2.4 Inlet How to fit 2.4 inlet manifold to an Astra.

Right Chaps, I made a few notes as I fitted the new manifold the other day so I could write a bit of a guide for the 50 odd people who will soon be doing the same. So here goes: -

1. Jack the car up so you can get under the front and don’t forget to use an axle stand.


2. Remove the wire harness clip from the dipstick along with the plug and then remove the other four harness clips from the bottom of the intake manifold. This can be a bit of challenge in the tight space so get comfortable and try to keep your calm.


3. Disconnect the battery with a 10mm spanner. If you have an alarm you need to turn the ignition on and then disconnect the battery within 10 or 20 seconds of turning it off again to stop the alarm going off.

3. Pull the air temp sensor plug and the oil breather pipe from the intake pipe and then remove the air intake pipe by releasing the jubilee clips with a 7mm spanner.

4. Unclip the fuel rails from the plastic clamp on the side of the engine and disconnect the fuel pipes from the fuel rail with a 17mm and 19mm spanner. Put a rag over the connections as you pull the pipe from the rail as the back pressure can send fuel straight in your face with the angle of the holes. I found that the thing didn’t spit fuel at you until a few seconds after I removed the pipe and it caught me off guard.

5. Remove the 4x10mm bolts from the throttle body and remove.

6. Unplug the ECU by gently levering the metal clamps up and forward towards you. Undo the four 10mm bolts and place the ECU somewhere safe.

7. Disconnect the plug from the map sensor.

8. Remove the fuel vapour pipe connector from the manifold by squeezing the small black buttons on either side of the plug. Depending on the year of the car the fuel breather pipe valve might be attached to the front left engine lift point bracket. If it is remove the 13mm bolt, disconnect the wiring plug and move the pipe work out the way.

9. Remove the brake servo vac pipe from the lower right hand side of the manifold by again squeezing the two black buttons together. If you cant get it off then you could do this later when the manifolds on its way out and you have more room.

10. Remove the two 10mm nuts holding the black wire trunk to the head. Now you have better access its time to unplug the injectors. Again be careful, they look pretty easy to brake. Using a flat blade screwdriver, lever up the Blue tag on the plug. This allows the black lug to be pressed in, at the same time as pulling upwards to release the plug.




11. Remove the 10mm bolt from the dipstick bracket at the front of the manifold and unplug the wire harness clip. Now you can pull the dipstick from the block. It requires a wiggle but it will come, and don’t worry about the oil spilling its about an inch lower than the hole. Good idea to chuck a rag over the hole to stop any bits getting it.

12. Remove the 2x10mm nuts from the front right engine bracket to access and remove the 2x13mm bolts in the EGR pipe manifold. Then flick up the clip on the other end of the pipe where it connects to the manifold and withdraw it.
This is a good time to ensure the EGR valve is blanked off using either the Vauxhall blanking plate or your own fabricated one. I left the hole the pipe leaves behind uncovered until I get round to making another blanking plate at work.

13. Remove the bumper by removing the three plastic clips from the middle of the underside, and the two from above. Undo the fog lamp plugs and th air temp sensor from the lower grill. Then undo the T25 torque bit screws from the upper and lower arch corners. Preferably with a friend, pull the bumper forward and off. This gives access to the air con bolts.

14. Using a 3/8s drive strong arm in the square hole, pull back the auxiliary drive belt tensioner and slip the belt of the air con pump.


15. Undo the 3x E12 torque socket screws from the air con pump. This allows the pipe connected to it and in the way of removing the manifold to be moved out the way. If you haven’t got an E12 socket or you struggle to get in with it, you can use a 10mm spanner as long as there not stupidly tight.



16. Undo the radiator lower brackets using an E12 socket or again a 10mm spanner if you haven’t got one. Ease the bottom of the rad forward to allow more room for the withdrawal of the manifold.

17. Clean all around the top of the manifold where it buts up against the head. If there’s any grit or dirt here when you remove the manifold or injectors the first place it will go is in the ports which is not good and could result in scored cylinders. Clean out the holes around the injectors too if you can get to them, Perhaps use a paintbrush, vacume, air line, what ever you can get hold of really. I used a can of compressed air that’s ment for cleaning out PC’s.

18. Undo the 10mm manifold bolts and the two 10mm nuts holding it in place. I also found I had to remove the two studs with an E5 socket.

19. You can try at this point to remove the manifold but I found it wouldn’t fit past the injectors in which case you need to remove the injector rail. To do this remove the two 13mm bolts securing it in place and gently tease it out along with the injectors. Then remove the manifold.


20. Now with a clean rag, double check no grit or dirt found its way into the head ports. I put a clean rag in one hand round the back of the injector holes as I cleaned them out from the front. The pictures below show just how much dirt can build up there. Some bits did drop in on me and I got them out with a really small vacume attachment I have. You can see in the ports to the valves quite easily, so just double check.




21. Now your ready to do the Vocky alternator mod. Remove the plastic nut from the back side. Undo the two 13mm nuts and unscrew the Philips screw in the top. Now you can withdraw the end cap. Fit a suppressor as shown in the photo and reattach the main wire back to the 8mm stud at the front.


22. You can test fit the new manifold at this stage if you like. Remember you need to have removed one of the brackets on the bottom of the manifold by sawing it off so it doesn’t foul the air con pipe.


23. Refit the air con pump and the belt whilst your there. Once on I found I had to Very carefully bend the pipe forward towards the Rad to give the manifold enough clearance. This worried me a little because you could upset the pipe flange that connects it to the pump and leak air con fluid. It only needs to move 5mm or so and It went quite easily, I hope everyone else has the same successes.

