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  #1  
Old 03-27-2006, 05:56 PM
 
Join Date: Mar 2006
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Default Intake Manifold Gasket replacement


Hi all -

I've a 1998 Blazer, and just found out that the intake manifold gasket is leaking

There's coolant coming from the front of the block, maybe from the water pump as well so I'll replace that. I've grounded the vehicle until it's done - the coolant's clear now and I want it to stay that way! I'm in need of hints...

* How difficult a job is it?
* Do you need any special tools?
* Mr Haynes gives almost no clues. Is the Chiltons manual worth getting?
* Do you need to drain the oil?
* My Haynes says drain the radiator. Surely, drain the block, too? I'm thinking of replacing the alarmingly bulgy lower radiator hose while I'm at it.
* Do you really have to remove the fuel rail? If so, do you have to depressurise the system?
* Step by step would be great!!!

Cheers in anticipation

Neil
  #2  
Old 03-27-2006, 07:58 PM
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Default RE: Intake Manifold Gasket replacement

Don't know how difficult it is, but I'll let you know when I do it in about 2 months (or sooner if I get time).

Don't think there's going to be any special tools required...

Chiltons would probably be worse.

Shouldn't need to drain the oil, but wouldn't hurt.. That is unless you were getting coolant in the oil, then get that stuff out QUICK!

Draining the radiator should sufficiently drain the block out. To completely drain the block, remove the coolant drain plugs on the side of the block.

Fuel system must be depressurized and removed. (it's under the upper plenum). Also, the Distributor must be removed. Make sure to mark the distributor body with the rotor position before pulling it out. This is for alignment purposes during reinstallation. Also, mark the base of the distributor to lower intake manifold with a dash so you know where the body is supposed to be in relation to the block as well.

I'd have to have more time to run through a step-by-step process for you. We'll see what I feel like after Firefighting practice tonight...
  #3  
Old 03-28-2006, 01:40 AM
 
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Default RE: Intake Manifold Gasket replacement


Thanks for that - good stuff. I take it that to depressurise the fuel system, I pull the fuel pump fuse, then run the engine until it dies? Hum. Mark the distributor. I'm going to need a ladder...
  #4  
Old 03-28-2006, 02:41 AM
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Default RE: Intake Manifold Gasket replacement

No, pulling the fuel pump fuse will only prevent the pump from activating. You must push the shrader valve to release the fuel pressure.
Quote:
(it's under the upper plenum).
You may have to remove a plastic cap on it to access it. Remember to put that cig out before you work. and have a rag ready to catch/absorb the fuel that will come out. When it's pressurized with the atmospere, it'll barely trickle out.
  #5  
Old 03-28-2006, 08:03 AM
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Default RE: Intake Manifold Gasket replacement

Pulling the fuel pump fuse or relay will do the same thing as pushing the shrader valve. It's also good insurance to make sure that no one inadvertantly pressurizes the system while it's apart. If you attempt to start the vehicle with the pump disabled in this way, it will depressurize (won't run though). Still check the shrader valve before cracking the system.

You'll need to pull the lines apart at the back of the motor before pulling them out of the SCFI module (behind the throttle body). The throttle body will have to be removed before removal of the upper plenum. Then the Distributor. Next is all of the misc. stuff that is on top of the lower intake. Last is the lower intake. I'll try to get a more detailed how-to, with torque specs, together tonight if I can.
  #6  
Old 04-03-2006, 12:06 PM
 
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Default RE: Intake Manifold Gasket replacement


I've started the job - trying to find a wrench small enough to undo the fuel lines at the rear of the engine. I've found some good instructions:

http://aarc.epnet.com/application/88...e_Manifold.htm
  #7  
Old 06-08-2006, 05:54 PM
 
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Default RE: Intake Manifold Gasket replacement


Been a while - realised I never followed this up. This job took me a three weeks, mainly because I was working evenings (and only about three a week, I'm busy) and being careful and methodical. Things I learned included:

1) This is the kind of job that having zip-lok bags for the fasteners associated with each component, carefully labelled, is essential.

2) PB-blaster is wonderful. It doesn't just loosen things, but cleans up all those oily surfaces easily, too.

3) Take lots of digital photos, from a number of angles of how various hoses etc route before removing them.

4) One of the painful bits is undoing the fuel pipe bolts - you have to remove the alternator first (mark it carefully) and then you need two opposing wrenches to unlock the two nuts. Then finally you can consider unbolting the bracket.

5) Take careful note of the order of the o-rings on the fuel lines where they stick into the injection manifold. Check inside the manifold - one or two o-rings might have stayed inside. Some of those o-rings might die on reassembly, so consider getting a set of replacements.

6) You don't need (on a 1998 blazer) to remove the power steering pump, just take off the air conditioning pump and put it out of the way on the other side of the engine, and then remove the large aluminium casting that it sits on. Marvel at the unfinished quality of the casting. You'll need a pulley puller (hire from autozone?) to remove the p/s pulley.

7) It is not necessary, but useful, if you remove the alternator too. Removing the clip holding the wiring bundle to the side of the alternator is the hardest part of this operation.

8) Work very fast when applying sealant and reassembling the manifold - it dries fast, especially in Texas. Especially, don't go off to help your wife work a tap and then come back to find the sealant's all dry and you've got to remove it again...

9) A standard torque wrench isn't really suitable for the lower manifold bolts - the torque is too low. I have to admit that tightening them to only 28 in-lbs (or whatever it was) to avoid crushing the flimsy plastic gasket is not confidence-inspiring - you can almost overtorque them by hand!

10) Getting the fuel lines back into the injection manifold is a bit of a pain.

11) Be careful about the routing of hoses and wiring

12) When putting the alternator back in, you might find it doesn't seem to seat properly, even though it appears to be aligned. What I discovered is that every time I tried to reseat it, the oil pump key (which is on the tip of the shaft) rotates a bit. So you'll find that a little clockwise from the correct position seats, then a bit more, and a bit more.... work your way round until you get to where you came from and it seats correctly.

13) Once you're all done - change your oil! Despite your best endevours, it is unlikely you'll have escaped getting bits into the oil.

I hope this is useful....
Old 06-08-2006, 05:54 PM
 
 
 
 

Tags
1998, 2000, 98, blazer, bolts, chevy, cost, depressurize, forum, gasket, intake, manifold, repair, replacement, torque


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