How are valve stem seals correctly installed?!?

[HondaDustR]

So my car has been burning up a quart of oil every 250 miles for the past few months and I decide it's time to try replacing valve stem seals as the first cheap option. Mistake #1 was I decided to do it as part of one big project that also involved replacing the water pump and balance shaft seals, of which I had only a day and a half before I needed the car to go to work.
To make a long story short, I managed to get through all the tough parts, including getting all the cam tower bolts off without breaking/stipping any of them, getting the valve springs off with the head still on (for cyl 1, anyway), and pulling off the old seals (which were pretty dried up and hard). Thinking it would be pretty straightforward, I find a appropriately sized deep socket to drive the new seal onto the valve guide since they fit pretty tightly, decided to tap it on with a hammer, expecting to be able to tell when it was fully installed, and ended up pushing it way too far onto the guide. ...these things definitely don't come back off in usable condition, and I only bought 8 of them! (mistake #2) I haven't been so devastated/pissed off in all my life!
So then it just turned into an experiment seeing if I could figure out a positive way to tell how far they should be installed, but that ended up mostly "lets just destroy the rest of them, throw it all back together and pretend this never happened!"

So it's been running with no valve stem seals on cyl 1 for the past 2 weeks, and I've swallowed the failure enough to order new parts and will try it again next week (burned 5 qts of oil going to Kentucky and back...that's $6 x 5...plus gas!)

So, the big question is, how are these stupid things properly installed? How much leway do they have in terms of position on the valve guide between getting pushed on as far as possible without deforming the seals and not far enough so they risk coming off/hitting the valve spring retainer? Is there any specification? The factory manual is pretty vague. I thought this part was going to be easy (mistake #3)...

The other thing I noticed was the exahst valve felt kind of loose in the guide. I wouldn't be surprised if the valve guide was shot, as the intake felt nice and tight. Do the exhaust valves have more play due to more thermal expansion, or is it done.
Another question is how air tight are normal cylinders supposed to be? I resorted to rigging up a compression tester fitting to an air compressor to hold the valves (I couldn't get the rope trick to work to save my life), and the thing would only build up about 40 psi. I was using a portable air compressor designed stuff like filling tires, but it's rated at 1 cfm at 30 psi and can normally build up 80 psi no problem. I could definitely hear air leaking quite a bit inside the engine, but couldn't tell exactly where it was going. I'm thinking the exaust valve seats are in bad shape, since they felt pretty rough when pulling the valve against the seat and rotating it, and the guide also felt worn, possibly causing the seat to wear out funny. It could be piston rings/cyl wall since it seemed like it might have been coming through the crankcase breather hose.

Thanks in advance!

[ScoobySteve]

I'd wait for many944s to reply. He rebuilds heads all the time.

[many944s]

The excessive play in the exhaust valve means that the guide will need to be replaced. The exhaust guides on these engines usually wear out long before the intake guides do!

As for installing the seals:
if you look inside the stem seal (from the top or smaller opening) you will see there is a small (1/16" or so) shoulder of seal material. The best way to install the seal is to lightly lube it (I use 2 stroke oil). and slowly tap it into place. This is alot easier to do on a rebuild fixture so you know it is going on straight! Tap it a few times, then check the clearance from the shoulder of the seal to the top of the guide, repeating until the shoulder just comes to rest on the guide but doesn't deform.

Also, if the guides are to be reused, make sure ALL of the old seal material is removed from the exposed guide! This is easily done with scotchbrite. If there is old seal material there, it will grab the new seal and not allow it to seat properly.

Hope it helps!
-Nick

[HondaDustR]

Ok, thanks. I definitely know about the little 1/16" step inside the seal, but I'm doing this with the head still on the car, which means the valves are still in place, which means the only thing I can see is the outside of the valve guide and seal. Maybe there's a way to temporarily remove the spring and gently pry the seal lip away from the valve stem to see the shoulder inside the seal.
Between the scotchbrite and some assembly lube, I'm thinking I might actually be able to force them on by hand using a deep socket, where I would be much less likely to tap them too far. I just got my new parts, including 12 seals and a valve guide to experiment with fitment.

In your experience with rebuilding heads, do worn valve guides usually mean worn valve seats since the valve doesn't necessarily stay on a fixed axis anymore? I'm curious about where my compression is likely going.


Armed with fresh information, I enter the valve job of doom once again...

[strath44]

(will continue this good thread rather than start another one)

I've just picked up V Reinz Valve stem oil seals.

My old ones came off very easily will a little heat from torch.

The valve guides are in good condition and show absolutely minimal valve movement (side to side).

On close inspection my guides have the little ribs which I believe means they don't need a glue etc to hold them on.

I have only bought 8 selas and wondered what the best way to put them on is.

When you mention using a socket what sort of size are you using? Where is the pressure put - on the rounded sides, the little coil or the top - don't want to damage them!?

