Wednesday, 14 October 2020

Does she go?

Nudge Nudge -  oh yes, she goes alright!

Between a lockdown and a pending MOT.

Lunch break shakedown test: ~34 miles of ~11ºC bracing but clear weather along lovely de-restricted (I know) A roads around Monmouth and Tintern. 60mph is plenty on a nice winding road along the Wye valley.

Even a cat-lick of a clean to make her look presentable.

The petrol isn't going to burn itself after all!

Monday, 5 October 2020

Cooling fan manual and backup stat overrides

 A little enhancement on the main engine cooling fan control.

While the ECU fan management is rock solid it is at the mercy of input sensors.

It is straightforward to add a manual switch into the fan relay coil as an override. If my temp sensor ever goes bad again the switch under the dash will let me manually turn on the engine fan.

To make things more interesting I incorporated a tri-colour LED to show on the dash when the fan is on, it sits unobtrusively bottom right of the water temp gauge.

The circuit specifically designed for minimal changes to the main loom - just a piggy back on an existing cable and if my new circuit fails - for any reason - it should not disturb or otherwise upset the existing operation of the ECU to Fan relay circuit.

Off = fan is off

Green = fan on via ECU demand

Red (ish) = fan on via Manual dash switch demand (its actually red + green but the red is more intense)

Blue = fan on via Radiator stat demand

I have a VW Polo radiator with a mounting point for a simple temp sensor which closes a switch, and for me, grounds the cable when it hits a temp limit. This is the automatic backup if the ECU sensor fails again & will light blue on the dash as a warning.


Multiple demand on at the same time light green + the appropriate colour.


The circuit itself on a Vero board mounted behind the dash with manual override switch beneath. The board is in one of the drier areas of the car but precautionary hot glue on cable ends and the board conformal coated to give it a chance in the relatively harsh environment.

All wire runs were subsequently given a second layer of insulation/soft fabric wrap too.

Emerald Pin 6

Emerald Confirmed that the ECU will not mind an external sink of pin 6 'Fan Relay control' to ground. The easiest place to tap into it on my car is near the ECU connector - a cable spliced on and suitably insulated.

These are all signal current circuits to the coil of the Fan relay - no significant current passing at any time.  Traced pin 6 to the orange wire - double checked by grounding it does turn on the fan - and spliced in my yellow feeder to the new circuit

Wrapped it all back up

That will do.

Sunday, 4 October 2020

Indicator tell-tale

The dash was off for other works and I managed to find a green, rather than the old blue, tell-tale for the 'in my face' left-right direction indicator bulb between the main clocks - thats better. 

Its only there because early on I used to forget my indicators were on, the small light in the tacho wasn't bold enough to catch my eye unless I was focused on the dash.

The red tell-tale above it is the 'lift or shift' Shift light controlled by the ECU with thinking time before the engine redlines and rev-limits.

Saturday, 1 August 2020


Feels like the time is right to get some miles in when I get the chance after the first half of year washout.

6 months road tax - sorted until Jan.

Sunday, 31 May 2020

Loose ends

A few small changes to the cooling configuration and the final step in the engine rebuild to replace a dust cover.

1. Baffle to block the air gap between the radiator fan housing and the top of the radiator.

2. Coolant cap reduced from 20PSI to 16PSI

3. Reinstall the cam belt top cover which requires the aux belt and butterfly valve (or intake assembly) to be temporarily removed so it can slide into place from the front.

Subject to UK lockdown in Wales being relaxed, hopefully in the next month or so, we should be back to square one with a fully operational Zero!

A wash is all it needs now.

Monday, 25 May 2020

She lives!

So many parts to put back, rough sequence:

- Cam cover with new gasket
- Exhaust manifold with new gasket
- Thermostat to water rail housing with newly cut gasket
- Water temp gauge sensor
- ECU water temp sensor
- Water rail
- Plugs and HT leads
- Coil connector
- Oil breather

- Cam belt middle cover
- Alternator bracket and alternator
- Water pump pulley
- Aux belt tensioner bracket
- Aux belt

- Inlet/plenum arrangement with new gaskets to the head
- Air temp sensor
- Accelerator cable
- Throttle position sensor
- IACV cable
- Fuel rail and injectors
- Injector and cam sensor loom

- Various cable tie stand offs for all fuel lines.

