# Oil Pump Problem-'99 Chevy Suburban



## Nutbuster (Mar 25, 2007)

OK Guys here are the prelims;
'99 Chevy Suburban, 4WD, 350 motor, Almost 300K miles. About 7 months ago I posted problem with low oil pressure and was positive I had a pump going out. Some of you guys thought it was something else but I had it replaced and sure enough the old pump was just worn out. The shop I took it to replaced the original with an aftermarket unit. I'm 18,000 down the road now on the new oil pump. I gotta tell ya, I work real hard taking care of this motor and I pay attention to it's every need. When this shop I took it to for the pump replacement looked under the hood they couldn't believe the motor had as many miles on it as it does. Long story short, it's been well taken care of. Anyway, the following problem arose last week. While at interstate speed my pressure runs normal around 40 to 45 PSI. At idle it runs around 25 to 30 PSI. I noticed last week while running if I have to load up on the brakes hard the oil pressure will drop to ZERO! It immediately comes back up after you get off of the brake. Needless to say this scared the heck outta me so I pulled over and checked the level. It was only about 1/2 qt. low so I brought it to the full mark with a spare bottle I had on hand. By the way, the truck uses about 1 quart every 7,500 miles. After bringing it up to full it still loses pressure all the way to zero. The pressure is also erratic at idle and while at speed with quick fluxuations in pressure of 5 to 10 PSI. I'm thinking I have a problem with the pressure relief valve in the new oil pump because of the fluxuations but am at a loss as to the drop in PSI to Zero when hard braking. It seems like it is losing suction!The shop is un-sure, but in my mind everything points to the new pump. it is NOT an OEM part either! Why they put an aftermarket part in such a hard to get to area is beyong me! Please respond Gear Heads I need another head to bounce this one off of!! My baby's sick and I gotta fix her!


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## mack1 (Nov 27, 2007)

> Some of you guys thought it was something else but I had it replaced and sure enough the old pump was just worn out.


Hi Nutbuster,

I remember that post and was probably one of those that thought that it might be something else......I might be wrong again, but here goes. 

Oil pumps are positive displacement pumps (gear type pumps). Its always covered and full of oil, hard metal gears and housing, very resistant to wear. A very strong foundation for pumping low volumes of oil. There is a spring and ball arrangement that functions as a regulator and all the excess oil that the pump pushes through is releaved by this ball and spring maintaining normal oil pressure. I once had that ball stick closed on a 53 Ford and at idle, it would peg the oil pressure gauge and blew the oil seal at the filter. Those pumps put out a lot of pressure (not a lot of volume) and unless the engine is severly worn out, it will keep normal pressure. 

The oil pump is positioned in a part of the engine that lets the pump's pickup tube and flared and screen covered end protude to the deepest part of the oil pan. You would have to be pretty low on oil for the oil to migrate forward under braking to cause no oil to be present under the tube bell. I noticed that you are on top of this situation when you topped off the oil level. 

If the screen was stopped up, it would cause low pressure because of pump inlet starvation.

If the pump's pickup pipe was dislodged from the pump, the intake would be above the normal level of oil and would cause the no/low pressure problem. 

If the relief valve (ball and spring) was stuck open, it would cause this problem.

If the backpressure from the engine was not there (bad leaking lifter or bearing dislodged on the crankshaft rod or main) the pressure would be low especially when the engine was running slow. Remember that the pump puts out a lot of pressure, but not a lot of volume. A heaver weight would show increased pressure in this case. 

I think I just told you all I know about oil pumps. If you need to know what to do if the Sargent in charge of the Hobby shop on an airforce base who thinks he is running a private repair shop can be circumvented, that is another story and I can help you with that one also.

Remember that only 14.7 psi (barementric pressure at sea level) is applied to the oil to get it into the inlet of the pump.....so it isn't hard to starve the inlet with stopped up screens and the like. 