I have a corkscrew type valve spring compressor would this be a good way to put them on with a suitable size socket??

[HondaDustR]

The "absolutely minimal valve movement" and the ribbed valve guides tells me they may have been replaced recently, which is good. The genuine Porsche guides are smooth all the way up and down the outside, save for a very fine grooved pattern encircling the outside, left from turning them on a lathe, or however they machine them. The aftermarket Canyon brand you can buy anywhere else has 3 or 4 larger ribs on the end to help grip the seal.

I used a deep socket (13mm or close) to push them on. Make sure all of the old seal material is scrubbed off the guide or it can tear away the rubber on the new onewhen installed. The vitton rubber will come apart fairly easily. The socket edge should make contact only on the outer metal ring. Smear some engine assembly lube or moly-graphite grease on the end of the guide and inside the seal to help it slide on and make sure you push them on as squarely as possible. Just push firmly and steadily, rocking the socket around the seal in small circles helps to work it on there if it fits really tightly. Just go until the guide makes contact with the little moulded step inside the seal where it begins to converge down to the smaller valve stem openning, but not squished against it so hard it starts buldging the rubber out the top of the metal ring, or the seal lip won't sit correctly on the valve stem.

You know how this "good" thead ended, right?

[strath44]

I think so did it involve paper towels??

Thanks for all that will have a go over the weekend!

[HondaDustR]

Yeah, since I pulled it off with the head still on the car, I plugged the oil return holes with paper towels so I wouldn't lose anything down there. I got interupted midway, and they never came out. The rest wasn't good.

GL with it.

[bebbetufs]

I'll just pick up this thread since I have the same questions.

HondaDustR: How did you end up doing it in the end? Did you just press them on like you described? By the way, how many miles on your car?

Could one not cut a piece of plastic tubing in the correct height and slot it so that it may be snapped around the valve guide? That way one would only need to tap the seal as far as the plastic tube.

[carlege]

Originally Posted by HondaDustR

Yeah, since I pulled it off with the head still on the car, I plugged the oil return holes with paper towels so I wouldn't lose anything down there. I got interupted midway, and they never came out. The rest wasn't good.

GL with it.

Paper towls huh? I remember you using paper towels before howd that work out? I would have opted for tape

[emoore924]

Towels, tape, whatever. It doesn't matter if you forget to remove it before startup...

[HondaDustR]

Yes, I just pressed them on with a 13mm deep socket. It's pretty easy to see if they're on far enough if you are doing it on a head that's off the car with the valves removed. Doing it with the valves still installed, I got a straightened paper clip, slipped a pin between an already installed seal and valve stem to pry it away just enough to slide the paperclip down until it touched the valve guide, basicly taking a depth measurement. Then I would keep checking the seal as I was installing until the depth was the same. Tedious, but they start fitting very tightly as they get close to the proper depth, some fit tighter than others, and you do not feel when they go on too far if you use a hammer. It is possible to pull them back off and start over if you are really careful with an open ended wrench or other prying mechanism, but they do not seal against the valve stem well if they are installed past the little molded step inside. Some of them I had to push very hard to get them on, rotating the pressure around the seal helped, and you also have to be careful to get them on as squarely as possible. I'm sure there's some sort of special tool to do this with, which I've heard you definitely need if you use the white teflon seals.

The car has 157K, but the motor (from another car) only has ~ 3200 since the rebuild. No smoking or oil consumption, save for a leaking RMS.

[bebbetufs]

Ok. sounds quite interesting. I'm not changing the head gasket so the head is still on. Is the compressed air strong enough to hold the valves in place when you do this? With piston at tdc, can the valves fall into the sylinder if the pressure is lost ?

[HondaDustR]

Yes, compressed air is definitely strong enough, and the valves cannot fall into the cylinder or otherwise fall far enough in that you can't grab the stem to pull them up when that cylinder is at TDC. I didn't have a proper air compressor at the time, but rigged up a big tire compressor that had enough flow to maintain about 40-50 lb. I didn't have any problem with that, but keep in mind that pressure can push the piston down and cause the engine to rotate, especially if it's not exactly at TDC and even more easily at higher pressures. A flywheel lock, or 5th gear with the parking brake set and the wheels blocked should be used.
I also had to rap on the top spring retainers with a hammer to break them free from the valve keepers, since the tapered parts seemed to bond together from being a tapered fit pushed together under constant high pressure. Just small sharp taps around the edge of it, being very careful not to hit the end of the valve stem itself. Then just compress the spring and it will come apart. Once the spring is compressed, if it is still stuck, more taps with the spring pressure taken off will probably free them. Higher air pressure may be needed to keep the valve from popping open if they're really stuck.

Be sure to plug the oil drains with rags, and make sure they're big enough so that there's no way you'll be able to accidentally assemble everything without removing them.

