Subaru Oil Consumption Problems

Subaru Oil Consumption Repair

ej25 cylinder crosshatch

Subaru 2.5 SOHC cylinder crosshatch @ 200K

Most Subaru owners are aware of the infamous headgasket problem. Along with frequent questions and concerns from customers about Subaru headgasket problems I have also had a lot of oil consumption complaints and concerns from my customers. Over the years of rebuilding and repairing these engines I have noticed a common failure that is consistent with the oil consumption. The piston rings will get stuck in the pistons and stop rotating like they’re designed to, eventually causing oil consumption problems. So, you may think well that’s usually happens with most high mileage motors why is this any different with Subaru’s? This is because the engine is designed in a way where you can fix this problem without disassembly of the lower end. If you have the engine on a stand with the cylinder heads removed you will see large 14mm allen head access plugs and an access plate also know as the PCV baffle plate. With the plugs removed you can also remove one side of the wrist pin clip and knock out the pin with a long ¼ extension. Now the piston can be easily removed and either replace the rings or clean and free them up if possible. The way the block is designed you cannot hone the cylinder bores but I have had good success with the rings seating without doing re-hone on the cylinder walls. Also, when this is performed there is also a significant increase in engine power due to the compression that has been restored. Even 200K engines that I have done headgaskets on still have good crosshatch in the cylinder walls so I have pretty good confidence when performing this service. You should always pay close attention to the condition of the engine by listening to it before you go this far into a repair. You would not be happy to do all this and have a rod bearing go out later. Every situation is different, just make sure the engine sounds healthy before going this far because it wouldn’t be much more to put new rod and main bearings in there also.

access hole with piston

access hole with piston down where you can see wrist pin clips

access hole no piston

access hole with piston pushed down so you can see through the block

Subaru Engine Noise

Now, since we’re on the subject of engine noise Subaru engines also have a common problem of the pistons slapping around in the cylinders. This is known as “piston slap” and is common on any engine that has such short pistons. The piston skirts will taper overtime from the continuous expansion and contraction of metal caused by heat. This problem has even been recognized by S.O.A and they have service bulletins for them. I am not completely sure of what is stated in the bulletin but I do know how to differentiate the problems. Piston slap noise would be hard to explain in text, you would just have to recognize it from experience. The noise will decrease or go away as the engine warms up, a rod bearing would be more consistent and if you kill/disable the cylinder with the bad rod bearing it should quite up some but not always.

ej25 crankshaft journal

crankshaft journal of Subaru 2.5 with noisy rod bearing, crankshaft good, can be polished.

With all this being said I have had huge success with replacing headgaskets, servicing the valve train and new piston rings for the engine. If the crankshaft is good, a complete rebuild (new rod and main bearings) is also great but from experience if the crankshaft is damaged just get a new short block from Subaru. It’s not worth the money and time if the crankshaft has been damaged; they just never seem to be the same after that. Look at the pictures below, both failed rod bearings never damaged the crankshaft. As long as it doesn’t get too hot or completely wear the bearing to a point that the rod is slamming on the crank journal, the crankshaft can be saved. Measure the journal and have it polished with a leather belt on a lathe (just send it to a machine shop).

ej25 failed rod bearing 2

another failed rod bearing ej25 160K

This post was written by: Martin Hand

Donations

If you find this information helpful please consider a donation. These articles, questions and comments are very time consuming so even a small donation gives me motivation to keep educating automotive owners. Donations will allow us to continue open questioning/comments, automotive education and repair tutorials in the future as the business grows. All proceeds go to the expansion and maintenance mdhmotors.com. Thank You



Martin Hand

About Martin Hand

ASE Certified L1 Advanced Mastertech. Martin Hand has over 15 years experience in Asian and European Import Auto Repair. Specializing in electrical diagnosis, engine performance, AT/MT transmission repair/rebuild. Martin is also pursuing a degree in Computers Science & Information Systems starting at Portland Community College while he plans to transfer to OIT. Certified in Java application level programming, experienced with other languages such as PHP, Ruby, JavaScript and Swift. Martin has future plans of automotive diagnostic software development.

Leave a Reply

Your email address will not be published. Required fields are marked *