Changing Zetec Valve stem seals

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Changing Zetec Valve stem seals

Post by Davespages on Mon Feb 11, 2008 7:10 am

In general Blue smoke on a petrol engine means one thing... Burning Oil.

If the oil is not re-entering the engine via the induction system via crankcase breather pipes or a vacuum hose on the inlet manifold... then the cause can be somewhat more sinister.

The Department of transport say...
- Vehicles were most likely to be seen emitting blue smoke when accelerating from idle, for example at traffic lights, or when moving slowly in heavy urban traffic.
- Petrol vehicles between eight and twelve years old were most likely to be seen emitting blue smoke.
- Inspection of petrol engines found worn and hardened valve guide oil seals were a major cause of blue smoke emissions in petrol engines;
- Blue smoke emissions from diesel engines seemed more likely to be caused by bore wear and piston ring problems than was the case with petrol engines.

In other words Blue smoke from a petrol engine is usually caused by worn valve stem seals or damaged guides.

If Valve Guides are the issue (and you can only find this out by stripping the head) then new guides can be pressed into the head but for the labour charges... its more cost effective to clean up a replacement head from a breakers and fit new stem seals into that.

Before anything else, consider the fact that the head gasket could have gone... water / oil getting into places it shouldn't.
(Its rare on the zetec engine but not unheard of)

DO A COMPRESSION TEST, 6 Rotations of the engine should give you a reading, this can varym mine averaged around 190-200psi
The actual pressure does not matter so much, more the differences between the cylinders... 20psi difference is tolerable, after that... you have a problem with valves not seating correctly, piston rings or a blown gasket.
To see if its piston rings do the test again but just before you do... pour a little bit of oil in the cylinder.
This will make a seal around the piston and raise the figure if the piston rings are shot.
If this compression tests shows no change in compression then there is virtually no doubt its Valve Stem Seals causing the blue smoke.
Note: If the compression readings seem particularly low.. consider re-seating the valves when you do the stem seals... yes its a "ball ache" but its best to do it now and ensure the valves seal correctly on the valve seat than end up pulling the head off again to remedy this.

Right.... Stem Seals...

This is a walk through (or maybe a step by step) guide for changing the Valve stem seals on a Zetec Engine.

For a detailed guide for Strip down, inspection and rebuild of a CVH head click here

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Right, Zetec (Be it Fiesta/Escort/Mondeo)


Before you carry out any of this, you need to make sure you have ALL the required tools, gaskets, lubricants etc before you immobilise you car.

I will assume you are fairly competent mechanic or have had experience in stripping/rebuilding an engine as you could potentially cause more damage than good if you get something wrong.

If you have a Haynes (Book of lies) then you can follow that for brief removal instructions of each item.

If you remove any pipes or wires/plugs be sure to label what they are so you can refit them.

To get the head off...

- Remove Air Intake System, Air Box/Induction Kit, Unplug Air Flow Meter and remove air intake Pipe from throttle body.
- Spark Plugs and Leads
- Remove Front Drivers Wheel and Plastic Arch Liner to gain Access to the cam belt covers (You may have to move things like PAS/Coolant Reservoirs for better access)
- Remove the Aux belt for alternator, water pump, Power Steering Pump/Aircon compressor by turning the 15mm nut on the tension er clockwise and slipping the belt off.
- Drain The Colling system of coolant
- Unbolt the wiring loom from the inlet manifold, unplug the injectors, Throttle position sensor, ISCV, cam phase sensor, coilpack and thermostat housing sensors.
- Remove Lower, Middle Cam Belt Cover, Rocker Cover and Cam Belt Pulley Cover.
- Remove Exhaust Manifold (13mm nuts) Only need to pull forward off the head studs, manifold can stay attached to the down pipe in the engine bay.
- Remove Thermostat Housing and Coil Pack Bracket from the Head
- Disconnect any vacuum hoses (except the brake servo hose... this can be left connected as its quite fragile and easily broken)

The inlet manifold is awkward to remove so I found it best to remove the head and inlet manifold in one...

Only if you are competent in belting the engine from scratch (Cam belt timing) should you continue on your own, Else recruit help from a fellow grease monkey.

Firstly you need to get the engine TDC, so with the gearbox in neutral...

