Subaru EJ25 Head Gasket Replacement – Part Two

Ok, with any luck you’ve got the engine out without any dramas and have it secured on an engine stand or bench, or the floor if you’ve got a better back than I have. To remove the heads the timing belt and intake manifold need to come off. We’ll tackle the timing belt first.

Timing Belt Removal

As discussed in Part One the harmonic balancer bolt should already be loose or you have an impact gun handy to loosen it. Sometimes you can get lucky with these balancer’s and a gentle pry on each side is enough to get them coming off, more often than not it will take a puller though. A large three-legged puller will do the job where the correct tool is not available.

With the balancer out of the way the timing belt covers can come off. The small passengers side cover has three 10mm bolts and the larger cover has a total of eleven 10mm bolts securing it. 

Although not essential, I like to set the engine up on tdc before removing the timing belt. Yes, it can be done later before refitting the heads but I prefer to do it now. To rotate the engine refit the balancer bolt and turn the engine in a clockwise direction until the crankshaft and camshaft marks align like so –

Crankshaft Timing Marks
Right (drivers side) camshaft timing marks
Left (passengers side) camshaft timing marks

With the marks lines up the tensioner can be removed (14mm bolt). There is a sleeve with a washer at either end in the tensioner, just be careful not to lose (or forget!) the back one as it will more than likely fall down as you remove the tensioner. If you plan of reusing the tensioner you will need a way of compressing the pushrod back into the tensioner body and a pin of some description to keep it their while refitting the belt – a bit more on this HERE.


With the tensioner removed the timing belt can come off, I find taking it off the waterpump pulley first the easiest way. There is one 10mm bolt in the right hand rear timing belt cover that has to come out.


Now we can concentrate on removing the intake manifold.

Intake Manifold Removal

First up we need to remove the injector covers. Four 12mm bolts in each one. On the drivers side there is also a 12mm bolt securing the o2 sensor connections bracket that needs to come out.




There are three electrical connections on each head that have to be disconnected, at the front on the left side (passengers side) and at the back of the head on the right (drivers) side.


And at the rear of the engine the knock sensor wiring has to be disconnected.


And at the front of the engine there are three connections to remove –


Then we have the heat riser pipe to remove, and a vacuum hose from the manifold.



And finally four 12mm bolts on each side of the manifold itself –


All going well and you’ll be able to lift the manifold up and out of the way.

On the left side the 10mm bolt securing the oil dipstick to the head can be removed and the dipstick and tube removed by rotating it around while gently pulling upwards.


From here both of the tappet cover can be removed (six 10mm bolts and watch for oil leaking out as you undo them). Then all we have is the head bolts. These head of the bolts are 14mm, however they are 12 point or double hex heads so you will need a 14mm half-inch drive double hex socket. A small extension and breaker bar will also come in handy.

The bolts will be tight so be as vigilant as possible about keeping the socket on fully and squarely or you will risk rounding off the head and we don’t want that! Some people get precious about undoing head bolts in a sequence but I figure all alloy heads that we deal with are sent away to have their face skimmed so I’m not overly concerned with this. 

As the head bolts are wound out be careful not to let the cylinder fall, and in particular don’t sit them on their face, always sit them upside down in case any valves are in the open position and at risk of getting bent like in the image below –


Once both heads are removed I suggest having a look around for the cause of your woe’s, and no I don’t mean your wife, just your car woe’s. You can read about what we found with our’s HERE. Our reconditioners are good to us and don’t have a problem removing any ancillaries they have to to do their work so at this point that is the end of this part of the tutorial. Part Three coming soon 🙂



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