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i called Mazda today about replacing my valve seals, and they said that if you jsut do your valve seals, it will "blow oil through your entire engine"... and that to really make everything proper they would have to do a full rebuild on the engine.. is their any truth to this, this doesnt sound right at all to me..

It happened to my mazda B2200! The clutch fan went bad & my head gasket popped. So I redid the whole head with a kit including valve seals. Worked great for about a day, then started smoking bad from oil burning by the rings. Different series engine, but yes it did happen on a mazda.

well shat if thats the case i'll just put my escort motor in. lol. I just dont understand the logic of putting something better in the car and it makes things worse?

It depends on the condition of the rest of the parts in the engine. If you replace these and increase oil pressure by doing so, another part that is on its last legs might let go causing another problem.

I had a professional rebuild on a head only to find after reassembly, that my rings were worn out and had to redo the bottom end.

It's better and cheaper to do it right the 1st time, your car will be more reliable too.

my car just turned over 200,000km, doesnt burn oil (except for when I start it after 6-7 hours of sitting hense the valve seals) I don't know if this would need a full rebuild. It runs and drives fine.. I guess it all depends on how it was driven over its whole life. But still, I mean its not like its tired, I think its just from sitting around so much. Just doing the valve seals, not rebuilding the head like you did, shouldnt make a huge difference should it?

Altthough it's not a Mazda, it hold true on my sister's Prelude. A few months after getting the car her timing belt snapped. Because it's an interference motor, she bent most of the valves. Most places recommended putting in a new motor for exactly that reason, but they wanted over $2000 for an H23 alone. They decided to just rebuild the head since the bottom end looked mint. Over the course of a few years, it started to burn more and more oil, but it seems to make sence, as weird as it is to believe.

I have to question this. The valve STEM SEALS are not a high pressure seal. They prevent the bulk of oil in contact with the top of the valve train from draining into the combustion chamber throught the valve guide. They are designed to allow a small amount of oil to pass and lubricate the valve stem in the guide. I have changed dried out valve stem seals on many an engine that sat for a couple years unused. In my experience this is just good practice.

If you're talking about replacing valve SEATS with a new seat or even a new grind I could see that maybe worn rings could become a problem where they weren't in the past because the valves would seal against combustion better than they had been. In that case you may see blow-by and excessive crankcase pressure but honestly even at that, I would be surpised unless I knew that the engine was high mileage and was already burning some oil.

I'm not saying it's not possible and maybe the Mazda guy really believes that this is the case, but I've done several partial rebuilds on engines that I knew were otherwise healthy without issue.

wytbishop wrote:I have to question this. The valve STEM SEALS are not a high pressure seal. They prevent the bulk of oil in contact with the top of the valve train from draining into the combustion chamber throught the valve guide. They are designed to allow a small amount of oil to pass and lubricate the valve stem in the guide. I have changed dried out valve stem seals on many an engine that sat for a couple years unused. In my experience this is just good practice.

If you're talking about replacing valve SEATS with a new seat or even a new grind I could see that maybe worn rings could become a problem where they weren't in the past because the valves would seal against combustion better than they had been. In that case you may see blow-by and excessive crankcase pressure but honestly even at that, I would be surpised unless I knew that the engine was high mileage and was already burning some oil.

I'm not saying it's not possible and maybe the Mazda guy really believes that this is the case, but I've done several partial rebuilds on engines that I knew were otherwise healthy without issue.

Thats what I mean, peope here are talking about rebuilding heads, valvetrain, etc.. but all I want to do is change the seal. The same valves, remain, everything else, except the seal isnt worn out anymore. The pressure cant be that great that it would do this.. I think they are just trying to upsell.

if combustion pressure is reaching the valve stem seals, you have bigger problems than burning some oil on startup.

130k miles roughly... yeah you need rings/waterpump/& timing belt.

lost_mx3 wrote:130k miles roughly... yeah you need rings/waterpump/& timing belt.

I disagree. If it's not burning oil other than at startup, I'd just do the valve stem seals and drive it. It doesnt cost much and you can do it without removing the head. If you needed rings you'd see excess oil going out of the head through the PCV valve. If you throw a timing belt or develope a water pump leak...well you would have eventually anyway...but you likely won't.

If you were taking the engine out of the car I would agree, do the timing belt and water pump, but you're not and there's no indication that you need to. Valve stem seals can easily be done with the engine in place and the head on for about $30 worth of tools and the cost of the seals.

I agree! just change the seals.. it won't hurt anything, and the engine WON'T see extra compression or extra pressure or anything like that.

Unless the valve guides are completely trashed, and even then, it won't hurt anything, except the fancy new seals you just installed.

7

I agree with wytbishop that you should just do the valve guide seals. I have also done this on many vehicles in the past and had no problem. As wytbishop said there is no high pressure involved, it is usually just that the seals have worn out allowing the oil to pass by. With the cost factor being negligable you can't really lose. If it turns out that you develope a problem down the road then you could make a decision as to either replace or rebuild the engine. I am presently driving a vehicle that I had to replace the stem seals, they had dried out from the vehicle sitting for a couple of years. I have driven around 45,000 miles since I replaced them and everything is just great. Bottom line is to do what you feel is needed.

OldMan

I'm gonna post a little write up on how to change the valve stem seals without removing the head. In case other people are cuious abou thow its done.

can u do the same on a K8 ?