ddq

My 2.5L Vcg Replacement

23 posts in this topic

This is my write up of the valve cover gasket change on a 2000 626 with the 2.5L. Hopefully this wiill help somebody in the future.

The front VCG swap was as simple as removing the spark plug caps and valve cover bolts. Remember to clean the cover where the old gasket was. There will be pieces of gasket stuck to the cover and the motor. I found the best way to remove the old gasket was a small flat head screw drver.

leaky cover

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http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1528.jpg

Id recommend putting the bolts in order so that you dont put the short ones in where the long ones go, and vise versa.

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http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1531.jpg

Old gasket hard and brittle

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http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1535.jpg

Be careful not to over tighten the bolts when putting the cover back on.

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Rear gasket:

Start with removing the spark plug caps. I labelled them to keep them in order. Also, unplug everything that looks light it is attached to the intake manifold. I used a permenant marker and wrote letters on both sides of the plugs so that I could match them back up later.

http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1541.jpg

This part of the intake will also need to be removed from the IM. There are two nuts and two bolts attaching it.

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http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1548.jpg

Unplug all the vacuum lines and fuel lines. Be careful detaching this fuel line because there are two small washers that can easily be lost if they fall down into the motor compartment.

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http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1550.jpg

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When you think you have everything unplugged check again. There will be a small vacuum hose or electrical plug still connected. There are a few plugs and hoses between the IM and firewall that are hard to get to. Once everything is unplugged, unbolt the IM. There is a hidden bolt between the IM and firewall. I had no problem removing it or putting it back in but it is hard to see. My wrench is on it here:

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http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1552.jpg

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http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1557.jpg

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When this bolt is out CAREFULLY pick the IM up and set it on a flat surface like the ground. DO NOT set it back down somewhere else in the motor bay. You will break the fragile vacuum line that is attached to the underside of the manifold. If you have to set it back down, set it exactly where it was.

There were two plugs between the IM and frewall on the passenger side that I couldnt see until I tried to remove the manifold. Here they are, and here is what you should NOT do. I set the manifold down and something broke the vacuum hose underneith it.

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http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1561.jpg

Here are the vacuum canisters and the broken canister/hose:

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http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1571.jpg

Rather than buying new ones, I made some new canisters out of metal fuel filters. I mounted them outside the manifold and they work great.

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http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1578.jpg

When the manifold is off, remove thevalve cover bolts and swap the gasket just like you did with the front gasket. CAREFULLY put the manifold back into place and plug everything back in. It took me about all day to do both gaskets, but I also took pictures and had to fabricate the canisters. If you dont break anything, you can probably do both gaskets in 3 hours if you take your time.

Again, I recommend you label everything so all bolts and nuts are accounted for when its time to put it back together.

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http://i130.photobucket.com/albums/p275/nissan11/Mazda/IMG_1569-1.jpg

I hope this will be some help to someone.

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This is a nice write-up; the only thing I would add is that the torque spec for the VCG bolts is 45-70 INCH-pounds...this is like screwdriver tight. Be very careful not to overtighten, as the bolts will snap off inside the head.

I've also found that I periodically need to retighten these bolts, as the gaskets squish over time, and the bolts work themselves loose.

Edited by snailman153624
The torque spec I originally stated was incorrect. The post has been updated to reflect the correct value.

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nice write up!!

and ya, you need to tighten the VC bolt to the right specs. i did my front a while back and broke 2 bolts cuz i over tightened them. so i had to go to lowe's and get replacement ones, then i decided to replace all of them. the new bolt can handle the high torque and i didn't need to re-tighten them after the gasket gets softer. i think they fit 6mm holes (10mm head) and were 1.5" long. i didn't replace the longest ones cuz they didn't break. but now good thing i got myself a torque wrench. they will come in handy when i need to do other jobs.

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i didn't tighten them too much. and i know the head can get damaged and deformed from over-tightening them. i still have 3 of the original bolts (the long ones) in there and all of them are tightened to about the same torque spec. so if the big bolts break, then i know they are too tight and so far they are still in tact.

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One other thing I forgot to mention. If you get your gaskets from the auto parts store, open the box and look at them before you leave. I bought a set of gaskets, drove home, pulled off the front valve cover and discovered that I had two rear gaskets, not a front and a rear. Luckily, I had another vehicle to drive back to the store and exchange the kit for another.

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Hi I'm a newbie to this site. Great info, especially for the novice. Was just preparing to think about considering replacing my vcg's in a 2002 626 2.5L. Thanks for taking the time to post this and take pictures. A couple of questions. Did you drain the coolant before starting? And while you had the IM off did you replace the gaskets and the coolant transfer pipe hose?

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Hi I'm a newbie to this site. Great info, especially for the novice. Was just preparing to think about considering replacing my vcg's in a 2002 626 2.5L. Thanks for taking the time to post this and take pictures. A couple of questions. Did you drain the coolant before starting? And while you had the IM off did you replace the gaskets and the coolant transfer pipe hose?

I've never touched the coolant transfer pipe hose on any of our cars, and I've owned a lot of these V6 motors...and never had one leak, ever [knocks on wood].

There's no need to drain the coolant; the only coolant hoses you disconnect go to the throttle body, and these are higher up than the rest of the cooling system, so just plug them with a piece of shop towel and you won't lose much if any.

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Some changes on the intake manifold were made in between the 1996 and 2000 models because my intake isn't the same and some bolts aren't at the same place. I was almost able to take it off but a few lines, and maybe 1 o 2 more bolts were holding back near the IM... I couldn't find them and i was afraid that i'd catch rain. En top of that, one of my spark plug is broken, so i'm running on 5 cylinders right now...

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This is a nice write-up; the only thing I would add is that the torque spec for the VCG bolts is 18-20 INCH-pounds...I've also found that I periodically need to retighten these bolts, as the gaskets squish over time, and the bolts work themselves loose.

Hey Snailman,

It seemed to me that 18 to 20 inch-pounds sounded a little "light," so I called Momentum Mazda of Gastonia, NC. The mechanic I spoke with, David, looked up the VC torque specs and said the range is actually 44 to 78 inch-pounds.

Just to be sure about the VC torque specs, I then called Robert at my local Ford dealership, and asked him what the VC torque specs were for a '95 Ford Probe V6. Robert said that according to AllData, the VC torque range is 45 to 70 inch-pounds, which is pretty much in line with what David from the Mazda dealership told me.

Snailman, if you don't mind my asking, what source did you use to get your torque specs from?

Cordially,

eloqutus

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Thanks for this post - it was very useful.

So I found where the funny interior smells were coming from...

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Oh yeah that bugger was definitely leaking through the VCG and burning on the heatshield. Bet that made a nice burnt oil smell. Good pics.

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Info came in handy. First replaced the front and back valve cover gaskets on my 98 626 in 2008. The back started leaking again in Feb of 2012, around the same time my car started to run really rough. I had forgotten in order to simply tighten the bolts the IM had to be removed. What a headache and backache. But it beats paying someone hundreds of dollars to do it. Also it is a good idea to loosen the gas cap to relieve pressure so less fuel will leak when the fuel line is taken off.

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I used a premium silicone gasket kit so I hope it lasts longer than the 4 years yours did MAN39ER. I guess the regular black gaskets turn into stiff brittle plastic after awhile.

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Was attempting to put on the IM. A ground wire? with a white plastic tab on the end pulled loose near the firewall. Can't find where it goes. Anyone have any ideal?

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Is it absolutely necessary to have a torque wrench? Or can I just be really careful not to over tighten each pass I make tightening them back up?

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