TheSamba.com :: View topic

Thu May 19, 2022 9:17 am

Hey guys,

I dropped off my EJ22 cylinder heads at the machine shop to be decked and I inquired about getting them hot tanked as well, but after reading about how the process can damage the valve seals I decided against it. The motor is from a 97 Legacy with about 125K miles. Was this the right decision? Speaking with the shop this morning and a valve job would have been anywhere from $80-$400 is what the guy said. The decking is only costing me $75, which seemed like a great price.

Thu May 19, 2022 11:22 am

That would be silly to not replace the valve stem seals when the head is out anyway.

Thu May 19, 2022 11:59 am

Opened this topic expecting a camper mod to have hot and cold water on demand.

Nope.

Duncan

Thu May 19, 2022 12:30 pm

DuncanS wrote: Opened this topic expecting a camper mod to have hot and cold water on demand.

Nope.

Duncan

SAME. I was disappointed.

Thu May 19, 2022 12:43 pm

ALIKA T3 wrote: That would be silly to not replace the valve stem seals when the head is out anyway.

x2

Thu May 19, 2022 2:15 pm

ALIKA T3 wrote: That would be silly to not replace the valve stem seals when the head is out anyway.

valvecovergasket wrote: ALIKA T3 wrote: That would be silly to not replace the valve stem seals when the head is out anyway.

x2

Guy said it would be between $80 and $400 for a valve job. What do you reckon is going on with that range? Is it a diy friendly procedure? Ive never torn down a motor to that extent. Also read that the cam gears could rust from the hot tanking process? Really not sure at this point. Replacing just the valve seals wouldn’t really be considered a valve job so that should be on the cheaper end correct?

Thu May 19, 2022 2:59 pm

1. No reputable automotive machine shop would hot tank a cylinder head with all the moving parts in place - - it is ONLY done to a bare casting that is completely disassembled.

2. There is little reason to hot tank an aluminum cylinder head, although it is a faster way (for a production shop) to clean coolant passages in a head or block that is being fully rebuilt. If the heads were subjected to one of those coolant additives designed to stop coolant system leaks, then a hot tank process might be called for. If the coolant passages appear relatively clean, do not worry about hot tanking. Caustic Soda is the main component in hot tank solution and it de-greases and removes rust from coolant (and other) passages in cast iron heads and blocks. On aluminum, it can etch the aluminum if exposure is too long. This is the other reason aluminum heads usually will not be subjected to the hot tank process with caustic soda.

3. Since it is just a cylinder head, if you are concerned that the coolant passages DO need to be cleaned out (rarely is this so), then buy a large container of Drano, heat it up somehow, and dump the Drano and the BARE cylinder head into the kitchen sink (while your wife is away). After an hour or so, you can thoroughly rinse the head. If you use cold Drano, then just let the head soak twice as long. The active ingredient in Drano is sodium hydroxide. I use that shit on everything - - my travel coffee mug included!

4. Valve jobs on multi-valve heads are not cheap. See the factory service manual specification for measuring valve guide wear and use that procedure. If all valves are within specification, then you can inspect the valves and seats for any unusual wear.

5. If there is no unusual wear, then you can use a valve lapping tool and valve grinding paste to lap the valves into the seats. Find a good Youtube video to see how this is done. The disassembly and later re-assembly are fussy, time-consuming work, which you can easily do yourself. The goal in lapping is to restore the metal surfaces on the valve and on the valve seat to a condition in which a good seal is achieved. You need a magnifying glass to check your work. One key takeaway on valve lapping is to be absolutely fastidious about removing all traces of valve grinding paste from the parts of the engine as it will cause damage if left in the engine anywhere.

6. Buy and install OEM-quality valve stem seals. The Subaru dealer can supply them. There are other sources for quality units. There are Youtube videos on Subaru valve stem seal replacement.

7. Kudos to you for re-surfacing the heads. Many DIY-ers will use a whizzy-wheel or similarly inadequate approach to servicing the cylinder head sealing suerface.

8. Get the MLS cylinder head gasket, not the same kind that already failed on you.

Hope this helps!

Thu May 19, 2022 3:30 pm

soda blasting is a great method to clean up aluminum heads... no harmful grit residue like from glass beads. walnut shell is also used.

back in the day, more than one machine shop has ran a 4 bbl carb thru their caustic hot tank overnight to rilly clean it up, only to return to a pile of brass jets in the basket and nothings else! it dissolves aluminum and zinc castings.

Fri May 20, 2022 7:34 am

Howesight wrote: 1. No reputable automotive machine shop would hot tank a cylinder head with all the moving parts in place - - it is ONLY done to a bare casting that is completely disassembled.

2. There is little reason to hot tank an aluminum cylinder head, although it is a faster way (for a production shop) to clean coolant passages in a head or block that is being fully rebuilt. If the heads were subjected to one of those coolant additives designed to stop coolant system leaks, then a hot tank process might be called for. If the coolant passages appear relatively clean, do not worry about hot tanking. Caustic Soda is the main component in hot tank solution and it de-greases and removes rust from coolant (and other) passages in cast iron heads and blocks. On aluminum, it can etch the aluminum if exposure is too long. This is the other reason aluminum heads usually will not be subjected to the hot tank process with caustic soda.

3. Since it is just a cylinder head, if you are concerned that the coolant passages DO need to be cleaned out (rarely is this so), then buy a large container of Drano, heat it up somehow, and dump the Drano and the BARE cylinder head into the kitchen sink (while your wife is away). After an hour or so, you can thoroughly rinse the head. If you use cold Drano, then just let the head soak twice as long. The active ingredient in Drano is sodium hydroxide. I use that shit on everything - - my travel coffee mug included!

4. Valve jobs on multi-valve heads are not cheap. See the factory service manual specification for measuring valve guide wear and use that procedure. If all valves are within specification, then you can inspect the valves and seats for any unusual wear.

5. If there is no unusual wear, then you can use a valve lapping tool and valve grinding paste to lap the valves into the seats. Find a good Youtube video to see how this is done. The disassembly and later re-assembly are fussy, time-consuming work, which you can easily do yourself. The goal in lapping is to restore the metal surfaces on the valve and on the valve seat to a condition in which a good seal is achieved. You need a magnifying glass to check your work. One key takeaway on valve lapping is to be absolutely fastidious about removing all traces of valve grinding paste from the parts of the engine as it will cause damage if left in the engine anywhere.

6. Buy and install OEM-quality valve stem seals. The Subaru dealer can supply them. There are other sources for quality units. There are Youtube videos on Subaru valve stem seal replacement.

7. Kudos to you for re-surfacing the heads. Many DIY-ers will use a whizzy-wheel or similarly inadequate approach to servicing the cylinder head sealing suerface.

8. Get the MLS cylinder head gasket, not the same kind that already failed on you.

Hope this helps!

Excellent info. Thank you! Now you've got me wondering on the quality of the shop though as they suggested they sometimes just do the hot tank with the seals and valves in and it doesn't cause any problems. It is some detergent they use that wouldn't damage the internals according to what he said. Now would it be considered bad form to ask them to show the work is done using a machinist level and gauge keys? How do I make sure the work was done correctly?