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Discussion Starter #1
I've been diagnosing various problems that seem vacuum related with my 68 factory A/C system. Yesterday it acted really strange. The automatic trans kept slipping out of gear, forward or reverse. I could put it in neutral, rev it a bit, drop back into gear and it would usually catch. Then I also noticed the power brakes were super sensitive. I only had it running for a minute while I moved it from one garage bay to another. Sound like a vacuum issue? A few days earlier I noticed a back leak from the A/C reservoir canister (i.e it wouldn't hold it's vacuum when the engine is revved or after it is shut off) so I installed an inline check valve in the hose supplying vacuum to the canister. That seemed to fix the back leak. Could it be a culprit?
 

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Your trans issue sounds like it's low on fluid. The vacuum modulator has no effect on shifting in or out of a gear, it only affects part-throttle shift points.
 

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Discussion Starter #3
Your trans issue sounds like it's low on fluid. The vacuum modulator has no effect on shifting in or out of a gear, it only affects part-throttle shift points.
What is the proper way to check trans fluid level? The Shop Manual doesn't go into that, at least not in the auto trans section. I kinda remember to check some old trans you had to have it in drive gear at idle.
 

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What is the proper way to check trans fluid level? The Shop Manual doesn't go into that, at least not in the auto trans section. I kinda remember to check some old trans you had to have it in drive gear at idle.
Start the engine and let it run to operating temperature, park on level ground and with engine still running, pull the dipstick, wipe, replace and pull again to read.

It is likely you're low on fluid, look for a puddle when you move it, and when looking for a vacuum leak there is a short section of hose from the engine to the modulator line and even a tiny section of hose from the modulator line to the valve.
 

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Discussion Starter #5 (Edited)
Doh, Checked it like you said and nothing shows up on the stick! I also found I have an exhaust leak at the rear most port. I got my finger close enough to feel the hot exhaust pulsating out from there. I guess I have more work to do on this old thing.

Forgot to ask: is there a modern equivalent to the type ATF listed in the old Shop Manual? Seems like I can never find the type listed for these old cars.
 

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C4s are kinda leak-prone, especially if they sit too much.
I would STAY AWAY from stop-leaks.

The exhaust leak may be "cured" with getting the bolts to the right torque, but don't overdo it, you may hafta RnR it. Be sure you aren't feeling exhaust coming from a heat riser tube port that has no tube in it.

Type F is still available, I have gotten it at Wallet-Mart, AutoZane, O'Really's, Adverse Auto (haha) and is what yours was designed to use. You can use the Mercon Dexron type in a new build but I wouldn't mix the two for a top-off.
 

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Doh, Checked it like you said and nothing shows up on the stick! I also found I have an exhaust leak at the rear most port. I got my finger close enough to feel the hot exhaust pulsating out from there. I guess I have more work to do on this old thing.

Forgot to ask: is there a modern equivalent to the type ATF listed in the old Shop Manual? Seems like I can never find the type listed for these old cars.

Use Type F. You can get it at pretty much any decent parts store. Even the Ford dealers carry it again.
 

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Discussion Starter #8
C4s are kinda leak-prone, especially if they sit too much.
I would STAY AWAY from stop-leaks.

The exhaust leak may be "cured" with getting the bolts to the right torque, but don't overdo it, you may hafta RnR it. Be sure you aren't feeling exhaust coming from a heat riser tube port that has no tube in it.

Type F is still available, I have gotten it at Wallet-Mart, AutoZane, O'Really's, Adverse Auto (haha) and is what yours was designed to use. You can use the Mercon Dexron type in a new build but I wouldn't mix the two for a top-off.
here's where I feel the exhaust leak. Looks like the gasket has burned through. Looking at this again I remember what a bear that A/C compressor was and it appears it has to be moved to get at the front bolts. I might put this one off for a bit.
 

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Also, after adding ATF, cycle through all the gears to fill the hydraulic circuits and get an accurate reading. Check level in neutral.
 

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Discussion Starter #10
Put a quart and a half of type F in it. Seems to have fixed that problem. I got it a little over the full mark. So far I haven't seem any foaming. Do I need to worry about that?

