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1971 Mark III Questions & Follow Up

Bill,

I'm writing again about my Mark III with 91,000 miles. I recently came across one of your letters that discussed replacing a heater core, and you mentioned needing to remove an emissions tube that's located on the rear of the engine. You included a helpful diagram, and I was confused that my engine didn't have what I saw on that diagram. I did find two metal tubes, one on each side of the rear of my engine that had been cut off about six inches from the engine and crimped at the end. I concluded that this tubing was probably connected to the thermactor air pump and check valve system that I couldn't locate on my car. The light bulb finally went on when I realized that the two empty mounting holes above the alternator are where the missing air pump must belong. I'm guessing that the original owner's mechanic removed that system because he either damaged it, or didn't want to work around it when they replaced the heater core at 90,000 miles.

I've read that removing this system is pretty common, and my engine runs fine, but a little loud. However the tube on the driver's side is rather loose and in worse condition than the passenger side tube. I've attached a pictures of both sides, and you can see a hole in the driver's side picture. The tube is delicate enough that the hole that grew larger when I touched it and the debris fell into the tube.

First question: Should I be concerned about the debris making its way into the engine? I haven't started it since the hole in the tube opened up.

Second, I'm not fond of the crimp method that was used to close these tubes. Can these tubes be completely removed and the holes filled with a bolts or freeze plugs? I can't find any details in the shop manual how to remove/install them?

Finally, should I try to replace the missing components if I could even find them? I do have a moderately loud exhaust noise that seems to come from the driver's side, and haven't identified it as a cracked exhaust manifold or pipe seal yet.

Thanks for your input and advice.


Bradley

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Bradley -

Special size frost plugs are available to seal these emission holes. There are two needed for each cylinder head. Another approach is to remove the rear crimped pipes and have them shortened to a stub and an improvised plug welded on to them. Any rotted or loose pipes or frost plugs will result in an exhaust leak. For further information on new press in plugs call our office and ask for Al. I have spoken to Al and he is aware that you may call.

Sincerely,

Bill

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Bill -

Thank you very much for the follow-up answer. I talked with Al, and he confirmed what I thought about finding plugs and the challenge I'll have installing them so close to the firewall. I've also since confirmed that the 6'" of pipe remaining on the driver's side is rotten and falling apart on the underside all the way down its length to the head, so there's no salvaging what's there. Getting a grip on that 5/8" bolt that secures the U-shaped clamp holding the pipe in the block is proving difficult with the engine in the vehicle, even with the hood off. Any suggestions how to get a good grip with a wrench without removing all the hydraulic pipes and other equipment in that area? I'm concerned about breaking the bolt because I can tell it is pretty tight.

Bradley

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Bradley -

Some of the other components will possibly need to be removed or repositioned temporarily in order to clear the way for an easier removal. Whenever I found it necessary to remove these pipes in the past I was able to configure a flexible ratchet with a good "six point socket" without too much trouble. Others here have used flexible wrenches that ratchet. No one has mentioned a broken bolt while removing these pipes. If you feel that you don't have the necessary tools etc. you may need to take the car to a shop that is capable. The only other alternative is to remove the heads or the heater plenum.

Sincerely,

Bill

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Bill,

You advice helped me feel more comfortable tackling the project, and I can report success. With the removal of the cruise control bellows and a swivel ratchet extension, I got that bolt out so I could remove the rotting pipe. I plugged the hole with an oil pan drain plug that I cut shorter, fashioned a washer with exhaust gasket material and then clamped it to the head with the existing fastener assembly. Now it runs nice and quiet.

Bradley

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Good work Bradley -

You got motivated, studied the problem and found a solution. A little creative improvisation on your part helped you solve the problem.

Sincerely,

Bill