 back in the old AMX. Fires up nice. Plenty of power.
Just when things are looking up. My oil Pressures drops off to about 5 psi after about 6 miles (190-200F).
Starts up fine about 55-65 psi cold.
Holds nice for a little while then just falls away.
Engine sounds great. Although I haven't driven it around at 5psi. I checked the gauge it operates fine. If i let it go long enough the idiot light comes on. Pulled the oil pump apart and there is some wear, but the clearances are in spec. I pulled out the Oil pressure bypass valve it seams OK, but it’s a very tight fit in the housing. The spring is new. I'm at my wits end I don't want to pull the motor again!

BREK
10-29-2007, 04:03 PM
Does the plunger move freely without the spring in place? Have you tried changing filters?

Leadbut
10-29-2007, 04:10 PM
With the spring out the plunger is tight.

I had to use a screw driver to get it out.
when Iput it back togeter the pressure of the spring is enough to reseat the plunger.

jeepsr4ever
10-29-2007, 11:49 PM
Hmmm I wonder if your oil is draining back fast enough. Try adding 1.5 qts and see if it makes a difference.

Leadbut
10-30-2007, 07:16 AM
I'll try that tonight.
During the rebuild I added the lifter valley bypass line. Could this be having an effect?

The pressure was low before the rebuild (not this low though).
Bearing clearances were still in spec when I disassembled the motor.

Could the oil pressure relief valve be so tight that it's getting stuck when the temp rises and the aluminium housing expands? Or does the passage the plunger is in actually get larger because the passage expands outward?

Does the plunger have a seat like a valve? Or does it just block the passage?

jeepsr4ever
10-30-2007, 09:49 AM
When the temp raises the plunger actually becomes looser in the hole. I would be suspicious of either oil drainback or that valley line. Often valley lines hit the bottom of the intake and when you use a soft material (copper ect) you can easily tear the end off when installing the intake (if the bottom hits the fitting between the lifter banks)

Leadbut
10-30-2007, 11:03 AM
That’s what I Thought, but one of the eggheads at work had a theory that the Stainless steel plunger would expand because it is in contact with the hot oil and that the aluminum housing with its greater mass and exposure to the cooling air... coefficient of expansion 23 vs. 17... blah, blah... spring pressure reduced by...internal differential pressure... blah...blah.... some story about his father-in-laws motorcycle.... blah...blah...ham and cheese sandwich for lunch...etc.etc.

I used braided hose for the valley by-pass. But it was a pain in the ass getting the intake on. I didn’t have to force anything but it took some screwing around.

Everything is new on this thing except the timing cover oil pump housing and the fuel pump.
If the oil was contaminated with fuel wouldn’t I smell it and see it in the oil?

jeepsr4ever
10-30-2007, 11:16 AM
You may not see it but you would definately smell it. It is possible your valley line is leaking under pressure. This might mean a intake removal and inspection while priming the pump.

tufcj
10-30-2007, 11:43 AM
3 things I can think of to check.

1. Do you have a newer oil pump cover without the filter bypass?
You might replace it with the newer model without the bypass.

2. Oil filter brand.
My CJ sees 10-15 PSI less pressure hot when using a Fram filter vs. a NAPA Gold (Wix).

3. Have you replaced the pressure relief spring?
I've seen the springs fatigue from years of heat. A new spring will sometimes restore pressure.

Any doubt on the relief plunger, pull it and clean it and the passage with generous amounts of carb cleaner.

Bob
tufcj

Leadbut
10-30-2007, 12:01 PM
I have an old style cover with the oil filter bypass in it. I pulled it out and blocked it with a nut and bolt.
There is a FRAM filter on it now. When I started it up to breaking the cam I had a WIX filter on it. I changed the oil on late Sunday during half-time and I could only get a FRAM at the local shop.
I'll put another WIX on it or a NAPA gold then add 1.5 quarts of oil and see what happens.
If that doesn't do it I’ll start pulling things apart.

If the oil pan to oil pick up clearance is off would this make a difference only when the oil is hot? Wouldn’t it starve the pump all the time?

ironman_gq
10-30-2007, 01:40 PM
when you did the valley line did you strip the motor down and clean out all the passages to remove metal shavings? these can go through the bearings and tear things up in a hurry.