18mm Socket on the crank pulley and rotate the engine clockwise until the SECOND notch on the crank pulley lines up with the timing mark on the sump.



A screwdriver or better still a 20cm 3/4" socket extension bar inserted into the spark plug hole of Cylinder 1 will also indicate that Cyl 1 is Top Dead Centre as this will be the highest it goes, further rotation of the engine via the crank will see the bar sink and then rise again as the engine approaches TDC on Cyl 1.

Provided that your camshafts are timed spot on with the crank shaft at TDC then you can slot in the 5mm thick steel bar into their dowel grooves like this...



- Handbrake on, Gearbox in gear (to hold the engine at TDC)
- Slacken the cam belt tension-er using a Tx Star bit or 17mm Spanner and Slip the Cam Belt Off.
- Completely Remove the Cam belt tension-er from the head, be careful not to loose the tension spring..
- Using a Tx Star socket slacken the cam bearing caps in the order below...


But physically remove them from the head IN ORDER as not to mix them up, they must be refitted to the same position in the head.
- Remove the cam shafts.
- Using a Torx key, slacken the 10 head bolts in Descending Numerical Order (10, 9, Cool


This image is shown with the EXHAUST side at the FRONT (In the Haynes book of lies it shows the image the other way around, inlet at the front and that can be confusing)

Once all 10 stretch bolts are removed the head should lift freely from the block along with inlet manifold.
Rest the head on some cardboard (or a rag) on the slam panel and proceed with a 13mm, 10mm socket/spanner to remove the inlet manifold from the head.
Leave the inlet manifold in the engine bay.



- Remove old Head Gasket left overs from the head face using WD40 and a Stanley knife blade.
(Scrape the head face clean with the sharp edge of the blade, the WD40 lubricates the blade to help prevent scoring/cutting into the aluminium head)
- Clean the block face up in the same way (WD40 and Stanley knife blade)

Now the bit this guide (no pun intended there Laughing ) is about...

Replacing the valve guide/stem seals.

The zetec head requires a special valve spring compressor that is capable of reaching deep into the wells (hydraulic tappet bores)
This is my valve spring compressor


Get a tub and fill with fresh engine oil... a pair of pliers can be used to carefully remove the hydraulic tappets, keep these in oil as it will prevent them from emptying themselves of oil and tapping on re-fitting.


Important - Store these in order, they wear individually to their bore hole and must be re-fitted in their original location.



To remove the valve assembly we need to release the collets from the valve stem, I strongly suggest doing this ONE AT A TIME, the collets can easily go missing and 2 collets MUST be fitted to each valve stem for it to be held in correctly.

- Take the compressor and lift the lever, insert the "cage" down into the hydraulic tappet bore on-top of the valve spring upper seat and push the lever to the "lock" position.
- Position the round cup on the valve in question and with the T-bar, slowly apply pressure to the valve, this will gradually compress the valve spring and release the collets from the valve stem.
Note: A pair of Needle Nose pliers comes in handy to pick up and move the collets.

- Extract the collets, upper spring seat, valve spring, valve stem seal and the valve itself.
- Check the valve is seating correctly in is valve seat and clean the stem with a clean rag.
- If the valve stem seal has not come out with the valve spring then it will require a pair of pliers to squash it, turn it left to right and back until it just slips off.
( If it has come out with the Valve spring, it will need prizing off with a flat blade screwdriver)

This is the valve assembly...



The fit together like this (Ref: PICTURE A)



- Dip end of the valve stem in oil and re-insert the valve through the guide into the head, the oil will minimize stem wear on re-assembly.


- Valve Stem and Seal Fitted onto Lower Valve Spring Seat


- Place the spring over the stem and the stem seal.
- Place the spring upper seat over the spring
- Compress the spring and upper seat down over the stem seal until the top lip of the valve stem is exposed enough to re-fit the collets (Again a needle nosed pliers is useful) The collets are tapered so the widest part sits at the top and "hugs" the lip of the valve stem.



TIP: Dab a drop of oil onto the collets and valve stem, it will make them sit in position easier.


The Aim is to have the Valve Assembley fitted in the head like it is in this picture...


- Do this procedure for all 16 valves



- Now refit all 16 Hydraillic tappets in the order they were removed.

