Removing Manifolds

[Chris Cahill]

So I am in the middle of my desmog on my '84 and changing my manifold gasket, due to an intake leak (loud whistle) when hot. Found the likely culprit - one of the manifold bolts was not even hand tight.

Anyway, the manifolds are stuck onto the head pretty good. Starting to move a little but it looks like I may need to drop the front exhaust pipe entirely in order to get them off. It has been a while since I did my '87 and that one wasn't stuck.

Wondering if most people drop the exhaust pipe to remove the manifolds, and whether the cross member has to come out in order to do so?

 

[brett76]

if you just unbolt the exhaust at the flange so you can get it out. i never usually even do that but since your doing the intake you have to take the assembly out completely. are you sure you got all the bolts? if you are just use a dead blow hammer or smack the manifolds or a piece of wood and a BFH

 

[Chris Cahill]

Yea I got all of the bolts. I verified by inspecting several times and counting against the new stud and bolt set I received from Specter. It has been 10 years since I did my other one but there are 8 total as I recall.

Thanks for the confirmation - I was worried about damaging the threads on the exhaust manifold-to-pipe studs but I think I just need to continue with the BFH/sawed off broomstick. I should remove the front pipe anyway to saw off the air pipe and weld it shut, but I was just going to have a muffler shop do that later.

 

[Slow Left]

It is possible to remove the manifolds from the vehicle with the EGR system still mounted to the manifolds...but you must remove the two bolts that hold the EGR cooler to the engine block...and you must also remove the PS pump from the PS pump bracket and slide it forward out of the way.

It is also possible to remove the EGR system from the manifolds with the manifolds installed, but you must remove the shield on the DS frame rail (3 bolts, one up on the cover over the link between the steering box and steering rod)...then the EGR system drops down and comes out underneath the vehicle...

If you loosen the 3 nuts that hold the exhaust downpipe to the exhaust manifold, and also loosen the bracket that holds the down pipe to the side of the engine block, there should be enough wiggle room to pull/install the manifolds without having to remove the downpipe from the front of the CAT. But on re-installation, be careful not to mess up any gaskets...go real slow.

 

[Chris Cahill]

Thanks. Appreciate the response. I have the EGR system completely disconnected and dropped, waiting till the manifolds are out to pull it rather than removing the shield. Having the manifolds out will also make the air pump removal very easy. I did loosen and move the bracket holding the pipe to the engine, but the pipe still doesn't move much. I am sure I will get it with enough persuasion and patience.

Last time I did one I used the SOR manifold stud kit, which is nice because all of the bolts except the 2 on the ends are converted to studs that hold the gasket in place.

Loving the desmog process - very therapeutic to get rid of all that crap that has been in my way for so many years.

Keeping my fingers crossed that the manifolds will come apart OK so I can install the heat riser insulator and new gaskets. So far I have had zero trouble with frozen bolts, nuts, air rail etc. Thank you PB Blaster.

 

[Slow Left]

Remember that the intake manifold is aluminum and the exhaust manifold is cast iron...so if you are going to put force on the manifolds, I'd do it to the exhaust manifold for fear of cracking the more fragile aluminum intake manifold...

When reinstalling manifolds after having taken the manifolds apart to put on new heat riser shield and gaskets between them, I fasten the 5 bolts that hold the manifolds together VERY LOOSELY, then position the manifold assembly into position on the engine on top of the down pipe and with the new gasket between the head and manifolds.
Then I LOOSELY fasten in all the manifold-head bolts (following torque sequence) and the three nuts that go to the down pipe.
Then I bring in the head-manifold bolts/nuts to finger snug (following torque sequence), then same with the down pipe and then 5 bolts holding the manifolds together.
Then tighten down the head-manifold bolts/nuts, followed by down pipe to torque...and lastly tighten down the 5 bolts holding the manifolds together.

 

[Chris Cahill]

Yea I was dreading seeing a big crack under the carb mount like others have had but mine doesn't appear to have any cracks. I have been careful with it and will take my time.

