fiddlewallop

Hi Guys,

I'm not sure if this fits into the first gen forum topic or not, but I have a 78 Toyota Chinook camper, which I believe is on the body of a 78 Toyota pickup, just with a camper back.

It's a great little rig for adventures and stuff.

But I had a question for you guys.. I have been having a consistent problem with the exhaust manifold. It seems to constantly blow the manifold gasket. I have fixed the gasket 4 different times, and each time I fix it, it stays fixed for about 2 weeks and then it blows again.

I have come to the conclusion that the manifold gasket, or perhaps the manifold, was not designed to accept the amount of pressure that comes from the engine.

So the only way I can think to fix the problem permanently is to weld the exhaust manifold onto the engine block.

Would this work, or would this create serious problems? Someone mentioned that the heat from the engine might transfer to the metal of the exhaust manifold (to a much greater extent) and this would cause problems. I'm not totally sure if that is the case or not. Any ideas?

Thanks!
FW

peow130

Yeah dont do that.
My guess is that your truck has either aclogged cat or clogged muffler, causing serious pressure build up.

stepside trd

Before you do something as drastic as that (which, BTW, I don't recommend), why don't you you try checking your manifold flange to see if it is warped, or your mounting bolts could be bad already and loosening, causing the gaskets to blow. If those don't work, try changing the rest of your exhaust to a larger diameter (say, 2.25") and a less restrictive muffler.

fiddlewallop

Yeah, unfortunately I don't think that's it because it doesn't have a cat and the muffler is pretty new.

peow130

Warped manifold most likely. Pull it, take it to a machine shop, get it flattened, and get it back on the road.

stepside trd

When dealing with exhaust gaskets, I usually install new ones with (permatex) copper spray on either side of the new gasket, regardless of what brand I'm using. Unless, of course, you are able to find all copper exh. gaskets, then you just have to maintain the proper torque on them. In any case, I think your problem lies further down you exhaust, ie... restrictive exh. tubes and/or clogged muffler.....

GeminiFire

Ive put used gaskets on my manifold (now a header) on my 22r, which should produce more pressure than a 20r i would think. plus ive had a 20r and ive never had any issues like that. i do however have to replace the gasket from the other end of my header to my pipe(where the 3 triangulated bolt pattern thing is) about every 6 months. i think next time ill invest in the copper one.. but i would say that your manifold is warped, so like they said up top, definately get that shaved at a machine shop thats the cheapest and first thing i would do. its probably a good idea anyway.

but yeah, the manifold should ABSOLUTELY be able to handle the pressure without blowing.

83

And sometimes things like gaskets or seals failing is, well...a faile-safe. You don't want that pressure having to cause a more explosive failure because it can't blow the gasket since it's welded. If the gasket is blowing because of too much pressure, fix the cause of too much pressure. These engines were designed to work, not fail. Welding the manifold (I'm thinking welding cast iron to aluminum might be tricky anyways?) is NOT the answer.

But like other people mentioned, you've probably got a warped manifold. Check that out (and while you have it out, make sure it's not full of carbon buildup), and use an OEM gasket and torque wrench when you install it.

fiddlewallop

Ya, I brought it to my mechanic. He said, that the last time I put the gasket on, the studs weren't tightened down enough. There's certain torque pressures you need to adhere to. So he's going to put on a new gasket and tighten them with a torque wrench. Also the intake manifold pipe had a small pin head crack in it from rusting, so I got a new one from the junkyard. I had had the exhaust mani re-planned down by a machinist and my mechanic said that it looked good and flat. So we'll see. Should get it back tomorrow or the next day.

bob200587

Something is warped.

83

Yeah...if you're going to be wrenching on your truck, get a manual! Torque is extremely important. Honestly you have no business doing anything more than oil changes if you don't have a torque wrench, or the experience to know what "tight enough but not too tight" is, which only people with years of experience have a feel for.

fiddlewallop

Arrrg... I had the manifold fixed professionally by my mechanic. It stayed sealed for about 2 weeks, then it blew again!! I don't know what to do about this.

I had the manifold planed down as well. Just not quite sure what else to do. I also had a brand new intake pipe put on from a junkyard.

I'm really starting to side with my original theory, that the exhaust manifold was just not designed to take that amount of pressure. I do not believe I've ever heard a quiet chinook before.

I wonder how much of a health risk it is to have a leak in the exhaust manifold. I guess as long as you drive with the windows rolled down a bit, should be fine.

fiddlewallop

I was wondering, although I had the exhaust manifold resurfaced, maybe the headers need to be resurfaced as well? I was reading some posts on the internet about folks who have had multiple blow outs, and this solution sounded intriguing:

.....
If you get the exhaust manifold flat, and the heads are nice where it bolts up, just use hi temp silastic and no gasket.

I don't use gasket anymore and no leaks on my headers.
....

I'd LOVE to not have to use gaskets, if I could get away without them. I'm so sick of buying them, and having them blow. I've probably put in about 200 bucks just on replacement gaskets at this point.

Could a machine shop resurface the headers?

MercuryMan

yes you could have your head resurfaced, and if you had the manifold done and it needed it-I bet your head needs it too. If anything is warped than it can't make a good seal and heat will get in.

Another thing you could try is next time you put on your gasket take the time to trim away any areas where the gasket doesn't perfectly fit your ports. Attach the gasket to the head with contact cement making sure the bolt holes line up, let it dry overnight. Then stuff some clean shop rags into the ports and use a razor blade to cut away any excess gasket that's intruding and bevel the edge to further smooth out the transition.

fiddlewallop

So, I have now officially had the manifold fixed 8 times. This time, I purchased a "header" and used this instead of the cast iron manifold. This drastically reduced the noise of the truck, however, I am still getting carbon monixide into the cab! How can I tell? Well, for one, I have a carbon monixide detector in the cab, and it goes off as soon as I start up the truck. For two, if I drive for like 15 minutes in the truck I start to feel woozy.

