So - I am under the car doing a valve adjustment this morning and notice something troubling. No sure why I never noticed before but one of the #1 exhaust head bolts is gone. I assume its been gone for as long as I've owned the car. The PO had the motor rebuilt within a year of selling the car to me so I guess it snapped then and the builder never said a word.

So my question is what is the risk of running the car like this? Keep in mind its must have 25k miles on it with the bolt missing.

Should I park it and replace? Drive it? Use this as an opportunity to by a Raby kit with new heads?

Let me know.

T

you need an exhaust stud.....

otherwise i guarantee you have an exhaust leak

Yeah no doubt I have a leak, known that for some time, I just didn't know the source until today.

Thoughts? Whats the risk?

Thanks

T

remove heat exchanger and drill/tap for a helicoil ???

jim

You may have lost that recently. If really was gone 25K miles ago, the head is history--not even worth considering saving. Exhaust gases, when they leak like that, will erode the aluminum head--seriously erode it, and probably the top of the heat exchanger and the gaskets too! But by that point, the leak would have been really LOUD and the engine would be running really oddly...

Pull the exhaust and inspect. If there isn't any erosion (yet!) count your blessings and get a new stud in there. Which will likely involve a helicoil or time-sert or similar thread repair technique, but that's less spendy than buying a new (or new used) head!

--DD

Okay - I am finally going to get around to replacing this stud. Additionally I am going to replace the fuel lines and speedo cable.

The main question I have is the stud replacement. If I helicoil do I need to put in an OEM stud (8x53 for a 1.7) or would I use something else? I've never used a helicoil so I am just not sure.

Thanks

T

Trevor, have you been able to inspect to see if the stud is broken off or just completely backed out. If it is completely backed out you can just replace it with a stock sized exhaust stud and nut.
Might not be as bad as you think.

Hi Dan, Thanks for the note. I believe it is broken. Either way, I assume I'll need to order a stud from Pelican (or other). Does that sound right?

Do you have a 1.7 stud laying around?

T

No, but I know who probably has one...local.

if it is broken you may be able to use and easy out and replace it with stock component.

get under there and get the exhaust off and see what you have then you know what you need to do. Hope it is better than you think.

Sounds good Dan. I'll have it off today or by the latest tomorrow and I'll let you know.

thanks

T

Be gentle with the easy out. I broke an easy out in an exhaust stud trying to do the same job. I ended up dropping the motor and pulling the head to fix the whole enchilada. Honestly, I don't know if there is any good way to get those out, with the motor in the car. I would say hit them with some PB Blaster, but it won't soak down anyway. You can try to get it good and hot before the easy out.

I think I would probably get some good drill bits, and drill the stud out. Start small and work your way up.

Okay, I finally got around to pulling this thing off and here is what it looks like. The threads appear to be stripped and there is no evidence of a bolt.

What are the options? Heilcoil? If so, any recommendation for sizing etc.

let me know what you all think.

Thanks

T

timecert?

the other stud in the picture looks to have seen better days too. time to break out the Aerokroil and 12 or 13mm 1/4" drive sockets. take your time and try not to force the remaining fasteners. good luck.

k

Thanks for the feedback. you're right, in the picture the other stud looks bad or at least stripped. I just crawled under there and it actually looks good. Threads are fine. Are you seeing anything else that I may have missed?

T

i see the carbon at the exh port but no burn/hot jet marks. make sure the old copper gasket is out before you put things back together.

k

The VW shops sell "step studs". They are normal 8mm on one end and 9mm on the other. A 9mm tap will just thread into the stripped out hole left by the missing stud, so you tap the 9mm threads and just screw the step stud in.
Really simple solution.

I really like that idea. I'll take a look.

Thanks!

T

So, when it was all said and done I bought a 9/8 step stud (some think that is the original size but who knows) and drilled and tapped the hole. The 9/8 stud went in fairly easily. Bolted it all up and ran it. There is still an exhaust leak so I need to figure out where it is coming from. Seems that i can feel it puffing under the HE connections so I guess the HE are not seated. I'll look into that tomorrow.

T

forgot the required pic.