Great info on the reinstall - I was planning to leave the bolts holding the manifolds together loose but hadn't thought of tightening the exhaust pipe before those. Probably a good idea.

I am using the Remflex gasket because I had great luck with it on one of my other 60's. Changed it in 2001, no leaks and it still looks like the day I put it on.

 

[Slow Left]

Cool. Good break on the crack-free intake...

Sounds like you've got the right plan. I agree, I tend to dial it back to real slow...especially if it is one of those frustrating jobs like the manifolds are...since you can anyways only act one step at a time...no need to let the mind drag you ahead in time/steps...

 

[Chris Cahill]

Roger that.

I just saw a thread where someone was having the same issue (stuck manifolds) and he said they came right off after he removed one of the center studs. I will try to see if I can get 2 nuts on them and get them out. That would certainly make things easier.

 

[Output Shaft]

I had to remove 2 the exhaust pipe clamps all the way back to the CAT to allow the exhaust pipe enough leeway to easily swing down so the 3 manifold studs would clear it. No big deal. It could then be held down and out of the way with a strap.

Often the intake/exhaust manifold is a bit warped if it is 20 yrs old or so. It may look flat but often isn't. Running a high quality straight edge along the corners as shown in the manual can reveal if that is so.

I have been told by "those in the know" never to take apart a manifold assy. unless you plan on having the assembly resurfaced again after it is bolted back together. Apparently (or so I was told by those who knew) it never quite goes back together flat again once it is separated.
That is what I was told (& experienced) but others may have had better luck. Just a head's up.

I have not had good luck with the two small manifold bolts sold by anyone but Toyota. I would strongly recommend using the two smaller Toyota manifold bolts that go in the far ends of the ears at each end of the manifold. They are not normal 10mm bolts. They are designed for the heat of the manifold and strengthened. I had one of those smaller "aftermarket" manifold bolts installed and the head of the bolt sheared off when tightened the 3rd time at the specified torque... and that bolt is a bitch to replace...especially when the hex head is gone

fred

 

[Chris Cahill]

Finally got the manifolds off tonight after a lot of tapping, jiggling and tugging. They were stuck on the center studs but I could not get the studs out because there wasn't enough room for 2 nuts to bite. I got them out afterwards with no problem though.
Now for my dilemma. The bolts holding the manifolds together are very tough to move and load up immediately when I try to loosen them. I am afraid to force them but have the PB Blaster working on them now. I really want to put in my new SOR heat riser insulator but I am going to stop and sleep on whether I really want to risk breaking one of these bolts or stripping threads.
Before my luck runs out on these 30 yearly bolts I have been removing, it may be better to just have them machined as is.

 

[Output Shaft]

Installing a SOR insulator plate is debatable. Some swear by it, other very reputable shops say don't use it, as the intake needs the heat to atomize the wet fuel in the long intake runners. I don't know. But if the SOR plate isn't used you may still want to replace the internal Toyota split insulator anyway... as that thing is probably on it's way out if it is still in one piece at all... so the thing should come apart regardless... if you have a machine shop that knows how to machine it flat.

Find a machine shop that knows this manifold and has the jig and experience to machine it before you break it in two. If you don't know of one, there are a few experienced machine shops in CA that have worked on these and know what they are doing. You could ship it to one of them if there is not a shop in your neighborhood.

just a thought..

fred

 

[Chris Cahill]

Thanks, that is valuable info. Surprisingly the stock insulator and heat riser are in remarkably good shape. Still pondering whether to attempt those bolts again. Pretty sure I am looking at one or more breaking off.

 

[Slow Left]

Surprisingly the stock insulator and heat riser are in remarkably good shape.

Is that by inspection through the port in the exhaust manifold...by rotating the heat riser flap out of the way?

Still pondering whether to attempt those bolts again. Pretty sure I am looking at one or more breaking off.

