Hi All!
Some others provided some really insightful feedback regarding this job, so i thought i'd put in my tuppence worth to hopefully make people's lives easier. The job is straight forward, just fiddly in places. I used the Besian DIY which is very easy to follow.
Outcome: Totally worth it. I was skeptical about everyones claims as the car felt strong before. I wasn't searching for any gains, especially with a total outlay of only £45! From the moment the idle settled at warm up however, i could immediately notice a difference. I always remember my Dad and his friends saying that an I6 motor isn't tuned properly until you can stand up a £1 coin on the head. Before, the Z would shake off a £1 coin lying down... Now you can stand up a penny!
Torque is noticeably stronger and smoother from 1500-2500 - only now i realise there must've been a massive flat spot before. The biggest thing I've noticed is that for the first time in 8 years I can make 2 consecutive gear changes smoothly!
My VANOS seals were definitely worn out. The pistons had virtually zero resistance and wouldn't even hold room-temperature oil at ambient pressure.
Some little tips that i would strongly recommend with hindsight:
1. Make sure you have a magnetic pick-up tool. The VANOS bolts are fiddly to remove/replace with big hands, so you're likely to drop some into the under tray. if you don't have one, remove the under tray - this will help with draining coolant.
2. I managed to crack my thermostat housing (like a tit) - it was already leaking however, so no big deal! Like many have said, the head studs can be too long to get the VANOS out without some prying. I was using a wooden 1"x2" length of timber on the exhaust side of the engine (to push the engine back 1-2mm) and another to pry the VANOS out (being careful to avoid the stat housing of course). Unfortunately the VANOS slipped slightly and slipped to 45-degrees as it freed from a stud, literally tapping the thermostat housing and cracking it.
Next time i would loosen the bolts of the 'stat housing ~5mm, to allow it wobble. This would both prevent the above from happening, and it will make it easier for the VANOS to clear the Coolant Temp Sensor connector. One of my 10mm bolts sheared, so i needed to use a spare - this was corroded due to the housing leaking slightly.
3. You only need 90 degree pliers, you don't need straight or 45 degree.
4. I had a VANOS nut thread shear when trying to torque them (only 8NM!) onto the head studs. You may want to make sure you get a box of standard spares!
5. I had an air-lock after re-filling the coolant. It turns out that the M52/54 engine *can* be a pain to bleed. Start off parking with the engine upward (tilted driveway, jack etc). Leaving the engine off with the coolant filler cap off; set cabin fans to hot, half fan speed and leave for a few minutes. Then turn the engine on and let it come up to operating temperature - making sure the fans blow warm air and screw on the coolant cap. I would then take a drive for 5 minutes, get the RPM up to over 3k, and take some water with you - Check the coolant level 15 minutes after stopping the engine (beware for Steam!) and top up if necessary.
6. Remove your battery while doing the job. Not only for some slight piece of mind, but also to reset your ECU (which mine needed). I did this job along with a Valve Cover Gasket, DISA gasket and Throttle body boot. The car must've been so utterly confused afterward that it wouldn't start or idle without throttle input. After an ECU reset, the car started instantly and ran as smooth as butter.
All the best
Some others provided some really insightful feedback regarding this job, so i thought i'd put in my tuppence worth to hopefully make people's lives easier. The job is straight forward, just fiddly in places. I used the Besian DIY which is very easy to follow.
Outcome: Totally worth it. I was skeptical about everyones claims as the car felt strong before. I wasn't searching for any gains, especially with a total outlay of only £45! From the moment the idle settled at warm up however, i could immediately notice a difference. I always remember my Dad and his friends saying that an I6 motor isn't tuned properly until you can stand up a £1 coin on the head. Before, the Z would shake off a £1 coin lying down... Now you can stand up a penny!
Torque is noticeably stronger and smoother from 1500-2500 - only now i realise there must've been a massive flat spot before. The biggest thing I've noticed is that for the first time in 8 years I can make 2 consecutive gear changes smoothly!
My VANOS seals were definitely worn out. The pistons had virtually zero resistance and wouldn't even hold room-temperature oil at ambient pressure.
Some little tips that i would strongly recommend with hindsight:
1. Make sure you have a magnetic pick-up tool. The VANOS bolts are fiddly to remove/replace with big hands, so you're likely to drop some into the under tray. if you don't have one, remove the under tray - this will help with draining coolant.
2. I managed to crack my thermostat housing (like a tit) - it was already leaking however, so no big deal! Like many have said, the head studs can be too long to get the VANOS out without some prying. I was using a wooden 1"x2" length of timber on the exhaust side of the engine (to push the engine back 1-2mm) and another to pry the VANOS out (being careful to avoid the stat housing of course). Unfortunately the VANOS slipped slightly and slipped to 45-degrees as it freed from a stud, literally tapping the thermostat housing and cracking it.
Next time i would loosen the bolts of the 'stat housing ~5mm, to allow it wobble. This would both prevent the above from happening, and it will make it easier for the VANOS to clear the Coolant Temp Sensor connector. One of my 10mm bolts sheared, so i needed to use a spare - this was corroded due to the housing leaking slightly.
3. You only need 90 degree pliers, you don't need straight or 45 degree.
4. I had a VANOS nut thread shear when trying to torque them (only 8NM!) onto the head studs. You may want to make sure you get a box of standard spares!
5. I had an air-lock after re-filling the coolant. It turns out that the M52/54 engine *can* be a pain to bleed. Start off parking with the engine upward (tilted driveway, jack etc). Leaving the engine off with the coolant filler cap off; set cabin fans to hot, half fan speed and leave for a few minutes. Then turn the engine on and let it come up to operating temperature - making sure the fans blow warm air and screw on the coolant cap. I would then take a drive for 5 minutes, get the RPM up to over 3k, and take some water with you - Check the coolant level 15 minutes after stopping the engine (beware for Steam!) and top up if necessary.
6. Remove your battery while doing the job. Not only for some slight piece of mind, but also to reset your ECU (which mine needed). I did this job along with a Valve Cover Gasket, DISA gasket and Throttle body boot. The car must've been so utterly confused afterward that it wouldn't start or idle without throttle input. After an ECU reset, the car started instantly and ran as smooth as butter.
All the best