problem after changing headgasket (timing)

[josh_gti]

hi guys

i picked up a mk2 gti 8v a few days ago which had a blown headgasket i changed the headgasket and it now has 12.5 compression across all cylinder, i put the cam belt on with the tdc mark on the flywheel in the middle of the peep hole on the gearbox, the mark on the back of the cam pulley flush with the top of the head (not the cam cover) and the centre of the rotor arm level with the mark on the distributor housing. when i tension the cam belt the flywheel mark moves out of place ive tried moving it over a tooth but i cannot get it to line up properly when tensioned, when i start it up it runs really rough.

can anyone help? has this happened to anyone i really want to get this sorted as i need it for a daily car and to get home as im stuck round my mates till i get it sorted.

thanks in advance

[l333]

hi first thing you need to take the green bung out of the gearbox to see the arrow to line it up with second there is two marks on the flywheel ont at tdc and one 6 degrees before for ignition timing third thing sounds like you are overtightening the cambelt where about are you located?

[josh_gti]

hi mate, cheers for the reply im currently located in hatfield in hertforshire

so the green bung needs to be totally removed?

the marks on the flywheel, one is a half dimond shape which is 6 deg timing, and the other one just next to it is tdc, is this correct?

and im prity sure that im not over tightening the belt, it can be turned 90degs, even when its looser then that the crank still moves out of place.

[rubjonny]

heres a pic, you want to use the small punch mark to line up the static belt timing.


when i do the belt i fit it to the cam sprocket, then turn the cam with a spanner slowly till correct tension is achieved, recheck marks then tighten the tensioner. turn it over by hand twice and recheck marks again. if ok sorted, if not move the belt a tooth either way depending how far out it is. your smallest unit of movement is 1 tooth on the cam sprocket either way, so just get cam and crank as close as you can.  make sure dizzy is roughly lined up for now, it just needs to be close enough to fire.

once its going you have to adjust the ign timing with a gun, i recommend inductive pickup ones makes your life way easier.  use the big diamond mark for the ign timing, and give it a paint with tipex to make it easier to see.  if its a digifant 8v there is a special procedure to the timing, idle and co, so check my digifant tuning guide

[josh_gti]

so A. is tdc and B. is 6deg before tdc right?

im going to have another go at it today i will let youknow how i get on cheers

[rubjonny]

aye!

[josh_gti]

ok timings all done.

now more problems the idle keeps going up and down, am i right in thinking that its a vacume leak some were?

and the cooling fan comes on as soon as the ignition is on and i drove it for about 2hours today and the water temp didnt get passed the first white line, it didnt look like it moved at all from cold. could it be the temp sensor?

[weazgti]

Sounds like your isv needs cleaning out. As for the temp it might of had thermostat removed when it had headgasket problems to make it run cooler. Bottom rad hose will be warm straight away if its missing or knackered.

[rubjonny]

assuming the car is a digifant, sounds to me like the idle switch. check you hear it click just as the throttle comes on/off the throttle stop. make sure it shuts form to the stop as well, if not check throttle cable isnt too tight or binding up.  if that all looks ok, check the wiring to the 2 pin plug on the back of the throttle body, it loves to snap here. repair it but add in a few extra cm of length to allow engine to move.

idle switch is the one on the bottom of the throttle body, and is a bit of a pain to get to. inlet boot has to come off and you need an angle screwdriver to get to the screws that hold it on.

if all the above checks out, you can check it electrically back to ecu easily. hold the throttle just off the stop to say around 1.5k rpm, then press the WOT switch on the top of the throttle body., the revs should drop, then go back up when released

[josh_gti]

thanks for the reply i will check it out tomorrow

weazgti what is a isv? sorry, i hate being a newbe.