New Head Poor Economy

[tomr2000]

Evening all.

I recently snapped my timing belt and needed to fit a new head, there was no damage to the pistons and only a slightly bent valve so decided to replace the head with one I found locally on eBay. The new head looked to be in great condition and apparently had only done 70k miles. I have had my golf for just over a year and have recent reached 250k miles and consistently achieved 50-60mpg. Since fitting the new head my MPG has dropped to 30-40mpg. I'm just wondering if anyone else has experienced similar issues or has any suggestions. I have been having some starting issues too with the car taking lots of turns before starting and often a couple of attempts. It always starts eventually so I'm not hugely concerned about this, mainly mentioning in case it could be connected.

Thanks!

 

[Vince Waldon]

What is the timing set to?

 

[tomr2000]

I set the timing using the official vag tool so should be spot on

 

[Vince Waldon]

Sometimes the devil is in the details: above the timing line? below the timing line? Engine coolant fully up to operating temperature?

The other big thing that can affect fuel economy... that VCDS can't check on an ALH... is crank-cam timing. That one often comes down to technique and this specific question:

Was:
- the cam sprocket loose and able to turn freely on the camshaft
- the three IP sprocket bolts loose so that the IP sprocket could turn freely
- the crankshaft at exactly TDC, using the view hole thru the transmission
- the camshaft locked with the alignment bar
- the injection pump locked with the locking pin

while you tensioned the timing belt?

Very specific, but each part is an important step to get the crank-cam timing exactly correct. The cam sprocket being loose and able to spin is the most common "miss", and crank-cam timing then gets messed up, since the belt can't equalize stress while it's being tensioned and does so after the locking jigs have been removed.

 

[garciapiano]

Did you use the proper thickness of head gasket?

 

[The Cream Dolphin]

Did you use the proper thickness of head gasket?

Exactly what I came here to say, I feel like this is an important one.

 

[tomr2000]

Afternoon,

thanks for your response. Yes all timing was set up correctly with the cam and crank shafts locked in place and loosening the cam sprocket to allow tightening without messing up the timing. I’m not sure however about the injection pump I wasn’t aware this needed to be locked. And yes the correct thickness head gasket was used.

thanks

 

[Vince Waldon]

Not having the IP shaft locked with the three sprocket bolts loose can cause it to move after the belt is tightened, same as if the cam sprocket is not loose.

Might be worth getting the engine back to TDC and seeing if the various locking jigs slide right back in.

 

[tomr2000]

Looking at diagrams for my engine (ATD) I don’t appear to have the IP on my cam belt, does this need locking elsewhere? Cam sprocket was loose so that should be fine. I did about 100 miles this evening all straight flat roads at around 60mph and achieved 38mpg so still definitely seems to be an issue