So I put the car back up on stands this morning and went through them to ensure the HE were snug. Oddly enough the #3 was fairly loose. All were snugged up and I ran the car again. It was better but I am not sure if it was perfect.

Do the copper gaskets between the head and HE take time to seat? Is there something I am missing?

Let me know.

Thanks

T

Trevor there is a good chance that the ex. sealing surface in the head is no longer flat. I remachine that surface on every T4 head I do and I would say that well over 50% are no longer flat. The fact that you lost a stud and the HE was still torqued on one side makes it likely that the HE dug into the torqued side. You would think that the copper gasket would take the abuse, but the reality is that it passes it to the head. There really isn't much you can do about it without major work. Another bit of advise, if you can live with the leak that you have (if it isn't to bad) don't fool with the connection any more than you have to. Those old studs are brittle, I don't care how good they look! They will break if you overtorque them, and overtorque for an old heat fatiqued stud is well below the book torque spec.

In my experience ex. studs problems are quite often an indicator of aging heads that are ready for a complete overhaul. I have had MANY heads come to me for ex. stud problems and when I tore them down to do the work I found more serious problems that could very easliy have lead to catastrophic failure.
BTW you did a good job with the stud replacement. I know it's tough on the car. The stud closest to the rocker chamber (as your's was) is tight and hard to access. You would be amazed at some of the DIY repair job nightmares I've seen over the years!

Same thing happened on my '76. I put in the 9mm/8mm stud, and about 1000 miles later it was gone. Pulled out. If you pull an 8mm stud, you leave an 8mm hole, best case. It's actually worse than that because the hole is ragged. Anyway, when you tap to 9mm, you don't have full depth threads and it can (or almost certainly will!) pull out again

So, either go with a 10mm/8mm step stud, or a timecert with a 9mm/8mm stud. There are pros and cons of timecert vs helicoil, but I think the concensus is timecert in this application. It's harder to find and more expensive than helicoil, though.

My favorite metric fastener place is Bel-Metric- www.belmetric.com . They have the timecert kit AND the 10mm/8mm stud AND 9mm/8mm studs, as well as copper plated locking nuts.

There's an article I think at Ratwell.com on how to ensure the exhaust HE sealing surfaces are flat, and another on on how to anneal (soften) the copper gaskets so they'll seal more reliably...

Finally, install the heat exchanger, and then carefully check the alignment with the hanger in back. If you have to bend the HE to align the screw holes, you'll be leaving residual stress in the system at the mounting studs. I had to remove the hanger and drag the mounting holes (where it mounts to the transmission studs) to get a perfect alignment and not stress the head studs.

Piece of cake. Really, not bad. The aluminum head cuts threads for the timesert like butter, and the install was probably about 15 minutes (car was already up and HE off).

Good luck!
Jim

Jim

Posting here as well Trevor ...

My recent (and first) experience with the T-4 exhaust system:

One stud unscrewed from the head when I unscrewed the nut. I proceeded to remove the remaining nuts with no problems. I removed the exhaust system, cut the H/E tin off (cause I'm running an electric heater in the passenger compartment), wire brushed the whole thing and painted it w/ VHT.

Back to the head ... the one stud that came out was worn and had a helicoil in the hole. I screwed a NEW stud in and made sure it fully seated (using 2 exhaust standard nuts (locked together) ... then unlocked and removed both nuts.

Also, I had to pry the old head seals out. They appear to flatten and expand when torqued into place.

New head seals:

After I got the old seals out, I cleaned the recesses with a small flat-blade screwdriver. The seals need to seat well it into these recesses, as the nuts only torque down to 23 ft lbs. Most of them stayed in place OK, but a couple wanted to fall back down when I started fitting the system back up. It took me a few times to get it right. I balanced the exhaust system on my chest and lifted the back with my legs to fit it back up.

It was a real exercise for me ... I had a washboard stomach when I was done ... even though its still covered with a layer of fat

Great advice guys, thank you. I've put it up on stands for a third time. Removed all the heating connections and went thourgh all the nuts again. They are as tight as I dare get them and the car runs well now, not perfect, but pretty close.



Thanks, it wasn't easy...slow is good while working in there.


I suspect this is the problem.


Sorry to hear that, hope I don't follow suit.

Thanks again guys.

T