Hello Mazda Owners,

First, I want to thank everyone for their participation in this forum. There is a wealth of knowledge and experience here. Secondly, I want to ask if anyone can help me with a problem that I am having with my '95 Millenia.

The car just recently, yesterday, began missing and running rough...it misses mostly at idle, engine hesitates on acceleration (but not if I floor it hard) and has a general loss of engine power. I did a little checking under the hood. I started with the spark plug wires. As I pulled the first plug wire out of the plug recepticle, I notice that engine oil has filled the bottom of the recepticle and the spark plug and spark plug boot is covered with engine oil. All of the rest of the plug recepticles are bone dry. The the spark plug recepticle that has oil in it is located on the top of the engine, and I believe it is the back cylinder (because it is fartherest from the timing belt area on the front of the engine and fatherest from the passenger side of the car.). Also, it is a 6 cylinder engine. I believe this oil leak is what is causing the plug to not fire, thus the missing, rough idle and loss of power.

Can someone PLEASE help me?? Does anyone know what the problem is based on the above description I have provided? And would you have any suggestions as to how to fix it?? I would be greatly appreciative for your help!!!! Thank You Verrry Much!!

Wavy

Sounds like a leaking valve cover gasket. No big deal to replace one, but clean all oil off the mating surfaces and use a silicone gasket sealer when you reassemble. Do not overtighten, as this can contribute to leaks.

Well, I agree with the above post to a point. It is not a simple job to replace the valve cover gaskets on the 2.5 liter V6. I just replaced both valve gaskets in my 99 Mazda 626 V6 and to replace the rear head valve cover gasket, you must first remove the intake manifold. This is a very unpleasant job, because Mazda decided to attach the engine wiring harness to the manifold. Front head valve cover gasket is readily accessible, but removal of the intake manifold takes some time and patience.

Here are the parts you need to replace the valve cover gaskets in a 2.5 liter V6:

1. valve cover gaskets for both heads - they are different for the front and rear heads.

2. sealing washers: 18 short ones and 5 long ones are required. These go under the valve cover bolts

3. intake manifold gaskets (2)

4. fuel rail banjo fitting copper sealing washers (2)

5. high temperature silicone sealant (Permatex, 600 deg F)

The intake manifold is easiest to remove as a unit along with the throttle body and fuel injector rail. If you detach the throttle body from the manifold, you must replace additional gasket between the manifold and the throttle body. Disconnect the negative battery terminal before starting the manifold removal. To make the job easier it is advisable to unplug most of the wiring harness connectors and vacuum lines. You need to label these for proper reinstallation. I did this by affixing a small piece of masking tape with a letter on it (e.g. A with a corresponding A for the item that the connector plugs into. I went all the way to letter W, which gives you an idea how many connectors and vacuum lines you need to unplug). Removal of the short fuel line from the fuel regulator proved very difficult, so I slit the line and replaced with a new one (better than breaking the regulator inlet pipe). In addition to the visible bolts, there is a bracket at the very back of the intake manifold that you must remove to get the manifold off.

If you have a shop manual for the 2.5 liter V6, there are several areas where you need to apply small amount of silicone sealant before you installt he new valve cover gaskets. It is important to do so, otherwise the gaskets may leak. You also must replace the sealing washers, otherwise there may be oil leaks. The gaskets fit neatly into the grooves on each valve cover, so you need not worry about misaligning the gaskets.

The bad part is that the cost of Mazda parts is ridiculous. Each gasket retails for about $ 31, each sealing washer for $ 6.80 for 5 long ones, and $ 3.80 a piece for 18 short ones. The manifold gaskets are about $ 10 a piece. I checked with Discount Auto parts and they sell a gasket replacement kit which includes both valve cover gaskets and sealing washers for about $ 80. You will still need intake manifold gaskets, and 2 banjo fuel fitting sealing washers ($1.20 a p[iece and nobody else but Mazda has them and they had to order them!) .

Some others cautions:

1. When installing the intake manifold gaskets, make sure the convex side of the gasket is facing toward the manifold.

2. When reinstalling the fuel rail fitting banjo bolt, first loosen the fuel line mount bolts; otherwise the bolt is hard to start and you may cross thread it! Once you loosen the fuel line mount bolts (2 of them and very difficult to get to), the banjo filling will line up properly and the bolt will go in easily by hand.

3. Torque the intake manifold bolts sequentially to specified torque in several steps. Do not overtorque! The specified torque is 14 to 18 ft-lbs.

4. Torque the valve cover bolts to spec in several steps, the recommended torque on those is 45 to 70 inch-lbs (that's inch-lbs, not ft-lbs: 1 ft-lbs =12 inch-lbs). Do not overtorque these bolts, or you will distort the valve covers.

5. Make sure you reconnect every electrical harness connector and every vacuum line corectly.

6. Be careful when removing the electrical harness attachment clips from the manifold as they are fragile and break easily.

Replacing the valve cover gaskets at a Mazda dealer is a multi- hundred dollar job, as parts alone are well over $ 100 and there is at least 2 or three hours labor required.

If you decide to let an independent shop do the work, make sure they replace the sealing washers and intake manifold gaskets, as well as the fuel banjo fitting washers. I hope this helps. I have no oil leaks so I must have done the job right.

there ought to be little "o" shaped gaskets that are under the VC that go around the spark plug wells. getting a gasket set would be a good idea as you're going to have to replace the whole thing anyway after removing the assy.

The O shaped gaskets around the plugs wells are part of each valve cover gasket.