24. Trial fit the manifold again if you like and check you’ve bent the pipe enough. Remove the manifold and whilst you have good access you need to file away a little of the radiator fan mounting leg so the pipe doesn’t rub against it when the rads back it properly. Even if there’s a small amount of clearance as it is, as the engine moves it may catch it so its worth doing. I found out the hard way and had to do it after I’d finished with a dremel and it wasn’t easy.



24. Now make a small bracket for the dipstick and fit it to the manifold before you put it in. Again I did it the hard way after Id just about finished installing everything and it took nearly an hour to fit the frickin screw as theres just no room for fingers. The bracket needs to have two 8mm clearance holes 35mm apart and bent like the bracket in the picture.


25. Secure the top two mounting studs to the ECU mounting plate and loosely fit the bottom right hand two studs but don’t tighten them up as they need to bend out the way to get past the front slam panel. I left the bottom left hand screw out as there’s no room for it. Now mount the plate to the manifold with some cut down 8mm bolts and nuts with thread lock so they don’t vibrate loose. (Nylock nuts wont fit in two locations)

26. Fit the original map sensor in the manifold and now could be a good time to fit your brake servo pipe to the front of the manifold if its going to be a tight fit.

27. Now fit the intake manifold for the last time and secure it with the studs, bolts and nuts you removed earlier. Don’t over tighten it as it doesn’t need to be mega tight as you probably realised when you undid them.


28. Clean the seals up on the injectors and refit the injector rail by pushing it back into place ensuring the bolt holes in the rail line up with the holes in the head as you push it in, this should keep you straight and true.

29. Refit all the injector plugs. The fuel vapour pipe and the map sensor plug.

30. Refit the front right engine mount and fuel vapour valve if removed.

31. Fit the ECU onto the mounting plate, Not forgetting to ensure the earth wire is securely fasted directly onto the ECU.

32. Clean around the bottom of the dipstick and refit that back into the hole. I found this easier to do by feeding the dipstick up from underneath the car rather than from above. It will need a fair bit of wiggling to get it in, again best done from underneath so you can see if its straight. Then secure it to the bracket using an 8mm nut and bolt as seen in the pictures of the bracket above.

33. Back underneath, secure all the wiring harness’s to the lugs on the intake manifold and dipstick tube.

34. Refit the wire trunking to the two studs from the injector rail.

35. Refit the ECU plugs. You will find the left hand plug is only just long enough to reach. You may have to loosen the wire trunking to get it on first. Ideally, if you haven’t already made the ECU mounting plate you might want to redesign it so the ecu is mounted slightly further up.

36. Refit the fuel pipes, 19mm nut to the right, 17mm nut to the left.

37. Refit the 58mm TB with the four original bolts and plug back in.

38. Refit the air pipe, breather pipe and temp sensor plug.

39. Reconnect all your brake servo pipe work.

40. Double check everything’s screwed back on and plugged in and re connect the battery. Its been ff long enough now to reset the data blocks probably, so drive nicely for the first few miles to let it all settle down.

41. At this point you can start the car and check everything’s happy.

42. Refit the bumper and any other odds and ends and your done.


Please feel free to update this "how to" of anything you think you can add of importance or find an easier way of doing. Hope its of some help. Adam
You sir are a LEGEND .. ! cheers..

Very well documented and it will make my job easier when I d mine in 2 weeks. I'll be adding a oil catch can when I do mine .. my current manifold has a nice pool of oil and s**te in it.

So how different does it feel compared to the old manifold?
Sorry for the late reply, been very busy this last week. I went to a freinds garage B&J race enginers and he had a pile of old alternators in the back that had come off the donor engines. I just picked up the first one and pulled the supressor off it. It was about 4.2 microfarad 120V rated but anything will do in all honesty. I'm told most modern alternators run pretty noise free without a supressor anyway, but I'd put one on just to be on the safe side, it would be an arse to fit afterwards.

Having now driven the car around for a week the ECU seems to be getting quite settled with the new perameters. At first It was hard to quantify how much differance the manifold had made, but I'm finding that its really smoothed out the flat spot between 2500-3500rpm, It no longer surges at 3500rpm it just seems to pull smoothly right through. The induction noise is very nice, but that could be partially contributable to the dbilas flowmaster and It pulls hard right to the redline but again thats more due to the cams. Its not transformed the engine all on its own, but with the other mods it seems to have been a good part of the package. What we need is someone to do a before and after RR with an otherwise standard motor.
Hi Dave, I sorry but its just not a job I'd like to do on somebody else's car. If I have the time and your local enough i'd come and help out, but I wouldnt like to be responsable for shearing a manifold stud or anything, becouse you just cant predict what will go right or wrong on these jobs.
I just picked up the first one and pulled the supressor off it. It was about 4.2 microfarad 120V rated but anything will do in all honesty.
Do you know what the capacity of the original supressor is?
Here in Germany you can buy supressors at the Bosch service, but they have diffrent capacities: 0.47 microfarad, 2.2 microfarad and 4.7 microfarad.
Osirus said:
I just picked up the first one and pulled the supressor off it. It was about 4.2 microfarad 120V rated but anything will do in all honesty.
Do you no what the capacity of the original supressor is?
Here in Germany you can buy supressors at the Bosch service, but they have diffrent capacities: 0.47 microfarad, 2.2 microfarad and 4.7 microfarad.
I think you can use either a 2.2 or 4.7 microfarad dunno..