Valve guides and head

[Stringer]

Hi
Please give me your opinion on whether the valve guides can be changed on a 1987 M103 while the head stays on. I have read some articles which seem to suggest that with a special valve spring compressor, you can remove the collets, then pull off the valve guides and pop on new ones - i guess while the valve it just hanging there (or, i suppose you must hold it to stop it falling down into the chamber. Is this process only if you have a pressurized chamber with an air pump?

All your advice greatly appreciated. For those who regularly help me with my project, i have just discovered that at least 3 of my pots have oil leaking into them (when the engine reaches about 81 degrees), which fouls up the plug.
(I also took the car for a scan and it found that 2 injectors were partially blocked so i changed them)
best
m in Beirut

 

[Tinkerer]

Not too sure on the anatomy of a M103 but I have heard of similar on other engines whereby you have to put the piston to TDC on the cylinder that you are working on which prevents the valves from dropping into the cylinder. Just how you remove the valve guides in this condition eludes me as I thought that most were a shrink/press fit and in these circumstances the chance of bending a valve seems very good ........... very good luck!

 

[streethawk]

I think your talking about changing the stem seals not the valve guides as the guides are a interference fit and impossible to do whilst head is on! Stem seals just pull off with some good pliers and new ones just tap into place with say a socket that fits around the metal collar! Never heard of doing it with head on and never seen a spring compressor to do it like that. If such a thing is available then you would need a very deep socket or make a tool to get down the length of the valve stem. Post back your results if you manage it as Iam interested ta.

 

[Stringer]

hi streethawk
Yes, you're right. i'm talking about the valve guides, a job i've done a couple of times over the years, so i should know better. Take a look at this new super-duper valve spring compressor which at first glance looks like a corkscrew. I'm thinking that if you brought the piston up to tdc, then you could use this type of compresssor to take off the collets and remove the guides. When you removed the collets and pull the spring away, i guess the valve might fall a bit but it would come into contact with the piston and just sit there, right? I mean, why does one HAVE to remove the bloody head with this new gadget? It looks great. I have attached it here for you to take a gander
IN FACT, there wouldn't be any worry about the valve falling 'down' as with the guide still in place, you could hold it while you pull the guidie up the stem, right?
m in beirut

 

[Bellow]

I've seen this done on an original (60s) Cooper S with a suitably bent screwdriver through the plug hole to prop the valve up, and an open ended spanner used as spring compressor. A lot easier on a push-rod motor than OHC.
I've also heard of inflatable bladders used to prop up valves, though never seen one used.

 

[brigadier]

how can you pull the guide out from top? they usually fit in very tight. you have to drive them out. some times the head needs to get heated up.
same thing with new guides. you're supposed to keep them in the freezer and heat up the head before installing.

 

[streethawk]

Iam with you brigadier on that unless it was the stem seals then maybe that's possible but not the guides! Iam an engineer and had to replace some for a mate in a vw flat 4 and they took some getting out on my machine let alone trying to do it on the car.

 

[jaymanek]

Yes you can do the seals that way but not guides......

Its quite labour intensive to do the seals with the head attached...
One at a time, remove the springs (special tool as above), collets etc, use pressurised air to keep the valves up with a spark plug hole attachment... one by one... and if like me you are doing it on a V8 its a good couple of days work.

Its quite often simpler to remove the head, however I didnt want to disturb the original head gasket on my V8 as they are not known to fail.

You deffo cannot do guides that way... The company I use will nitrogen freeze the guides and warm the head to get them in without damage.

 

[Bellow]

hi streethawk
Yes, you're right. i'm talking about the valve guides,

..

 

[Stringer]

sorry, i meant the seals, but some of you got what i meant. Bellow reckons you can't do them though without pressurising the chamber, but i think you can as when you remove the spring itself, the valves will still stay in place right? (i mean they have still got the seal on holding them tight, no?)
M in Beirut

 

[Stringer]

Jaymanek, but tell me why it's essential to use the compressed air. Couldn't i just put each piston in turn up to tdc and be careful not to let the valve go, when it's free? I mean, the compressed air is a good idea, but it's not essential, right?
M in Beirut

 

[brigadier]

you can change the seals with head in place - like you say just turn the cilinder you're working on to tdc. you can unscrew plugs to check that the piston is actually at tdc, before removing springs.

 

[Dieselman]

Jaymanek, but tell me why it's essential to use the compressed air. Couldn't i just put each piston in turn up to tdc and be careful not to let the valve go, when it's free? I mean, the compressed air is a good idea, but it's not essential, right?
M in Beirut

You need to stop the valve dropping at all, otherwise you can't get the collet back on.

I have used a small screwdriver through a plug hole before, another method is to push string into the cylinder to support the valve.

 

[Noustie]

If it's just the valve seals then you can use a long piece of string pushed in through the plug hole and then turn that cylinder to TDC. Make sure you leave the end of the string out of the hole though!

 

[Noustie]

You got there before me DM!

 

[brigadier]

good point dieselman, i hadn't tought of that. i lifted the head when i did the guides.

 

[Stringer]

thanks for that noustie and dieselman (nice to have you back DM). But if I'm allowed one last annoying question, can i Colombo you ma'am with this:

Wouldn't the NEW seal hold the valve tightly in place anyway, so you wouldn't need to worry about the string or the bendy screwdriver inside the pot? I mean with the new seal on, wouldn't the valve stay in the fully extended position while you put back the collets?
thanks for your patience
m in beirut

 

[Stringer]

)i()

 

[jaymanek]

No the seal itself may not hold the valve up and how will you get the old seals off without the valve dropping down?!

Compressed air is the best method.. it keeps the valve tightly closed.

 

[Stringer]

I'm surprised of your response as i did this job twice before - once on an old volvo and then again on a pretty old Audi and although both times it was with the head off, i found that the valves stayed in place once you banged on a new seal. I i usually found that with worn seals they can easily be slid up the stem of the valve pretty easily with pliars - unless of course there is something different about the m103 valves....?