Dohc Valve Oil Seals

[Guest Guy]

I've got a DOHC 2.0i that smokes lots, even when it's warmed up it smokes when I rev it.

 

I'm presuming that if I change the valve oil seals then the problem will go away.

 

How hard it this to do on a DOHC?

 

Is it likely to be anything else?

[Guest Stuart Ainslie]

Guy,

 

I always thought that the sign of duff oil seals was smoking only on start-up - oil lying in the valvegear runs down the stems into the bores and gets burnt on start up.

I would have thought that smoking when revving would be a sign of duff bores and rings...

 

 

Stuart.

[Les Welsher]

Guy,

I had the same thing when revin the engine hard to take a noise test before SVA.(lots of smoke)

Engine seemed to have been running fine till then, I put it down to the valve seals hardening with the engine not being used for a long time while I built the car as I had changed the piston rings.

Took the head off and changed the seals(seals were hard as hell), bingo, no smoke.

Check this link for a few tips and pics.

http://www.geocities.com/leswelsher/Dairyseven.html

A compression test wouldn't be a bad idea though.

 

Les

 

Just noticed you have a pinto in your kit car, is the DOHC engine in a sierra then.

[Guest Guy]

Thanks for that Les, it's a great help

 

I've been given a free DOHC Sierra and I want to use it as a daily runabout befor I take it to bits to make somthing else. But it smokes like Bob Hope! also it's got a leaky rear brake caliper.

 

Do I realy have to take the head off, cant I just fill it with rope like a Pinto?

 

What about the timing chain, is it easy to get off the cam shafts?

[Les Welsher]

Guy,

don't know about the rope trick, maybe worth a try if you can make up a good levering tool to compress the springs(two per valve), the most you got to lose is you'll have to take the head off anyway.

I've taken the head off three times now and it doesn't take me long.

The timing chain just slips off the sprockets once they are unbolted from the front of the cam shafts.

If you turn the engine over by hand several times until the marks on the sprockets and the copper links on the chain line up (TDC) before you undo anything it's simple to bolt the sprockets back on with the chain keeping the timing correct.

Also depends on what you're going to do with the engine and how much you want to spend

Valve seals under £10, chain tensioner just under £30, timing chain £23

 

Les

[Guest Guy]

Thanks for the infomation Les, I made a tool to compress the valvs and filled the bores with rope, it worked a treat. Some of the oil seals were not pushed into the base at all and they were all loose on the valves, they almost fell out.

 

They're all done now and I've just got to put the cam shafts back together.

 

I looked at your method of re-setting the chain tenchener, do I have to do this or can I just put it back as it is?

[Guest Guy]

You can see the collets better on this one.

[Les Welsher]

Nice one Guy,

What is that thing you used to push down on the top of the springs?

 

The chain tensioner has to be reset as there are small grooves in the body that the spring clip goes into allowing the piston to come out but prevent it going back in, this maintains some tension on the chain when starting the engine until oil pressure takes over.

As soon as you removed the chain, the tensioner piston would have moved out to the fully extended position, the spring clip will prevent the piston from being pushed back in giving you excessive tension if you did manage to force the chain back on.

Because of this Mr Ford expect you to use a new tensioner every time you remove the chain. That is why I worked out how to reset it, as I didn't want to replace my new tensioner with another new one. ( I would have bought three by now)

 

Les

[Guest Guy]

I've looked at your instructions for the chain tensioner and worked out how to do it, I'll do it tonight.

 

With referance to the picture, the long metal bar is a piece of gas pipe, the M8 bolt pushes onto a swinging arm washer from a motorbike with the side cut off, then there is a bit of 25mm steal bar with one side cut away and bent apart, this pushes on a stearing top yolk washer from a motorbike wich spreds the load onto the top of the valve spring assembly.

 

I pulled the collets out with a magnet on a stick.

 

Getting them back in is easy, just a bit of oil to give some serface tension and life is good

[Les Welsher]

Guy,

just heed my warning at the end of the instructions, safety first you know.

 

Les

[Guest Guy]

Thanks for all the advice Les, I've got the engine running again and all seems okay

[Les Welsher]

Guy,

I guess it's given up smoking then

 

Les