4Runner: Exhaust manifold gasket

Factual Questions
1

You guys have been really great so far so let me pick your brains again, if I may.

My exhaust manifold gasket leaks. It’s a Downey aftermarket header. It leaks on the passenger side, rear-most cylinder. It’s mostly annoying but I know that back-pressure is very important to this engine so I assume I’m losing some gas mileage to this leak and stinking up my engine compartment.

I ordered the new gasket from Downey and got the bottle of Copper-Coat that they suggest I use.

Now what?

I’m staring at it - my original plan was that I should be able to pull the bolts, scrape the old one out, wiggle the new one in, and be done with it. The idea seems still pretty sound except I can’t figure out how to get the lower bolts out of the header, the pipes are in the way. Is there such thing as a right angle ratchet?

There’s some emissions control things in the way, they look removable. I assume there’s sufficient play in the exhaust pipe that I should be able to pull the header back enough to get the new gasket in.

I would think thread-lock on the bolts wouldn’t survive the heat.

Any suggestions or advice that doesn’t require me to pull the engine?

2

Think about it; have you ever seen a truly happy mechanic? Now you know why not.

They do make right angle ratchets, but they tend to be pretty poorly constructed and may break on you (Working on motorcycles, I quickly learned that Skewdrivers will pop apart but can be easily put back together.) Maybe someone has a better suggestion, but you may need to just go at it with a combination wrench, possibly moving one twelfth of a turn at a time. If you have to use the open end, you can gain a little by flipping the wrench over for every other turn.

Ratcheting box end wrenches exist. I haven’t used them, but some are probably better built than others.

I’d use anti-sieze on the bolts, following the Downey’s recommendations. The fasteners shouldn’t back off once they are properly torqued. That said, the bolts probably don’t have anti-sieze on them right now. They may come out without breaking, but be ready in case one does.

3

If you look up pain in the ass in the automotive dictionary it says see headers/see trying to keeps headers from leaking. :wink:

Headers it seems are designed to leak. Repeatedly. Either that or they are some of the worst designed pieces ever sold on the automotive aftermarket. Your choice. Me, I vote for all of the above.

OK you will have to be able to remove all the nuts and bolts that hold the headers to the head. You will have to move the header out (along the axis of the head studs) by at least the exposed length of the head studs + the thickness of the header flange. If the studs stick out 1/2" from the header flange and the header flange is 3/8" you will need to be able to pull the header at least 7/8" from the head. You may well find that it is necessary to start the mission impossible music as header are often designed is such a way that this is pretty much impossible. It can be done, but it can be damn difficult.
You may/probably will have to disconnect the back end of the header from the exhaust in order to be able to move the header enough in the correct direction.
Some tips:
When you get the header free, check the header flange for warpage. If it isn’t flat, it will leak again.

If it isn’t real flat, sometimes dual gaskets will help. I have seen cases where guys have used two and three gaskets to get headers to seal. :rolleyes:
I have also seen guys use a factory gasket (metal clad) against the head, and a header gasket against the header. The factory gasket is more heat resistant, and the header gasket is softer to conform to the irregularities.

Use rust penetrant on the bolts / nuts before you try and disassemble them. Maltby and PB Blaster are the two best brands I have found. Maltby is very hard to find. PB Blaster is available at NAPA stores. (Note: the link shows the case price, not an individual can price.)
The hot ticket on the rust penetrant is the night before with a warm engine spray each nut and then come back say an hour later and spray it again. In the AM one more quick shot, and go for it.

Be advised that some of the studs make have developed issues, and may break when you either disassemble or re assemble the header. Unless you are a very good shade tree mechanic, this repair may well be beyond your ability in the car. You might have to pull the head to have the broken stud drilled out. If this happens, have all the studs replaced. It is much better to spend a few extra bucks at the machine shop then have to pull the head a second time. FTR the last time I did an exhaust manifold I had to replace 4 out of 8 studs.

You are correct, Loctite will not lock on header studs, the temp is too high.

USE ANTI-SEIZE on the studs and bolts when you reassemble. for the love of OG if you follow no other advise I give follow this one.

Consider using new factory nuts on the studs. Often times the factory will use a mechanical locking nut on exhaust manifolds to prevent them from loosening and creating a leak.

If it looks like you have to buy an odd ball tool to get to some of the nuts, go ahead and buy it. As I mentioned before, you will probably have to go there again. Several companies make ratching box wrenches with swivel heads, which might be just the ticket for your [del]headache[/del] header

Good luck

4

I think you’ve both convinced me that this is one for my mechanic. He used to own a '91 4Runner and is well aware of their oddities. I’ll think I’ll give him a call and get an estimate.

So the Copper-coat is an anti-seize compound for the studs (little can of stuff, puff-ball applicator on the inside of the lid, viscous & smells strongly of acetone)? Downey’s quickie advice made it sound like an addition to the gasket itself. I did some googling and found copper anti-seizing compound, too, so I’ll pre-admit to some confusion on this.

Luckily, except for the first bend in the exhaust pipe, it’s all clamped, not welded so it’ll probably be easy enough to loosen up. (The clamp never did seem able to stay connected to the header’s tail end. I had to get it welded.)

One problem for him, that engine gets hot, hot, hot. It’ll be hours after I drop it off before he can touch it, even with the 4 mile trip to his shop. Gonna mess up my day, no waiting for it to be done. Maybe I’ll drop the new u-joint with him, too. Give him something to work on while the engine cools.

5

Read the label. Coppercoat is a gasketing adhesive. Copper coat is also a type of anti-seize.

Probably a good call letting the pro do it. Can you drop it off one night, with the understanding he will do it first thing in the AM when the engine is cold?

6

In case I was not clear these are two different products for two different problems. I did a Google search on copper coat and came up with a page describing installation of Downey headers on a car where the copper coat was a gasketing adhesive.
Read the label.

7

''sok - yoiuy were clear enough.

I’ll just give the can to my mechanic along with the gasket. I guess I’ll encourage good behavior and give him a tube of the anti-seize, too.

Downey’s page says they shipped new studs with the header kit - the stock ones are too long. Perhaps the guy that installed it used the right stuff.