- Refill coolant
- Coolant cap off to monitor bubbles
- Cam sprocket cover off to monitor cam belt tension after running

....all set...

Ignition - turnover - engine fires and runs.

Oil pressure comes up immediately.

Water temp rising slowly - at around 90ºC indicated (means nothing since the gauge is not calibrated) the fan comes on - and importantly goes off. Pre head gasket change the cooling system couldn't hold the temperature down so this is a good sign.

Coolant hoses staying flexible - no longer over pressurised from combustion gases.

No white smoke from the exhaust.
On turn off just a hiss from the cooling system - no spewing into the overflow bottle.

That will do for a first test! (video)
Some project.

RESULT - She's alive!

No guarantees yet - needs a road test once the CV19 lockdown is relaxed in Wales!

All good disassembly/assembly projects should end up with a few extra parts - this one is entirely intentional. I couldn't remove it without cutting the connector off because of the alternator bracket. It isn't generally connected or used on a Zero/Emerald combination - although if it is a thermostat the emerald does support multiple temp inputs?

Not needed and no longer fitted.


Today is - camshafts back in, set timing, cam cover, alternator bracket and exhaust. 
That leaves only the intake side, fill up with coolant and see if it works again.

I didn't change the cam belt this time - its good for another 5 years & best part of 80k miles before it needs doing again.

This is not an instruction - merely notes/pictures - my guide is the Haynes manual - plus I've done this a couple of times before now. The process makes logical sense - Zetec cam sprockets are not keyed on the camshafts - they sit on a flat surface held in place only by their mushroom shaped bolts which allows infinite adjustment of position.

1. Crank vs. cam position

Timing pin sets the crankshaft position and this plate sits on the camshafts to hold them in the correct position vs the cylinders.

2. Crank vs. cam sprocket position

Timing belt is then tensioned with the left pulley adjusting until its arrow indicator is in the right place., sprockets are loose from the cam, this sets the cam sprockets relative to the  crank shaft.

3. Sprockets locked to camshafts

Then the cam sprockets are tightened locking them to the camshafts. The camshaft plate at the back is removed for tightening and replaced once done as a double check. The engine then turned by hand one cycle, two rotations and tensions/alignments double checked.

That should be it - timing set.

Sunday, 24 May 2020

Head on


Double checked my torque wrench was calibrated with a couple of known weights and created a couple of guidance dowels to help re-locate the head correctly first time.

More Cleaning

Perhaps some paranoia about clean bolt holes, merely following the Haynes manual procedure, ensuring there is no oil or muck at the blind holes to avoid any chance of cracking the block when tightening. Compressed air followed by a rag and visual inspection.

Perhaps now just putting off the big step...

Head on

Cylinders back a touch from TDC to avoid any risk of contact.
New gasket in place - double checking orientation with the picture of the old one - turns out it will only go on one way round anyway. 

Looks really nice compared to the old one!

...and slide the head back on, down the temporary dowels to locate smoothly on the block. With no picture since I had my hands full!

New head bolts then lightly oiled and fitted - 20Nm intermediate, 40Nm full torque then as pictured 90º smoothly for final tension  - all in the order as specified by Mr Haynes.

I couldn't wait to get the followers all back in place - so many of them - and all had to go back exactly where they came from. It felt like this on the face of it simplest step was just waiting for me to knock the box over or be disturbed mid job and lose track.

...and pause.

Leaning over the car is less than comfortable and I'm in no rush.
The next steps - cam shafts and timing - all need equal amounts of clear thinking to get right so now feels like a good logical point to take a break.

Thursday, 21 May 2020

Head cleanup and measure

Note - As with every part of this build - this is the first time I've done it - this is NOT a manual - its my record of what I did.

Is it flat... enough?

Haynes manual spec says: "Maximum permissible gasket surface distortion 0.1mm"
Acquired a straightedge with spec: "Tolerance below 0.03mm"
Feeler gauges: 0.04mm upwards.


