So after disassembling the exhaust manifold on my shiny new turbo 740 wagon, re-assembling it, and then getting it going...I discovered something truly horrible: one of my manifold studs was fudged. it was just plain not sticking to its happy little hole and slid right out after being torqued down.

Now, I just don't have the time to take everything apart again, and I do not think it is in my best interest to drive the car to a shop with a leaking manifold gasket (it'll burn right through and leave me with another shot gasket needing replacement, right?)...

so my question is...is it possible to install a helicoil into the head with the manifold still attached by the remaining seven studs and nuts?

Am I...nuts...for asking? *rimshot* *tomato to the face*

I'm rather desperate right now and need this car working on a timely basis, and I just do not have the capacity to disassemble it again to tap it for a larger stud.

Though, if I find the time to do it and decide to get it tapped for an M10-1.25 stud, where would one go about buying a stud of said size that would not become weak under high heats, such as those created by the turbo?


Edit: I guess the question is asking is not whether or not it's possible to install a helicoil in the head, but if the exhaust manifold hole is large enough to allow it? I was just thinking, though, that one only needs a tiny bit of grinding to enlarge it fairly well, so I suspect that it's probably nothing too difficult, actually.
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1984 240 DL, 1987 740 GLE, 1989 740 Turbo Intercooler, 1990 740 GL, 1993 850 GLT

I am just posting back to report...

Success! The helicoil bit worked absolutely perfectly (After a little modification to the tool to get it to shove the insert far enough in). It's fully torqued down, and not the tiniest bit of exhaust is coming out.

However I have a little bit of a new problem. It turns out the oil return line from the turbo lost its o-ring somewhere between bolting torquing the turbo down and test driving the car just now, and so now i'm losing a substantial amount of oil. I'm still in the same boat that I don't have the time to undo the manifold and such, and also JUST missed the parts counter's hours at my local dealer (DAMN!), so could I be able to get this patched up temporarily with some form of silicone sealant until either tomorrow or monday?
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1984 240 DL, 1987 740 GLE, 1988 740 Turbo Intercooler, 1990 740 GL, 1993 850 GLT

Yeah you can do that. Clean that off real well with something like carb cleaner or brake cleaner, and apply red or blue silicone around it- it's not pretty but it'll get you to work tomorrow. Let it sit all night if possible to allow the silicone RTV to set up.
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Rob Bareiss, New London CT ::: 87 244DL- 249K, 88 245DL- 181K, 84 242DL, 89 244DL parts, SOLD: 86 244, 88 244GL, 87 244, 91 244, 82 245T, 88 744GLE, 86 244

Gave it a try, and so we'll see what happens!
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1984 240 DL, 1987 740 GLE, 1988 740 Turbo Intercooler, 1990 740 GL, 1993 850 GLT

On further checking I find there is plenty of room in the exhaust manifold ear - the holes are .440 except for the locator ear top of port #3. The helicoil that fixes M8 requires a drill diameter .328. You might have to cut the 21/64 bit to get it head on with a standard drill motor w/o resorting to a right angle as friend werick warns, but that muchly depends on which stud is stripped. Since stud is not broken in hole, drilling and tapping should be effortless.

Helicoil (not TimeSert)is the recommended fix per Volvo's manual; done all the time and if you drill straight there's nothing to harm surrounding the tapped hole. If you decide to fix w/o 8mm helicoil, make sure it is hardened stud or bolt and not all-thread or similar. Turbo uses different studs vs. non turbo per parts manual.

Hi Sanfam:

Are you sure the head is stripped? What I would do first, is get the appropriate tap and try to clean it out. Then try to screw a stud or bolt in there and see if it holds.

Another possibility is drilling and tapping for the next size (American or metric). We used to call that a "jury rig" in the navy. This might work with the manifold in place. Works in a pinch, but makes it non-standard. You might not want to do that to your shiny (New for you) 740.

With a Helicoil, you have to drill the hole quite oversize. Then tap it for the Helicoil. I'd do some reseach first to see if you have enough meat, in that area. So you don't go into a water jacket. IMHO I don't think you can do that with the manifold in place. As the manifold hole might be too small to accept the larger tap and helicoil.

Even with the manifold off you might have a hard time getting a drill in there. You might need to use a right angle drill.

Good luck

I was thinking back on the drill bit for the helicoil tap that it would be small enough to clear the manifold's ear, but whether it might not be centered well and interfere is a question you'll have to see for yourself. You might have to loosen all the others and risk wasting your gaskets. On the other hand you might be surprised how much time you might buy with only one stud before needing to do it all over again. Easier to use the coil and stick with the original stud size.