Buy at least a couple extra seals just in case. They usually get mangled if you need to remove one if it got installed wrong, most likely from being pressed on too far. I went so far as to buy a replacement valve guide so I could install a seal onto it being able to easily see when it was at the correct installed depth and I used that for my depth comparisons with the paper clip wire. There should be no excessive bulging of the rubber seal where it meets the metal ring once installed, being caused by the guide going past the little molded step and beginning to spread the seal out away from the valve stem. It's also easier to get the new seals over the valve stems without cutting them on the keeper grooves if you remove the little round spring first. There's of course another special tool used to cover the valve stems so they can't damage the seals, but I can't imagine it's much more than a thin rubber cap or something that can't just be made with a piece of duct tape. I was lazy and just slid them on without anything more than lots of grease. Don't forget to re-install the round spring ring before re-installing the valve springs, and use plenty of assembly lube on the seals so they don't burn on startup.

[bebbetufs]

Thanks a bunch for a very informative answer. Much appreciated

[djnolan]

Number one cylinder spark plug is fouling out, and am burning a quart every 500 or so.
What tools do I need to replace guide seals with the head on?

I better do a leakdown first to make sure.

Here is a good video of the procedure.
Fitting new valve guide seals without removing the cylinder head Suzuki Vitara - YouTube

[HondaDustR]

AYou will need the long shank 6mm hex bit to get the cam housing off, a spark plug air hose adapter to pressurize the cyl at TDC to hold the valves shut, compressed air to pressurize the cylinder, a suitable valve spring compressor, more than just 8 new valve stem seals in case you mangle one, and LOTS of patience.

This was the exact job that led to the destruction of my original engine. You must plug the 4 oil return drains in the head so that you do not drop any valve keepers down into the engine, because after they finally decide to come out, that's where they will make every effort to go, and those drains do not drop directly into the crankcase! Use shop towel plugs big enough that there's no way you can leave them in there if you get side tracked.

You will want some sort of way to measure the installed depth of the seals, as they slip onto the end of the guide and they fit so tight that they require driving them on with a hammer and suitable tool (13mm deep socket worked for me). They also absolutely must be driven straight or they will probably leak! It is easy to tap them too far, which will compromise their sealing ability by spreading the sealing lip out. There is a step moulded in the inside of the seal which should be flush with the valve guide. They are virtually impossible to remove once installed, so you absolutely should have extras (made that mistake, too). Buy the dark red colored vitton seals. They last much longer than the black ones that come in the victor reinz kit. The valve springs are extremely heavy, so it is a nightmare getting them released without a good valve spring compressor. The cheap overhead claw looking one with the crank knob will work, but it is a miserable thing to use and will not compress far enough unless you get the tangs jammed into the valve coils as close to the head as possible. I don't have the picture on me now, but i have seen a 928 guy use one of those overhead lever type spring compressors meant for rocker arm valvetrain and just cut a short piece of ~1/2" pipe with a bolt hole drilled through it so it can be attached to the head using the cam housing bolts to act as a substitute rocker arm shaft to lever against. It looked like a much nicer setup. I was ready to put that screw type compressor through a wall by the time I was done.

[djnolan]

Will this spring compressor work? I don't mind paying for it if it saves my engine...

Porsche 928, 944 and 968 Valve Spring Compressor

Is there a procedure for removing the cam housing? I seem to recall reading something about the lifters dropping out and needing to keep them in order.

Finally how many hours do you estimate the job will take?

[HondaDustR]

That spring compressor should work fine. It looks like a purpose built version of what I was trying to explain. Clarks garage should have some info on the specifics of removing the cam housing. You will need a new cam housing gasket, and also will need to re tension the cam belt. The lifters should be kept in order if possible, but it's not the end of the world if they get mixed up. Just tilt the cam housing carefully towards the exhaust side and turn upside down to keep them in. The housing bolts will be very stuck, so be sure to rap on them with a punch and hammer to help break up the corrosion. The aluminum plugs that allow access to the inner bolts that you need the long shank hex bit for can also be pretty stuck. I actually broke off a 3/8" drive hex bit trying to get them off the first time. Best way is to use an open end wrench on the shank of the hex bit and offset 180 degrees from the hex driver handle to make a makeshift T handle tool that will allow you to pop them loose without putting too much side load on the brittle hex bit. Put some duct tape or similar around your long shank hex bit where it would contact the threads on the access holes so it doesn't damage the threads when the bolt pops loose, and spend the money for a good quality hex bit (SK, SnapOn, etc.)...it is incredible how much force it takes through that shank to break them loose, and the last thing you need is for the tool to break or to strip out the bolt head due to poor tool steel or bad sizing. The job can easily take all day for an experienced wrench, and could take longer depending on if you break any cam housing bolts. The secret is to snug each bolt.back down as you break them free in order to prevent the pressure of the valve springs from pushing the housing up and torquing sideways on the remaning bolts, making them much harder to break loose.

[Slam]

HondaDustR: best description of this job, ever. This thread is a must-read for those who've never tackled the cam housing.