Very best regards,
Mack1


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## Nutbuster (Mar 25, 2007)

Morning Mack. I appreciate the quick reply. Yea, believe it or not I had to explain to the shop about the pump being positive displacement and how the relief valve works. Kinda makes me wonder how these ole boys stayed in business. I myself have three suspicions, 
#1. there is a problem with the relief valve sticking or it could be with the spring- ya know it could have broken...reducing the active number of coils to properly hold the ball against the positive pressure.
#2. The pick-up tube has, or is, coming loose. Not being the guy who put the new pump in I don't know how the pick-up tube is retained. Is it bolted in? Or pressed?
#3. Being an aftermarket pump it could just have pre-maturely failed.

I have a one micron filter on my oil system. A NASA engineer developed this system and it keeps your oil CLEAN!!! So a stopped up intake screen is not the problem. Plus, when we had the pan off 18K ago which as I said earlier was about 7 months ago there was very, very little residue in the pan. I was there during that part of the disassembly as I was keenly interested in what I was going to find in the pan after 279K miles!

Lastly I do have one more tib bit of info. After bringing the level back to full that day I drove about 12 to 14 hours and lost 1/2 qt. of oil. It hasn't leaked out, I don't let the motor leak, all have always been fixed immediately when they start. The soot out of the tailpipe appears to be normal, dry black. Plus she doesn't smoke at all. There is no oil in the water side and none in the air box. The motor runs as quiet as you could ask for with no chattering at all.
Ideas? I'm leaning towards a new pump but don't want to go through that if the problem lies eleswhere.


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## Nutbuster (Mar 25, 2007)

OH one last thing Mack. I'm running 10W-30. After the oil pump was replaced I started using a heavier oil but I got too much valce chatter in the mornings when the motor is cold so I switched back to the lighter weight oil and the chatter stopped.


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## SABL (Jul 4, 2008)

Hi Nb,

With the symptom you describe, only one thought comes to mind. Perhaps to facilitate easier re-install of the oilpan, the mechanic/s altered or removed your oilpan baffle. It seems to be a matter of the oil shifting away from the sump area when the brakes are applied. 

I do have another thought, but it involves the galleyways and return passages for the oil. I have had to fix (clear) the oil passages on an older model Olds due to lack of drainage. If this were the case you would have mentioned fouled plugs near the rear of your engine. When oil lays on top of the heads it will seep past the valve-stem oil seals and foul the plugs... generally the rear plugs due to slight engine angle. This issue (fouling) might not occur if you are running hotter plugs or if you have installed anti-fouling inserts. But it could explain loss of oil not due to leakage..... I'm still going to guess the problem is the baffle.

The lighter weight oil is wise..... I carry better pressure with 5W-30W in my E350 (237K miles) than I do with a heavier oil. And to think, I used 50W Valvoline racing oil in my '57 Chevy when I was a kid.... 

The valve clatter was most likely caused by engine wear and the use of a heavier oil. With 300K miles you do have wear on the bearings, which is normal, and the heavy oil takes more time to reach the lifters. When the lifters clatter it means the top-end is running "dry" and without lubrication. Until the lifters are pressurized you are not getting any oil to the rocker assemblies. With your mileage you don't need undue wear.... the use of a lighter oil will extend the life of your engine.....IMHO.

Best of luck (keep us posted),
SABL


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## mack1 (Nov 27, 2007)

Hi Nutbuster,

Looks like you already knew as much as I did about oil pumps.:grin:



> A NASA engineer developed this system and it keeps your oil CLEAN!!! So a stopped up intake screen is not the problem.


Is that filter between the pickup and the pump, or the oil just so clean that sludge on the screen isn't possible? Not clear what you meant.
The one micron filter seems like it might be a little restrictive for motor oil. Only place I saw one that fine used in use was on a hydraulic system.
Maybe someone else might know and will jump in. I would have suspected a 10 micron would have been about right. How do you clean it, or is it replaced periodically? I wonder if you get pressure drop across the filter.

On the pickup tubes, I've seen both bolt-on and pressed-in pickup tubes and I don't recall what Cheve uses. My guess would be pressed in cause it's cheaper. 

Isn't it amazing that you can get 300 thousand miles out of an engine without rebuild? I remember the earlier engines would be drinking oil by the time they had 60 thousand on them. If your oil isn't leaking out, it has to be going through the tail pipe. 

