Oil Pressure Sensor Problems/Metallic Rattle Sound after Rebuild

Hi, Thanks to the help I have received previously and it may just be a case of redirecting me to the correct topic/thread.

My 1985 GTi Cabriolet needed new injectors, but as this resulted in some sheared head bolts I went for an engine rebuild with new piston rings, mild piper cam and 4-2-1 exhaust as the manifold was cracked, however:

1) The oil pressure sensor starts to buzz until the coolant temperature is up to temperature.  The light also blinks when the ignition key goes on and doesn't remain on until the engine is cranked.  I have seen posts about the earthing to the side of the MAF.

2) There is a metallic rattle which sounds like a heat shield but isn't when the car hits about 2500-3500 revs and only when under load.  It sounds like it is low and to the back of the engine but this is could be misleading.  Again lots of posts online, but yet to find a cause or solution.

3) The vernier pulley didn't want to line up correctly or wouldn't start when it did, so the old cambelt pulley is on at the original position.  Car runs well on idle or low revs, except for pulling away.

Not sure if these are all related?  They seem like reoccurring issues and I only seem to have a solution to the oil pressure sensor, but will replace the low and high sensors once I can source part numbers as an electrical test on the high pressure sensor is not getting any voltage, before I have the dash out.

Thanks, as always, for any help or suggestions.

Well, don't know about the cam pulley, as you have a different Cam in relation to the OEM pulley there are betters than I for that.

Oil pressure probably is a Broken sender wire

Rattles well the 4-2-to dual down pipe may have changed the alignment of your pipes, and now they are hitting the heat shield as your hangers may have broken or weakened.  So a inspection is needed and any close proximities have to be adjusted.  I know that when I changed I had to modify, as in beat, pound and adjust things a wee bit to keep the rattles at bay, and a vibrating front heat shield can have the noise travel down the pipes and sound like somewheres else.

Thanks for the quick response.  Had the car up on the ramp this morning, the heat shield (fabricated to stop melting the steering column rubber) is fine and the pipes had been modified slightly to fit and clear. It sounds bottom end and only under load.  It gets worse if you are in a higher gear but happens at mid range revs and then goes.  V odd.

Anything that sounds like it is coming from the bottom end is worth investigating. Might be worth taking the sump off and looking for any signs of metal on metal wear. I had a rebuilt bottom end destroy itself.

Did the oil pump get changed? worth taking sump off and checking. if blockage will cause the metallic sound and also the buzzer to sound as pressure and flow reduced

Thank you. Will pass on to garage.

I would check the timing - could the rattle you are hearing be 'pinking' caused by the timing out?

Thanks. Would the pinking sound like a metallic rattle? It happens mid-rev range and then goes.

What type of fuel are you using?

By the book standard timing set up is for super unleaded petrol, the timing needs to be retarded if you use normal unleaded petrol.
I found my car runs best on super unleaded petrol.

Good point.  Normally super unleaded, but the garage drained the tank and put in some new fuel, the one near them doesn't offer Super. Thanks

Yep, pinking can sound a bit like a metallic rattle, definitely worth ruling out

Then that could be why you are hearing a "pinking" noise under acceleration, depending on how much fuel you have in the car but if low try and fill the tank with super unleaded and see if that helps?
If it's full then drive it carefully and avoid hard acceleration, use up the petrol and stick in some super unleaded. .   

 You might be lucky and this could be the simple fix?

Shall give it a go, keep my fingers crossed and let you know.  Would be great to get one simple fix with a Golf!