While tools were on order research via a selection of youtube videos + read the Haynes manual for the engine and consult with some trusted sources.

Very light cleaning with light oil, soft softwood scraper, then isopropyl alcohol to remove any gasket residue and then inside the cylinder/valve area lubricated lightly with engine oil again and left to dry.

The gasket left behind random bits of its rubber coating which sort of peeled off in places. Some discolouration visible, but also the original machining marks visible which must be a good sign that its clean.

It feels smooth to the touch - which sounds like a daft measurement - but fingertips are incredibly sensitive to local distortion - better than sight anyway - useless for overall bend across the whole component though.

Measurement errors

Built in I have potential error of 0.03mm from the straightedge, therefore worst case the ruler could be making the head look flatter than it is by 0.03mm (if they both bend in the same direction - top scribble).

If the head bends the other way to the straightedge error then it would make things look worse  (bottom scribble) of course I can't tell which if either is happening.

Therefore to detect the worst case I need to measure 0.1-0.03 = 0.07mm flatness or better to be within spec head flatness. Take off some for errors in the measuring process and I went for a 0.05mm feeler.

Am I kidding myself - or - is that logical?

Measuring points the obvious long directions, but also diagonals and really any flat between any holes. This picture showing the sort of pattern I adopted, repeated across all cylinders/head bolt holes.

Measure method #1

Lay the straightedge on the block, attempt to slide the 0.05mm gauge underneath, checking all obvious flats and paths between openings.

Measure method #2

Lift either end of the straightedge by a known amount - 1 thickness printer paper - and using a feeler of the same thickness as the paper (or even more of the same paper) check for any differences - loose or tight spots. (Thanks for this concept Graham)

The advantage here is the thickness of feeler is no longer critical to the measurement. I can measure down to the 0.03mm straightedge tolerance with a paper thickness feeler. The gauge should make it under with that little 'grab' you would expect in all places/directions. The paper may depress during the process - but even that should get me a fail safe/better resolution.


So far - all good - consistent, no low spots no high spots identified with either method.

Left it for a day or so and repeated to make sure its not just my wishful thinking that its flat and make sure I'm comfortable with this stage before making the re-assemble vs skim decision.

Friday, 15 May 2020

Head off

The head is coming off hopefully just to replace the gasket but that depends if everything is still within spec.

Why am I doing this

The failure I believe is due to overheat caused by a failing temp sensor and lack of fan cooling when the car was stationary. i.e. I believe I have identified the root cause before this attempted fix.

Disconnecting ancillaries

Step one is dismantling, the head is coming off but to release it there are a number of steps.

Intake side: Injection rail, cam position sensor, plenum - inc accelerator cable and air temp sensor, alternator brackets x2
Exhaust side: Water rail, exhaust manifold.

First look under the cam cover and some tale-tale white on the bolt tops - coolant in the oil, corroborates the CO2 detection kit so she definitely had to come apart.

Cam shafts and followers

Water pump pulley to release the cam belt cover and cam belt, cam shafts out..

Cam followers all labelled to go back in the same place.

Parts table and boxes to try and stay organised.

Head bolts, nothing particularly noteworthy - they're not going back in.


The head lifts off - a surprisingly delicate component for a heavy block of aluminium - oil and coolant channels everywhere and the valves smaller than you might expect packed together in each cylinder. A really impressive piece of engineering - no less impressive that they were built in the tens of thousands to the same standard.


Cylinders carboned up after best part of 30k miles. Pictured with the old gasket in place and removed and liberal oil soak to clean.

First stage done.

It's all had a soak of WD40 and will sit overnight under a rag to help with cleaning and measuring up to see if everything is still flat. The operational spec on the head is max out of flat by 0.1mm!

The bigger challenge is can I put it back together and get it operational?
Worst case this will become an engine rebuild job for an engineering firm.

Update - Received knowledge (thank you) - WD40 is less than ideal for this job - it cleans, but it also strips any other lubricant or surface coating which can induce surface rust. I've since cleaned up and made sure the parts that matter have an engine oil soak/coating to ensure lubrication is maintained.