Oil Pump, new style versus old style,

JayArr

Original poster
Member
Sep 24, 2018
504
Mission BC Canada
Hi All

I'm swapping in an engine I bought from the wrecker for an engine that blew the head gasket and warped the head.

The vehicle is a 2005 Envoy XL LL8 (inline 6) and the new engine is from a 2003 Trailblazer. The engines were identical until today.

I noticed on Rock Auto that the rebuild kits for oil pumps refered to a "second design"

When I pulled both of my engines apart I see a difference and I'm inclined to assume that the picture with the blue O-ring is the second design while the picture with the orange washer was the original design.

Can someone confirm this to be true?

Next question... when did the second design come out? Is finding it in an 03 a sign that someone has worked on this engine before me?

JayArr
 

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Mike534x

Member
Apr 9, 2012
894
That is interesting....I wonder why the pick up tube (?) on the second one is shorter. Maybe @MRRSM can help shed some light?
 
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Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
AFAIK, The flat face design is the newest one. My 02 with the 03 engine had the old O-ring design. Why it was changed is unknown since the LS engines continued to use the O-ring. I think there were some reports of leakage on the early engines due to improper assembly and damaged O-rings.

Since you took it apart, you should put a new O-ring.
 

mrrsm

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Oct 22, 2015
7,639
Tampa Bay Area
+1 ---^--- ...The distinctions between the Old Front Cover and New Front Cover (Both having the Gerotor Oil Pumps Screw-Head Bolted to the inside lower portions of the Covers) are significant. In this first series of images ...you can read the installation instructions that make the comparison of the two designs very well… and for good reasons:

(1) The Original (OLD) Style Gerotor Pump used a very shallow insert tube portion of the Oil Pickup Tube and also employed a Blue PTFE Sealing “O” Ring mating to the shallow, submerged “O” Ring Groove in the Base of the Gerotor Oil Pump to establish a vacuum seal.

(2) The problem however with the Early Model TBs and Envoy LL8s sporting the OLD Oil Pump/Oil Pick Up Tube Design of their mate ups areas was that in some cases… Air Cavitation occurred due to the Blue “O” Ring either getting nicked or cut during the factory OEM Assembly and later flattening out and allowing for a serious loss of suction leading to an inability of the Gerotor Oil Pump Gears to vacuum Crankcase Oil up inside of the Gerotor Gears and provide constant Oil Pressure.

(3) The solution GM worked out was to completely re-design the NEW Oil Pump Pick-Up Tube interface to include expanding the side of the mating flange surfaces meeting up at the bottom of the Gerotor Oil Pump Tube Manifold and eliminate the Submerged “O” Ring Groove and Blue “O”Ring entirely in favor of having a Longer Insert Extension Depth on the Tube penetrating much deeper inside of the GOP Manifold.

(4) And instead of using that Blue "O" Ring... GM opted to use a full-face Orange Teflon Coated Sealing Grommet Style Washer in the NEW Design ...behaving almost like a Ribbed, Water-Proof “Metri-pack” design to guarantee no loss of suction from around and in between the Deeper Set Oil Pick Up Tube and the inner workings of the Gerotor Oil Pump Gears. These Two Different Pumps and Pick-Up Tubes are NOT inter-changeable.

These are the Old to New Comparison Images and Install Instructions from my Photobucket:

http://s557.photobucket.com/user/60...AZERENGINEREPAIR/GEROTOROILPUMP?sort=3&page=1

...and the New Design as shown in my “Flickr” Bucket:

https://www.flickr.com/photos/12611.../126111508@N07/albums/72157671179967478/page2

And if you need to research other New Parts and Pieces for your Re-Build… this link to my other images has a lot of data showing the parts I purchased along with their Make-Model-Part Numbers and Box Ends-Packaging Imagery for information on what to use during a Complete Engine Re-Build of the GM 4.2L LL8 Engine:

https://www.flickr.com/photos/126111508@N07/albums/72157671179967478/with/43350771592/

42494505745_234ac7eabe_z.jpg42494505965_d4f791ba11_z.jpg42681914194_3fd6b6dc60_z.jpg43350770822_f24af5ce29_z.jpg42494505865_f069e40fc8_z.jpg42681914204_08d9ca7d8e_z.jpg43350752342_de8cf5f26a_z.jpg43350770632_56bd86ecbc_z.jpg43350779592_1324cba187_z.jpg
 
Last edited:

Sparky

Member
Dec 4, 2011
12,927
It is funny because the LS engines continued using the O ring setup. My 07 Silverado has the O ring, and it did flatten and compress over time, starting to let it suck some air (particularly when the oil was cold), causing lower cold start oil pressure, some rather bad valvetrain noise, etc. I replaced that O ring this past spring and I almost never have cold start ticking anymore.
 

cornchip

Member
Jan 6, 2013
637
I would have never used a single bolt to secure the pickup tube. That's why I look at the second design as somewhat inferior. You'll never fully achieve full clamping pressure without two bolts opposite of center. Could have been a third design.
 
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Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Both first and second design use a single bolt. On LS engines, the pump does have two bolt holes but only one is used, the one that's not accessible with the oil pan in place. This second hole is used as a hack to allow pickup tube re-installation without having to pull the oil pan. There is a kit available to add a second hold down on the LS.
 

JayArr

Original poster
Member
Sep 24, 2018
504
Mission BC Canada
Thanks for all the replies guys, if I had guessed I would have thought the blue O-ring model was the newer one, good thing I asked. I'll clean up the orange model pump and swap it into the 03 engine. Luckily I just got a case of Berkbile 2+2 Gum Cutter to get rid of all that varnish.
 

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