Jump to content
Ultimate Subaru Message Board

Cleaning cyclinder block, head, camshaft etc

Recommended Posts

I have the 2.5 liter DOHC engine with 86K miles out on stand. Have removed timing belt, camshafts, head to get to blown head gasket. Never done this before, so I am learning.


I have a few questions:


1. What should I look for visually in the cyclinder bore and pistons to tell the health of the short block.

2. I see carbon rings at the top of cyclinder bore. How should I clean up this and piston exterior? What's a no-no? For example, can I use just a regular engine degreaser? Should any degreaser be rinsed with water or is that a no-no? Can piston top surface be rinsed with water.

3. I have dust/sand etc still on the exterior of the engine block (I didn't wash it down before removing the head). If these fall into cyclinder, is there a good way of removing. Or should I hose down the dust/sand with water first - what if water hits the pistons etc

4. How should I clean the head? Specially the side where valves sit. Is water a no-no? Should I squirt something into intake/exhaust manifold to clean carbon deposits there?

5. What about the front of the engine - where timing belt goes. Should I clean the front surface with something. Is water rinsing a no-no?

6. Is wire brush a good idea?

7. Is cleaning the threaded block holes for head bolts required - Hayes manual recommends doing it with a tap.

8. What about cleaning oil/coolant passages? Is that required?

Share this post

Link to post
Share on other sites

1. There should be crosshatch still visible, with no scratches going up and down the length of the cylinder. There should be no/almost no ring groove at the top of the cylinder.

2.I would scrape the carbon ring off with a razor blade. Same with piston face, just bring it to TDC. try not to get this stuff all over the cylinder walls.

3. I would just try not to get it everywhere. If it lands in a cylinder, wipe it out with a clean rag. Keep rags in the cylinders to block things from falling in there.

4. Since you are replacing a head gasket, I'd send the head to a machine shop and have it checked to make sure it is flat. They can disassemble the head and soak it in a solution which will get all the crud off of it. m They can do a valve job too, if you desire.

5. Simple green or another strong solution that won't etch aluminum can be used. You can rinse with water if you dont get it anywhere but on the outside of the engine.

6. I don't see why not. Just dont clean the block/head mating surfaces with it.

7. I don't know where you are going to find the tp, but if you can get ahold of one, i'd do it. Insurance and all.

8. In the head? Let the machine shop clean the head, inside and out. If you choose to do it, I'd use brake cleaner, then compressed air.

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now