Leadbut
10-30-2007, 02:06 PM
Yup, I did a complete block up rebuild.
everything new

mike4089
10-30-2007, 04:27 PM
I have an old style cover with the oil filter bypass in it. I pulled it out and blocked it with a nut and bolt.
There is a FRAM filter on it now. When I started it up to breaking the cam I had a WIX filter on it. I changed the oil on late Sunday during half-time and I could only get a FRAM at the local shop.
I'll put another WIX on it or a NAPA gold then add 1.5 quarts of oil and see what happens.
If that doesn't do it I’ll start pulling things apart.

If the oil pan to oil pick up clearance is off would this make a difference only when the oil is hot? Wouldn’t it starve the pump all the time?


someone answer this because ive always had this problem..i also did a block up reuild....and when you say change the filter and add 1.5 quarts are you saying to add 6.5 quarts total???...is it safe to run that way??

AMX69PHATTY
10-30-2007, 07:19 PM
Not to but in, but have read here to run "extra oil" since drainback can be slow.

On the Pressure Relief Plunger, somewhere in a post here MC posted what the diameter and tolerance was for the plunger. A new plunger I got in a Sealed Power Kit was a little "big" on diameter, stuck closed and start up, and bulged the oil filter, Napa Gold, pretty good, but thankfully didn't burst it and make a BIG mess. Checked diameter of an old plunger, is was .0005 to .001 smaller diameter, used it and pressure spikes went away. Wonder if your relief plunger is sticking open cause it's a little on the "big" diameter side ? Does the Plunger bore in the filter adpater look smooth and polished ? I'm no expert, just a novice. Thread for me to learn from. Hope ya get it figured out and squared away soon.

Leadbut
11-01-2007, 12:16 PM
Well i added the 1.5 quarts extra and put on a good old Wix filter.
Once again the car started up great oil pressure cold. Got out on the road to see what would happen. I was sitting at a stop sign about half a mile down the road I sat there for a few minutes to get a good read on the idle Oil pressure before I got started. I figured id go about 2-3 miles and stop again.
Well I soon as I took off I got pulled over by a cop. He'd seen me sitting at the stop sign, and figured i was up to no good. So when i went roaring past him glass packs and all he pulled me over. Thankfully he had a sense of humor and curiosity. He was only about 26 and he'd never even heard of AMC never mind seen an AMX. So we shot the shit about cars, and it turned out we had served in Iraq at the same time in the same division . He forgot about my ticket and I forgot about the rest of my test drive (till tomorrow!)
Today I pulled off the oil pressure gauge pick up assembly and cleaned it out. It's attached to the pressure gauge and the idiot light. I was thinking I might have shot a piece of crud up there or filled it with Vaseline on startup. It looked pretty clean though.
When I was out last night my oil psi didn’t drop lower than 15psi at idle. But my mechanical pressure gauge seemed to move very jerky. Like it was sticking. It used to move very smoothly. What does that mean? Air in gauge line? Relief valve sticking? Nothing?

Leadbut
11-03-2007, 06:25 AM
Got out last night.

Fired right up good pressure

Engine warmed up to about 190 still at about 15psi idle and about 40 under load.

Drove a couple more miles (maybe 3-4) Still around 200F but only about 5 psi idle and 20-25 under load.

Drove home and hit the bottle.

Everything is new except the Timing cover/oil pump housing.

jeepsr4ever
11-03-2007, 08:13 AM
You may just have excessive clearances in your oil pump.

Leadbut
11-03-2007, 10:43 AM
I think your right. I should have put on a new one from the start.
It looked OK. Measured out loose but in spec. I cleaned up the pump cover. I never checked but it my have a taper in it and the outside clearances could be a lot bigger than I think.
Either way by replacing it I will at least eliminate the pump from the equation.

fifesjeep
12-06-2007, 09:18 AM
I was having "issues" with my oiling on the 360... 1st the plunger would get stuck and as soon as I would fire-up the 360 my oil filters blew apart... my oil pressure gauge got "tweaked"... With the engine off it reads 18psi (I can only imagine what the actual pressure reached)... After I took the pump apart I machined the plunger down almost .001" and did a quick hone on the bore... After that, I milled the bottom plate removing all grooves etc... After that, I lapped it in on a lapping block/table... The reason I did all of this was the gear pocket (Where gears are contained) there wasn't any scratches or marks.. Only the bottom plate had a few "marks"... I packed her full of vasoline button her up and she purred 58-62ish at cold idle and 28-30 during warm idle 180*... After a few hundred miles I noticed my oil pressure dropped pretty quickly... I yanked the pump and it looked mint... The it dawned on me... The Internal oiling line.. I only snugged it... Well, I yanked the intake and sure enough it wasn't snug no-more... I tightened it down and I'm good to go.

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