The 10W30 is fine, I was just pointing out that thicker oil would show up as higher pressure if the problem was bearing ware. Just an indicator of what the problem might be, not a recomendation for normal use. 

Like you, I think you will just have to go into the pump to find the problem.
I wouldn't suspect the new pump, but who knows?

Best regards,
Mack1


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## SABL (Jul 4, 2008)

I see all 3 of us are here..... let's see what trouble we can cause.....LOL:grin:

If I dig a little I might find a Chevy oil pump within a few feet of where I am sitting....I think I have more parts in my puter room than in the "gradge".

The Chevy pump is a press in type of unit and any damage to the mating surface will cause lack of "suction" but I think lack of pressure would be present at all times.


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## Nutbuster (Mar 25, 2007)

LOL, I knew y'all would be asking questions about my oil refiner system. I installed a T fitting under the oil sending unit and feed the refiner filter with a 1/4" flexible tube to a filter housing I mounted under the hood on the drivers side in the front. The outlet from the filter assembly is fed back into the motor through the oil filler neck. Plumbing in this method does not interfer with the OEM filter system or the pumping actions of the pump. The system refines your oil 7 times an hour. There is a parish here in Louisiana that has installed these systems on all of their school buses and have driven all of the buses over 3 million miles w/o an oil change. (I'll bet that statement will light up discussions). I've seen analysis reports before, going back 4 years, and after, two years after install of these buses. The analysis comes back line item by line item of different things they test for but to shorten up everything one line item stands out, that of the Iron content. Before the year after year readings were something like 22 PPM, the next year 24PPM, then 26PPM, etc. After the refiner was installed the iron content dropped to 1 PPM the first year, and only 1 PPM the second year. The company guarantees 100K on your crankcase of oil or 6,000 hours. I met the owner of the company and he was driving a 99 burb just like mine. He was doing testing and had, believe this, 160K on his oil. At the time my oil, (before I installed the refiner) had 3,000 on it. The oil with 160K on it was cleaner and smelled better than the 3K oil in my motor. I contacted this company because of a recommendation from a friend in a similar business. We both log about 50 to 60K a year. Here is the link so you guys can check it out, http://www.petrosavers.us/ Ralph Leblanc, the owner, is a good guy. The oil in my motor has 18K on it and smells new! This system works!
I'm not selling, just sharing!
Onto the Suburban's problem.
SABL- I'm running OEM plugs that are pretty new. No fouling, and have not installed anti-fouling inserts.
I agree there is wear on the motor but remember, there is no smoking, I've got great pick-up, and this problem JUST started. If it was worn engine parts I would think it would have been a gradual coming on of this problem, not an immediate one.
Thougts?


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## SABL (Jul 4, 2008)

Hi again Nb,

Like I said, the first thought is lack of a baffle system that keeps the oil from sloshing out of the sump area. I believe this is also called a "windage tray".... without this piece of sheet-metal your oil will transfer toward the front of the pan and leave the sump (pick-up area) dry and cause loss of pressure. If the oil ain't there the pump has no chance of picking it up. I'm going to stick with my first guess that your mechanic altered or removed some sheet-metal to get the pan reinstalled.... the pump can be pried or knocked off to get the pan off easier. It takes diligence to get everything installed back in proper place... 

The second thought was merely a "FYI" as to another possible cause and does not reflect my actual primary thoughts. I am going with the stated symptom and I truly think you should check for lack of the windage tray as a first step.


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## mack1 (Nov 27, 2007)

Hi guys, 

I figured out what happened to the oil.....the microns eat it up.:grin::grin:

I've never thought that oil wore out, but that it broke down chemically by the burnt gas elements that get by the rings. If the 1 micron filer will get those elements out of the oil, then I guess it should work fine. You didn't say how the micron filter is handled. Is it cleaned ever-so-often or is it replaced? Guess I could go to the link you provided and get all those questions answered. If crude oil prices shoot up high again, I might get interested in that system. 

