Why we use OEM Subaru Genuine water pumps

Wed, 02/11/2015 - 3:34pm - Noah Levy
Non Genuine Pump

At times we get asked why our 105k service costs more than the next shop.  The answer is simple, we use OEM Genuine parts or better....NOT inferior products passed off as OEM.

You see, a lot of folks in this field like to make double margin profits on parts and although that may be nice in the short term, its not always in the best interest of the consumer; you the customer!  These folks like to pass these parts off as OE, which stands for Original Equipment.  The term OEM means Original Equipment Manufacture and doesn't necessarily mean its the same spec component that came with the car (sometimes they also call this OES, Original Equipment Supplier).  You'd think it stops there but it doesn't.  You still have OEM Genuine, which means its the same component that came on the car or would get from Subaru as a factory component.

Lots of companies make water pumps, albeit aftermarket, OE, and OEM but not all water pumps are created equally.  You can physically buy a OEM water pump that orginially produced a product for Subaru but have it be an inferior quality.  This is because Subaru doesn't make water pumps, well they really don't make any of the bolt on components...they contract others and in those contracts they have certain products that are a proprietary design.  The only way to get it is to purchase it directly from a source that sells OEM Genuine components (these will always be in Subaru packaging).

Ok enough of my ramblings....let me show you what I mean.

Here is a 2005 STi, it had a 105k service done elsewhere and as part of the 105k you do the water pump.  The company whom did the work used an aftermarket water pump.  The customer advised he was seeing coolant temps ranging from 195* - 218*, this is concerning because this is at a level of warping heads.  The normal operational temps one should see while driving is typically in the mid 180's to low 190's (under normal cruising conditions for this time of year out here in California), he was seeing 199*+ just cruising.  Being as the radiator fans turn off at 195* this means something isn't right in the system.  A quick test of the cooling system to rule out C0 gases was done (you get C0, or exhaust gas, in the system when you have warped heads).

After ruling out the C0, we moved onto the thermostat and ensuring A) someone installed the right one, as there is a 172* one and 180* one available and B) that its functioning properly.  Both those items checked out so our next level of inspection was at the water pump level.

We know from experience on these aftermarket pumps to check certain areas.  When you look on the surface, it all looks just fine.  But digging deeper into the functionality of the product one can easily point out what is going on.

Here is the aftermarket water pump, it uses the old style cast impeller wheel (like seen on the older non turbo models).


If you look closely, it shows how the profile of the cast impeller doesn’t even follow the inner housing (big gap in front and even on outer leading edge it has a huge gap). 




In this next image it shows (albeit hard to capture) the huge gap associated with the outer leading edge as well.






This is a OEM Genuine unit, it shows the revised stamped steal design but even so, the tolerance should be no different. 




This aftermarket water pump is not engineered properly and it's causing cavitation in the system, leading to poor circulation, and ultimately overheating.

To us as a business, that's not worth the 100% profit margin on the part!


Water pump differences

In relation to the article captured here back in 2011 - http://www.superstreetonline.com/how-to/engine/impp-1103-subaru-ej-series-engine-tech/ They talk about the OEM water pump verse a cast like unit you show here that failed. Now what's interesting is the OEM unit you show now differs a lot as the fins are bent down. My guess is there was a design change at Subaru since then? Could you elaborate more to these changes or what might perceived in the thought basis of this other article? Lastly, is the OEM water pump that is ordered today for an EJ motor now the unit you show? Or does one need to order a particular year model to get that updated OEM pump with the bent fins? (I have a 2004 forester I will be changing out and nearly started looking for the cast turbine pump vs OEM because of what I read. You have got me going back to OEM if this is the case) Thank you for the incite.

LIC Response

All the newer generation turbo cars use the stamped impellers and the only ones I'm aware that still uses the cast is the non turbo cars. The genuine cast impeller is fine, its the aftermarket variants that don't have the correct tolerances for proper flow.

OEM water pump life.

How many miles does a OEM water pump usually last? Have you ever seen one wear out? Should they always be replaced at 105k miles? Thank you for the article. Did you post this up on your facebook page too?

LIC Response

The water pump is due for replacement at 105k on EJ motors. Yes I have seen them prematurely fail (very uncommon) as well as wear out due to not being replaced on interval. We post all our articles on FB as well.

Very good article thanks for

Very good article thanks for sharing.

LIC Response

Our pleasure, thanks for checking it out.

Water pumps...

...and this, ladies and gentlemen, this is why LIC Motorsports does all the work I don't do myself. Honesty and integrity earn my business. That's why I'll drive it past half a dozen "Subaru" shops on my way to have my Subaru services done right, the first time.

LIC Response

Thank you sir!

Great write-up as always

Great write-up as always gentlemen! So 05 STi I replace all oem pulleys and use a new oem tensioner, how do you guys feel about the oem STi pink label timing belt? Seems like a nice oem part. I've always searched for the mythical oem STi gold engine bearings to no avail.

LIC Response

Its a great belt but really nothing overly special about it over a Gates Racing Belt...