Thats the Stem Seals done and dusted...

*************************************************************
Rest the Head on the slam pannel (ontop of a rag or some carboard) and refit the Inlet Manifold and if applicable, New Inlet Manifold Gasket.

Head Gasket...

- Place the gasket on the block face... Make sure the gasket is the right way up and the right way round... check all water/oil channels are clear (not blocked by the gasket) and that all 10 head bolt holes are open. Its clear the gasket only fits one way.

- Gently place the head down on the gasket, the head will locate onto two dowls that protrude from the block.



- Look down the cylinder head bolt holes.. they should line up with the holes in the gasket.
- When your happy with the alignment of the head and the block... get your BRAND NEW stretch bolts... DO NOT USE OLD BOLTS, they stretch when tightened and wont stretch the same a second time.
- New Bolts... usually come in the gasket kit... There's a protective waxy layer (like on brake discs and clutches) that MUST BE REMOVED... soak them in petrol or wd40 and clean them off, i used WD40 and wire brushed them clean.
- Failure to remove the waxy layer may cause the bolts to work loose or loose tightness.
- Place all 10 Bolts in thier holes through the head...

Now follow the tightening sequence below.



The tightening must be done in 3 stages as to reduce risk of warping the head.

Stage one.

25Nm (18lbs.ft)

Stage Two

45Nm (33lbs.ft)

Stage 3

Preferably Using a Ratchet fitted with a protractor, Angle tighten the bolts in sequence a further 105 Degree's clockwise.
If no protractor is available, i would suggest angle tightening 90 Degree's and then a tiny bit more...
If you feel the head bolt is going to give way and shear (regardless if you havn't angle tightened it or not) STOP and leave it at that.

Now that the head is on, camshafts can go in.

Dont mix up the inlet and Exhaust cam, the Inlet cam has a little metal notch at the opposite end of the pulley.... its sits inline with the cam phase sensor (top right of the head)



You may find that the camshafts wont sit snug to allow you to get them lined up like before, dont worry.

- Pour fresh engine oil over the cam shafts where the bearing caps sit, this helps lubricate the cams for the first few seconds before oil gets up to them.
- Refit the cam bearing caps in the exact order you removed them.
- Follow the tightening sequence as follows...




Again these must be tightened in 2 stages as theres a danger of snapping a camshaft!

If you have a small torque wrench then the figures you need are...

Stage 1 10Nm (7lbs.ft)
Stage 2 19Nm ( 14lbs.ft)

Otherwise, just nip them up... be carefull tho... they can and will shear off, i've done that in the past.

- With the bearing caps tightened down, you can rotate the cam shafts via thier pullies to line up thier dowl grooves with the top head face and lock them in position.
I found they were very tight and use a small bar to between the spokes of the pully to advance or retard the cams to get them lined up.

-Once in position, insert the 5mm bar into the grooves and proceed with refitting the cam belt tensioner not forgetting its tensioner spring.
- Use an allen key inserted into the tensioner to maintain tension during tightening.

- The cam belt tension should be enough so that there is no slack at all between the cam pullies.
- The belt should be tight enough so that between the exhaust cam pulley and the crank you can only twist the belt by 45 degree's. If you can twist it by 90 Degree's then its too slack.
- Same applies to the belt tension between the tensioner and the crank.


The engine and cams are now TDC and tensioned up nicely.

- Remove the 5mm bar.
- Put the gearbox in neutral
- Using an 18mm socket, turn the engine over by the crank clockwise for several rotations of the crank.... this is to check for any nasty supprises.

If all is well and good...

- Refit the Rocker Cover
- Refit the upper cam belt cover
- Refit cam belt pully cover
- Refit pipes and wires to inlet manifold
- Refit coilpack/thermostat housing
- Refit Plugs/Leads
- Refit PAS/Coolant Resivoirs and Inner Plastic wheel arch+ Drivers Wheel
- Refit Airbox, intake pipe, throttle body and airflow meter.

Start up and hopefully it will fire first time.

So there you go...

- How to change the Valve Stem Seals
- How to Remove and refit camshafts in the zetec engine
- How to re-time the zetec engine (crank to cams)

All in one guide 🔝

Dave

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Escort Gti
2.0 16v 153bhp, 141ft.lbs
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