'89Lariat

I've decided to replace one of my exhaust manifolds soon, it has a crack that goes all the way through (so it will come apart in two or more pieces, most likely). Anyway, from my reading here's what I plan to do for the repair. I have a few questions along the way as well. Please let me know if I am missing anything:

1) Spray all bolts on the manifold with ample doses of WD-40 or similar, multiple times, letting it soak in really well for at least a day or two.
2) Remove all bolts, remove old manifold.
3) I'm not sure if I currently have a gasket where the manifold meets the block. The gasket at the store was all connected in one piece, whereas the manifold has four separate tubes. So if I currently have a gasket, wouldn't I be able to see gasket material between ports of the manifold?
4) Replace manifold with a new one, use a gasket if needed. It seems like this will be required.
5) Install all new bolts? Is this necessary, and will an ordinary auto parts store have the right kind? I plan to use Loc-tite on the bolts, is there anything else I need to do to keep them from backing out?

Looking at it, this should be an easy repair. But the problem is, it always seems to be the "easy repairs" that end up taking me a ton of time. If anyone has recently done headers or manifolds, what pointers do you have? Since my truck is down for maintenance anyway, I figure I'll have time to let the WD40 soak in and loosen things up.

One final question, since my manifold is bad, and has been for quite some time, I think it has probably affected my catalytic converters and/or O2 sensor. How should I know if these need replacing?

Just call me Sean

iTrader: (1)

You need to use a gasket, it requires one. I don't like to use Loctite on exhaust parts. You will most likely break a few downpipe bolts, but they have them on the shelf at the parts store. You don't need to use new bolts if they're in good condition. I clean them up with a bench grinder wire wheel. You can get stainless steel bolts at Lowes, I used them on my LeMans. There are also locking type exhaust bolts available if you're worried about them backing out.

wde3477

1) Recommend PB-Blaster or other suitable true penetrating oil.
2) OK - but go slow and easy with the torque - don't want these bolts snapping off. If the penetrating oil has done its job, shouldn't be a big issue. Time is your friend with penetrating oil.
3) Some disagreement exists on using a gasket. Mine didn't have them - just metal-to-metal contact. Seals OK. The Chilton's book recommends a light coat of graphite grease on the sealing surface. Be sure to follow the proper tightening sequence.
4) Yeah - it would seem to be such a waste to bolt the old one back on after all this. :-)~
5) Eh, I would have a look at the bolts that came out - if they're OK, I'd go back with them. If not, then hit the parts store up - likely not going to get the exact bolt, but should be close enough. JMO. I would also suggest to chase the bolt and block threads with a tap-and-die to ensure proper torque values. I re-used the lock-washers instead of Loc-Tite.

Been a while since I've replaced mine - but don't recall anything too difficult, just a bit time-intensive. A 3/8" socket set with u-joint along with 3" and 6" socket extensions would be helpful. A 1/2" drive with 18" extension was handy for undoing the exhaust pipe flange bolts, coming up from underneath.

Haven't heard of a cracked manifold messing with the cat or O2 sensor - not that this hasn't happened. Suggest if your O2 sensor has any significant age on it - may as well change it out too. For the cat, my approach is to listen and to feel for the pulses coming out of the tail pipe as indicators. When a steady flow without pulses is felt, or the engine labors to get into the higher RPM ranges under load, the cat is the usual suspect - if it turns cherry red and one knows the engine isn't running rich, another good sign.

mitchalvin

Use a lock washer and antisieze on the treads, this way if you have to remove them again you more than likely will be able to. Loctite breaks down with heat so it is a pointless to use on exhaust parts.

'89Lariat

Okay, shifting course slightly, here's the current take:

No more Loc-tite, in case I do want to do headers some day. I'll try a lock washer and anti-seize as suggested by mitchalvin.

Few more questions, lettered instead of numbered:
A) If my truck currently has no gasket, do I still have to use one? Is the graphite grease meant to supplement or replace the use of a gasket?
B) Is WD-40 not considered a penetrating oil? What about liquid wrench, I use that from time to time as well.
C) Do I need a torque wrench for this project? Or do they just need to be good and snug?

grilljames

if ur worried enough to use loc-tite get ur self a set of stange 8 lockin bolts. thats what i used. as ur soaking the header bolts it wont hurt to tap the heads with hammer to pre shock them.

'89Lariat

I think I'll just reuse what I have, as long as I don't break any. I'll keep my eye on it for a few weeks, and tighten them as needed. If they do loosen up regularly, I'll pursue another solution.

Just call me Sean

iTrader: (1)

Yes you need the gasket. Flat washers work better than lock washers as they have more friction area. WD-40 will work, but PB Blaster is better. When you spray the PB you can almost hear the bolts backing out themselves. Torque wrench isn't really necessary.

dr_bowtie

if you use the factory gaskets bolts wont come loose...

all bolts should come right out except for the flange bolts...beings the manifold is broke just snap them off...

'89Lariat

I'll still have to get them out of the flange, right? Will that be difficult?