Morning Everyone,
I was on here the other day and found a very descriptive procedure on replacing the lower intake gaskets. I can't seem to locate that thread now.
It was very nice with pics and certain tools needed.
Can anyone post a link or something?
Thanks

 

Found it, thx anyway

 

Check this site as well, very helpful

How To Replace Intake Manifold Gaskets On A GMC Jimmy 4.3 Liter V6 To Fix A Coolant Leak - GM Truck Engine Repairs

 

That site is an excellent "How to" for this job.

A few additions, and one recommendation.

The bolts for the lower manifold have to be tightened in proper sequence, in three separate steps. The actual torque specs are 26 inch pounds for the first step, 106 inch pounds for the second step, and 132 inch pounds for the final step. I'll see if I can scan or photograph the diagram with the order, but you criss-cross, working from the center out.

The bolts are "replacement recommended." Personally, I'd never reuse the original bolts, and I strongly recommend stainless steel replacement bolts. ARP makes a set specifically designed for this application (ARP part # 434-2002), or you can get 8 good quality stainless bolts, 5/16-18 x 1.5 inches long, with smooth flanged heads. Install the bolts with aluminum anti-seize on the threads, and on the bearing surface of the bolt head flanges. Anti-seize (not thread locker) is even more critical if you use "stock" or aftermarket replacement bolts that are not stainless.

 

Well I wasn't going to replace the bolts but I may now. It seems like I've seen both methods discussed here. I may be mistaken but I thought someone said use medium thread lock, someone said use a good sealer and you recommend anti seize.
That makes me a little confused
Later

p.s. Thanks for the info and the links!

 

Well, here's more than you want to know about the three choices.

• Anti-seize lubricates the threads and bearing surface of the head (when applied to those areas), it significantly reduces the chances of galling, and it somewhat reduces galvanic corrosion and chemical corrosion in the event of leakage. Since it also lubricates things, the bolts will be slightly tighter (turn slightly more) at the same tightening torque, compared to dry installation. This slight additional clamping generally helps the gaskets seal. Many manufacturers specify anti-seize for intake manifold bolts.
• Thread locker can reduce galling and can also reduce galvanic corrosion, but that's not it's main purpose, and the effect is less than with anti-seize. It makes the threaded joint 'stickier' and can slightly reduce the clamping force at the same tightening torque when compared to dry installation. That can work against you for gaskets sealing properly.
• Sealant is almost always a bad idea in threaded joints. It is much 'stickier' than even thread locker. The attraction is that you hope it will keep the Dexcool out of the threads and prevent total seizure of the bolt when the gasket finally does fail. At the same time, though, it significantly reduces sealing of the gaskets by reducing clamping force at the specified tightening torque, making the leak more likely.

The best approach, IMO, is to use the right gasket (the one with the metal substrate) so it won't leak, and get the fasteners tightened down to spec with the best clamping force you can achieve. Anti-seize does all of that.

 

alrighty, I like those explanations. I've been a machinist for over 35 years now and the anti seize makes sense. One more question...I think,lol, should the lower intake gaskets be installed with both surfaces clean and dry...nothing but gasket other than each end where you have to use the tube of sealant?

 

The factory service manual, at least for my 99 blazer, specifies that thread sealant be used for the intake manifold bolts.

 

Exactly, a clean and dry mating surface is very important. Alot of the members here recommend the felpro MS98002T kit for the 4.3, it has a metal core and is significantly more durable than a plastic gasket. That kit includes both intake gaskets, valve cover gaskets, throttle gasket, upper plenum gasket, valve cover grommets, an oring for the brake booster vacuum connection at the upper plenum, an evap purge valve o ring (viton), and two orings for the fuel feed/return pipes at the firewall. I installed this kit last month along with an upgraded spider. Also completed a full tune up as well.

 

That is exactly the kit I have. I just ordered the ac fuel injector kit and a new upper plenum, mine has a crack in the rear passenger corner.
Did you see a nice improvement on performance with the new parts?