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EA82 - no compression in one cylinder


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32 replies to this topic

#26 Dee2

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Posted 04 September 2017 - 02:08 PM

I'd like to get to the bottom of why the valve broke in the first place. Any thoughts?

 

Google "what causes burned valves".

 

There are many things that can lead to a burnt valve.  You should look into reasons why only one cylinder has the problem.



#27 Subaru Scott

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Posted 04 September 2017 - 10:13 PM

Yes, burnt, not broken. 

 

This can happen from just a small defect in either the valve or seat. Once there is a pathway made for combustion pressure to get through, it will cut the metal away just like a torch. 



#28 jasonkaye

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Posted 09 September 2017 - 03:26 PM

As I'm waiting for the heads to come back from the machine shop, I've been waffling over how deep to go. I removed the heads with the engine still in the vehicle.

 

In order to check the piston rings, I need to pull the engine. And if I'm pulling the engine and checking/replacing the rings, I might as well split the block and check/replace the main bearings. And while the engine's out, well let's replace the clutch, too. You get my drift - how far down the rabbit hole do I go?

 

Considering this is my daily driver, and I'm stressed out finding rides to and from work, part of me is leaning toward the quicker option: put the refurbished heads on and get the car running.

 

Of course, another part of me is saying, "Hey you're this deep already, might as well go for a complete rebuild."

 

Any wise advice from the forum?

 

Jason



#29 jasonkaye

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Posted 09 September 2017 - 05:52 PM

Reading more through the forums, there seems to be a strong preference for retiring the EA82. This leads me to think I'll just put the refurbished heads on, get this vehicle running in the short term, and in the medium- to long-term look into the EJ22 swap.

 

What do you think?



#30 DaveT

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Posted 09 September 2017 - 06:08 PM

Unless you have serious suspicion about the lower end, put the heads on it.

I avoid the long down time problem by refurbishing a spare engine, then just do the swap on a weekend.

#31 djellum

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Posted 10 September 2017 - 03:41 AM

If the blocks in good enough shape you could put new rings in without splitting the case. There are ports to let you pull the wrist pins. Whether or not it will work depends on the cross hatch in the cylinders. Would need to pull the motor for that but its super easy on these

#32 GeneralDisorder

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Posted 11 September 2017 - 09:38 PM

Burnt exhaust valves are due to piston ring oil control failure. The carbon builds up around the valve stem, and prevents the valve from closing rapidly and completely. It also coats the valve seat and face. The valve has 1000+ degree exhaust gasses traveling over it and if it cannot make complete and rapid contact with the seat, it cannot dissipate this heat into the cylinder head. This heat soaks into the stem and carbonizes more oil to the stem and guide making the problem worse and worse.

If you don't replace the rings, it's a GUARANTEE the burnt valve situation will reappear within 20k miles.

Before you go any deeper into this foolish rabbit hole - pull the oil pump and check it's condition. If it's scored up inside just wash your hands of the engine, or more likely the whole car. You can't buy oil pumps anymore for this engine.

GD

Edited by GeneralDisorder, 11 September 2017 - 09:39 PM.


#33 jasonkaye

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Posted 17 September 2017 - 04:54 PM

I had already pulled the oil pump to replace it with one from a parts car. Both oil pumps look to be in good shape, and it'll get new seals of course.

 

I pulled the pistons and cleaned them up.

 

For new piston rings, I can get a set from Subaru for $180 or RockAuto (brand "Sealed Power") for $25. I'm a bit surprised by both prices - do you all have a suggestion on which set to buy?






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