This really sucks, cause I have about 800 bucks sunk into trying to fix this problem, and it's still not fixed. The only thing I can think to do at this point, is have the header planed down (this is the new header, not the old exhaust mani), and I bought this goop from Dow Corning which apparently can be used instead of a gasket, to make the seal. I suppose I could try fixing it this way, instead of using a gasket, but other than that, I'm really out of options. If this fix doesn't do it, I think I'm going to drive this camper out to the middle of a field, attach some TNT to it, and blow it to kingdom come. At least I'll get some enjoyment out of it.

fiddlewallop

Mercuryman, when you said you can have the "head" planed, were you talking about the part of the actual "engine" that the exhaust manifold attaches to?

I get confused now, because my mechanic explained to me that the "header" which is what I have on their now, is just another word for a souped up exhaust manifold, except the "header" has longer pipes and therefore the exhaust doesn't merge into one singular pipe for a longer period of time. BUT, I think this is different from the "head" that you're refering to, which, I believe, is the part of the actual engine where the exhaust manifold connects to. If that's the case, it would seem tricky to me to get that planed down, just due to space restrictions. Maybe it's possible, I don't know.

Because, I think when the machine shop planes down the mani, they just put it on a really large table sander for a couple minutes, and plane it down that way. If they needed to plane down a part of the engine, that would be tricky because they obviously won't be taking the engine out. Not sure how they'd pull that off.

83

Yes, the head is the upper half of the engine, with the valves in it. A "header" is an aftermarket exhaust manifold. Or at least that's what people call them.

The head is aluminum, so if the engine was overheated at some point, it is possible for it to warp. If it is warped, yes, it needs to come out of the engine in order to be flattened, as far as I know.

Figure out if the surface is flat, and go from there.

MercuryMan

In the US we call all aftermarket stuff 'headers' and the usual factory set up is an exhaust manifold. In the UK they call it all exhaust manifolds. So it can be confusing, but they do the same job and are basically the same part, headers are designed to give you better flow in most cases than the factory stuff.

Right, that is your surest method. Buy a new head gasket, remove your head and take it to a shop and they can remove any high points (warpage), if you do this make sure they have your header too and can mod the header if needed after the head is flattened.

But there is another option if you don't want to go to all that trouble. You can determine if your head is warped using a metal straight edge, lay it across the gasket surface and use a feeler gauge to measure the clearances. There shouldn't be more than .003" diff. in a 6" span or more than .006" total difference. You want to measure straight across and on the diagonals.

If it's warped and you're brave you can fix it using an old school technique. Attach your new gasket (with contact cement) to the header or your old manifold would be better if its easier to maneuver in there and coat your gasket with Prussian blue dye. Then very carefully attach the mounting bolts and began to tighten evenly all around as you get close make sure you are going in at the same rate and in small increments. As soon as you began to make contact with the gasket go only a little farther. Carefully back it off and observe where the dye transfered (obviously before you do this the head must be clean and free of oil/grease). These are your high points and need to be sanded down. Place rags in your holes and sand down only those spots. You must go slow in the process and make sure you don't remove too much, and use progressively finer grit as you go. I would still remove the head if it were me just because long hours of leaning over my engine might make me crazy, but it can be done while still in there.

Do you know for sure the leak isn't in your pipe somewhere? I realize you've been having trouble with the header but CO can come in from a leaky pipe as well. You could leak test the system and see where it's compromised.

Oh and don't blow the little beastie up-although I must admit that would be quite a show especially with a full tank of gas-but whatever it is...IT can be fixed.

fiddlewallop

Thanks for this explanation and encouragement mecuryman!

So, today, the gasket on the pipe flange blew (the gasket for the exhaust manifold has not yet blown, amazingly). So, I have two options:

1. Fix the flange gasket with the Dow Corning goop. If I do this, it will tell me how strong this goop really is and if it will actually hold. The down side, if it does blow, it will probably be a pretty big mess to get all that gunk off of the flange.

2. My mechanic said that the gasket for the flange was a pretty thin fiber material. (I believe the same thin fiber gasket material was used on the exhaust mani as well, so it's probably only a matter of time before that blows as well.) SO, option #2 is to fix the flange blowout gasket, with a better, higher quality metal gasket. What type of metal should I use for the flange gasket? Not sure. I guess I'll see tomorrow what options are available at Advanced Auto, for metal gasket materials that might fit the flange.

...

Then, once I replace the flange gasket, in all likelyhood the manifold gasket will blow. I will then have the header planed down by a machine shop, have the flange cut off and welded together to form one pipe, and consider having the the head taken off an planed down. Although having the head planed down is going to be mucho $$$$. There's a lot of work involved with that, and if that's necessary, I will seriously be consider the TNT option, again.

MercuryMan

You are welcome. I have had several projects over the years that I thought would beat me, but eventually I overcame the issue and got it fixed. Although I did once take a computer outside and throw it off a very high wall and then go and beat it up with a 20lb sledge-but it had it coming!

If your final option is that expensive, then I would just buy a replacement head from a salvage yard, but obviously take your tools and check it out first if they haven't. A used head wouldn't cost $$$$.

Best of luck with your plan, solid copper has long been an upgrade choice for gaskets in high horsepower plants, and more recently a new type has come out called 'multi-layer steel' or MLS gaskets. Racing engines are using the MLS these days, they can put up with double or greater pressure than stock parts.