I have another idea that you might want to look into. The oil pressure falls to zero when you hard stop going forward. How about in reverse? Same thing? Also, those fluctions while going at normal speed. Does that sound like a bad sending unit or bad electrical connection to you? Get someone to fiddle with your wiring while you watch the gauge (engine running of course) and see if you can find a bad or loose connection. 

Try the electrical stuff before you pull the pan, a lot easier to do.

Good to see you back SABL.

Best regards,
Mack1


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## SABL (Jul 4, 2008)

Hey Mack1:wave:

I ,also, am leery about prolonging the life of the engine oil. The filtration system sounds great but what about the additives?? Does the system reduce the added compounds that enhance the oil?? I'm going to stay away from this discussion and change my oil at 3K....along with the filter. Small price compared to the risk. I'm sure the 3 million miles are cumulative, but that has to be factored by the number of buses. It all sounds good but the actual truth is very often stretched to the benefit of the marketer..... I have become cynical in my old age. 

I'm not going to get into this issue and wish Nb the best of luck. Age has taken its toll and it is too late to make changes. I know what works and shy away from certain aspects of "state of the art".... I have been burned before and the scars are everlasting.


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## Nutbuster (Mar 25, 2007)

I hear ya guys! In any event, no Mack I have not tried it in reverse but will do so tonight. The 1 Mic. filter element is replaced every 20K. WHen you first install the system you have to change the media at 10-12K then you go to the 20 to 25K. Pretty easy to do. The media costs about 25 bucks and you'll of course need to add more oil to bring it back to full. I've got a good customer of mine that is an AMSOIL dealer and he is a serious guy when it comes to oil. I mean down to an engineering level of science, way above my head. I introduced him to Mr. Leblanc and he grilled Leblanc over the coals real good and ended up putting the refiners on all of their service trucks. When that guy got sold, that sold me too. SABL I'll check with the shop about the windage tray or baffle system and let you guys know what I find out. bIf it does your hearts any good I didn't come about the refiner system easily as I feel a lot like SABL in my old age as well and the burnt feeling does teach an old dog something... To be extremely careful of snake oil salesmen!


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## SABL (Jul 4, 2008)

Hey Nb,

I didn't mean to sound so harsh in my earlier post....sorry!! I am not having a good day. I will reserve comment for a later date.

I haven't done the calculations on cost effectiveness with the filtration system.... I am at a loss when it comes to brain cells. I burned them up years ago and really don't miss them. What I do have is a penchant for basic auto mechanics...
I'll be back...the kids just showed up.....rare occurance


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## Nutbuster (Mar 25, 2007)

Oh no SABL, I didn't take anything like you were speaking harshly! Sounds like we both grew up in the 70's! Burnt brain cells and all!
The Nut understands!
I'll be in touch with you guys soon. MY service manager is out for a while so I've got to double up and do his job and mine! 
CYA soon!


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## mohitjoshi999 (Jul 24, 2009)

Oil pumps are positive displacement pumps (gear type pumps). Its always covered and full of oil, hard metal gears and housing, very resistant to wear. A very strong foundation for pumping low volumes of oil. There is a spring and ball arrangement that functions as a regulator and all the excess oil that the pump pushes through is releaved by this ball and spring maintaining normal oil pressure. I once had that ball stick closed on a 53 Ford and at idle, it would peg the oil pressure gauge and blew the oil seal at the filter. Those pumps put out a lot of pressure (not a lot of volume) and unless the engine is severly worn out, it will keep normal pressure.


__________________

*crankshaft servicing and lubrication.crankshaft nomenclature and material.Crankshaft working and design.*


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## mack1 (Nov 27, 2007)

Hi mohitjoshi999 and welcome to TSF,

The thread that you were helping was placed here back in February, probably fixed by now. 

Everything you said about the pumps is very true, especially in 53 fords. I also had a 53 ford that stuck the relief valve and it would idle with the gauge pegged out. Mine was a 6 cylinder engine. I've never had that happen on any other vehicle I owned.

Keep up the good work, but try to help new posts:grin:

Very best regards,
Mack1


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