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| mrfunji
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| Posted:Apr 12 2003, 06:21 AM |
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Rebuilding Head
Hopefully, this will be a helpful guide for anyone that wants to rebuild their head. It should add some more indepth and detailed photos than the mazda/haynes manual. Enjoy!
For those wondering, I did this 20,000 miles ago, which is why my head is so shiney. Suddenly, I started using LOTS of oil and my #4 plug was very dirty. Suspecting a valve seal (because of the fast oil usage), I took the head off to conduct an investigation....
I'd recommend a good set of tools, some mechanical ability, and a CLEAN work environment. If it's not clean, you might end up doing this again in the near future.
This head is off an F2 out of a 1991 Mazda 626 LX. This is the same head used from 1988 to 1992 on Mazda 626 and MX6 models DX, LX and GT. Also, anyone overseas with a 12 valve 2.2L motor, this is probably your head as well.
The most commonly used tools are (for rebuilding the head):
- 3/8" drive
- 12 mm - 14 mm sockets
- 3" extension |
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| Posted:Apr 12 2003, 06:22 AM |
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Starting
We start with the head. First step is to take the rocker arm off. This can be done with the head in or out of the car, and gives access to the HLAs and camshaft. Make sure the #1 is pointing up on the cam gear, and lightly loosen the rocker arm retaining bolts in the order listed in the picture, then loosen them completely in the same order.
NOTE: These bolts also hold down the cam bearing caps. The cam beraring caps MUST be kept in order so they are re-installed in their orginal place with the oil seals lined up.
NOTE: Keep these bolts and spacers paired together and store them in labeled plastic baggies so they can be reinstalled in the same place.
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| Posted:Apr 12 2003, 06:23 AM |
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Rocker Arms Unbolted
NOTE: Be careful of stuff sliding off. If it does, they HAVE to go back in the original order.
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| Posted:Apr 12 2003, 06:25 AM |
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Rocker Arms
Again, be careful to keep the components in the original order.
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| Posted:Apr 12 2003, 06:25 AM |
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HLA Unit
If you need to service the HLAs, they are on the underside of the rocker arm. They can be pulled out by hand.
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| Posted:Apr 12 2003, 06:26 AM |
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Head without rocker arms
Head with the rocker arms taken off. The cam shaft is now accessible by removing the 5 bearing caps (2 ends, 3 middle pictured here).
NOTE: The 3 middle ones MUST be kept in order, and the oiling hole in the middle cap MUST be installed in that position (hole on the intake side)
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| Posted:Apr 12 2003, 06:27 AM |
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Head with camshaft exposed
Here is the head with the camshaft exposed. It can now be removed (with the head in or out of the car). Now is a good time to inspect the cam for damage.
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| Posted:Apr 12 2003, 06:28 AM |
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Scored Cam
By visual inspection, I can see that my cam is scored. This area is the part that sits in the pillow bearing. Compare it's surface to the cam lobes to the right and left and note the difference in smoothness. This is bad, and I'm going to have to get the cam resurfaced or replaced if the scoring is too deep. However, this is not the cause of my problem. The scoring was probably due to sand or some foreign object (which is why a CLEAN work environment is a good idea). It might not look that bad in the picture but it is (by feeling it).
To completely remove the cam, unbolt the sprocket (probably need an air ratchet or strong hands), unbolt the front bearing cap and lift out the cam. It's pretty straight forward.
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| Posted:Apr 12 2003, 06:29 AM |
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Removing Valve Springs
The next step is to remove the valve components. This should only be done with the head OFF THE CAR, due to the danger of valves falling down into the combustion chamber. To start, we need to obtain a valve spring compressor. The one I have I got from autozone for about $20.
The bottom hooks grab the spring, and the middle part touches the top. As you twist the handle, the spring compresses, and in theory the retainers fall out.
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| Posted:Apr 12 2003, 06:30 AM |
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The "tap" trick
After many failed attempts to remove the spring, a contact at a machine shop suggested tapping the top of the spring with a hammer before compressing. This upsets the valve spring retainers and lets them free. Low and behold, it worked!!
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| Posted:Apr 12 2003, 06:31 AM |
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Compressing the spring
You should attach the valve spring compressor as far down the spring as possible. However, because the hooks are so large, the gaps in the spring get too small, so the compressor can only hook in right around the middle.
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| Posted:Apr 12 2003, 06:32 AM |
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Uncompress
Take the spring off and SLOWLY uncompress the spring. THERE IS A LOT OF ENERGY STORED SO BE CAREFUL!!!! It can shoot a hole in your ceiling. Be careful not to lose any valve components
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| Posted:Apr 12 2003, 06:33 AM |
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Storing
VERY IMPORTANT: The parts pictured below are from the #4 exhaust valve. The parts are in a plastic bag and CANNOT MIX with any other parts. This way, all the same parts go back in the same place. That is VERY important. Remember, there are 2 intake valves per cylinder.
You should have a valve, a spring, the top washer, two retainers, and a bottom silver washer (not pictured). Make sure you have all the parts in the bag and put away BEFORE you start on the next valve, or you'll probably get them confused.
This process is repeated again for each valve. This leaves the valve stem seals exposed.
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| Posted:Apr 12 2003, 06:34 AM |
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Valve Stem Seals
After a short visual inspection, my assumptions were correct.
Obviously, you can tell the difference between a good valve stem seal (left) and a bad one (right).
I actually found this quite humorous despite all the work it took to get to it. It was in TERRIBLE shape for something with 20,000 miles on it.
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| Posted:Apr 12 2003, 06:35 AM |
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Broken Seal
Here are the parts of the seal that separated from the rest of it. This rubber ring is supposed to seal around the valve stem to prevent oil from going into the combustion chamber. Obviously, it wasn't doing it's job. I have NO IDEA what caused this.
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| Posted:Apr 12 2003, 06:36 AM |
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Removing the seals
These valve seals are a pain to get off. You need plyers to get them off and they CANNOT BE REUSED. They require just as much effort to pull off as they do to press on. As you can see, the top rubber part and the bottom metal part have completely separated from eachother. Hopefully this will not happen again in another 20,000 miles. Repeat this step for the other valve stem seals.
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