That is a tough call...one that you're gonna ultimately have to own, since the implications either way might be affected by how your specific circumstances allow you to respond (as OS points out about getting the manifolds planed together as an assembly).

One way to look at it is to list out the scenarios of what could happen and see if you have access to the resources (time, money, parts and local machine shop expertise) to address each possible scenario...and that gives you an estimate of the cost of failure and whether or not you can 'afford' to take the risk.
Then weigh this risk against the possible costs of not acting (in other words, reinstalling manifolds with current heat riser shields and gaskets)...

If I remember correctly, there are 3 bolts on the top (intake manifold side) that screw into threads in the exhaust manifold. Exhaust manifold is cast iron, so stripping/breaking a bolt here might not be as costly as stripping the threads of the two underneath bolts that thread into the aluminum intake manifold...just something to bring up with the local machine shop...

 

[Chris Cahill]

Yea the flap rotates easily and both it and the stock insulator look great. No soot, no rust, just kind of a golden brown color.

I am thinking about just taking the whole assembly to a machine shop to go over my options. Maybe have them take them apart. Then I would have to bring them back home, loosely bolt together, bolt (not too tight) to the head, tighten the 5 mating bolts, remove and take back for machining.

All part of the fun.

 

[Slow Left]

Oh, and FWIW, when I removed those 5 bolts that hold the two manifolds together, I used a box end wrench on the head of the bolt, had the manifold faces flat on the cardboard covered ground (for stability so that I was striking down on the wrench to break the bolt free) and used a single deft blow with a rubber mallet to the other end of the wrench (while holding the box end securely in position on the bolt head with my other hand) to break the bolt free...

 

[Slow Left]

Then I would have to bring them back home, loosely bolt together, bolt (not too tight) to the head, tighten the 5 mating bolts, remove and take back for machining.

Yes, I was going to make this point too, but I guess only if you had decided to take the assembly apart...but yeah, that's how I would do it too...! If you use the old gasket when you do this it might save the new one from getting beat up and allow the faces of the manifolds to find their old positions...maybe?

 

[Chris Cahill]

I like the hammer idea - maybe I will just go for it. What's the worst that can happen? Hmm - trying to find a good set of 30 year old, discontinued manifolds I guess.

The old gasket was toast and fell apart so I was just going to to the head without any gasket.

 

[Slow Left]

I am thinking about just taking the whole assembly to a machine shop to go over my options.

Sounds like a good idea, too. If the guy at the machine shop follows the logic of your options and risks as you lay them out (as you understand them) to him and if he supports them (says yes, if that happens, we have the capability here to fix it by doing this...) then you've got both a plan and an ally...

...and if he makes suggestions on how to improve your plan, then you've got an exemplary ally...

 

[Slow Left]

I like the hammer idea - maybe I will just go for it. What's the worst that can happen? Hmm - trying to find a good set of 30 year old, discontinued manifolds I guess.

Yeah, I guess the worst that could happen would be having to replace the whole manifold assembly. You might be able to price that cost out by how much they go for here on MUD in the Classified section or maybe even new on one of the Toyota overstock websites...and then factor in the down time for how long it will take for them to arrive...

But if you are going to separate them, then that takes a series of steps (a procedure). Each step has a risk.
For example, of the 5 bolts holding the two manifolds together, there are basically two types.
1) threads into cast iron exhaust manifold
2) threads into aluminum intake manifold

and there are three 'failures' that could happen during removal:
1) head strips
2) bolt breaks
3) threads in manifold housing strips

Take each combination of scenarios and see what cost needs to be incurred in order to remedy the problem afterwards.

For example, a broken bolt that threads into the exhaust manifold won't stop you from separating the two assemblies (since the threads are only in the bottom part - exhaust manifold- so the intake manifold will slide over the broken bolt now that the head is gone), but once they are separated you are going to have remove that broken bolt, probably by drilling and retapping or helicoil.

Then repeat for all options...since the cost of doing this to the aluminum intake housing might differ from the cast iron exhaust...yada yada yada...