Now back to that exhaust manifold gasket. It definitely needs replaced. I'm having a problem getting a socket on any of the bolts. I'm sure they are 1/2 inch but I can't get either 6 point or 12 point on any of them. I've wire brushed one and used PB Blaster with no luck yet. I tried a 14 mm on one but it started to round off the edges and of course 13 mm won't go on either. Any tips?
 

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Put a quart and a half of type F in it. Seems to have fixed that problem. I got it a little over the full mark. So far I haven't seem any foaming. Do I need to worry about that?

Now back to that exhaust manifold gasket. It definitely needs replaced. I'm having a problem getting a socket on any of the bolts. I'm sure they are 1/2 inch but I can't get either 6 point or 12 point on any of them. I've wire brushed one and used PB Blaster with no luck yet. I tried a 14 mm on one but it started to round off the edges and of course 13 mm won't go on either. Any tips?
The bolt heads are probably rusted to the point that they are "in between" sizes. IIRC, all the Ford exhaust manifold bolts are 3/8-16 and should have a 9/16" head. 14mm is only .012" smaller than 9/16. It might grab it if you use a good 6 point socket.

Be very careful when removing the bolts. Crack it loose, then tighten again, loosen 1/8 turn, tighten. You want to go maybe 1/8 turn more at a time. Keep hosing it with Blaster until it starts to come out easily. If you feel resistance, stop, spray it, and turn it back in a couple turns.
 

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Discussion Starter #12
I just ordered a 17/32 socket from Home Depot. It's 12 point and for a 3/8 drive so it might not work. I did see a 1/2 drive 6 point 17/32 on Amazon which I might have to try if the 3/8 drive doesn't work.
 

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Take Hemikillers advice..all of it!
Especially..the use a 6 point socket. TOO easy to round a rusted bolt with 12pt..
Good luck.. and take your time..allow the penetrant time to work.. you won't want to spend your time removing broken manifold bolts from your engine.

Sent from my SM-G950F using Tapatalk
 

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Discussion Starter #14
Looks like there are 2 brands of exhaust manifold gaskets available, Fel-Pro and Mahle. Is either better? It's interesting that Fel-Pro costs more at O'Reilly's but half the cost of Mahle at Rock Auto.
 

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Keep in mind that sometimes the easiest way to gain access to a nut or bolt is from a different vantage point. For example, on a big block motor some of the lower exhaust manifold bolts are best reached from below the car using extensions, and universal joints to get around obstacles. Also start several days early with PB Blaster (penetrating oil) on all the nuts and bolts reapplying it several times. Rusted nuts and bolts are prone to breaking off if forced. Too much force can lead to broken bolt extractions and they are usually time consuming and a PITA. Be patient. If nothing works, look into heat (a torch) to take advantage of expansion and contraction of the rusted metal. Lastly, once the exhaust manifold is off the engine, have it checked for warpage of the mating surface. A machine shop can true up that surface by re-surfacing the mating surface if needed.
 

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Here is a nice little test on penetrating oils


I am pretty embarrassed to have purchased a $19 can on Kroil. :(
 

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Discussion Starter #17
I wonder if my problem has to do with locking tabs on the exhaust manifold bolts. The Shop Manual says to bend them back before removing the bolts. I can't tell if I have them on there or not. Of they are, then they are all under where I can't see them. I think maybe I can feel one on the one bolt I've been trying to loosen but I can't get a very small screw driver to catch it to bend it back.

I got a 17/32 3/8 drive 12 point and tried it this morning. It fit on pretty well but rounded it off when I gave it some torque. I guess I should have waited to find a 6 point. I'm about to give this up or find someone who will take it on. Anyone know of a shop that would attempt it in the St. Louis area?
 

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I'm not sure if Ford used a gasket there, originally, or not. After removal, give it a good hard look over.

FWIW, when faced with the possibility of snapping a bolt off in the head (with my luck, usually either flush or worse), I've resorted to lopping the heads off the bolts, removing the manifold, then using heat and my stud remover to get the remainder of the bolt(s) out in one piece.

 

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Discussion Starter #19
I'm starting to look at new manifolds if need be. I see Summit has one for 200 CID 6 cyl but the years of application listed are for 1964-67. Is the 68 manifold different?
 

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Discussion Starter #20
Here is a pic of a 6 cyl bolt set. I don't see any locking tabs like for a V8 in the 2nd pic. Can I assume a 6 cyl didn't have them?

Also if I apply heat, using a propane torch like I use for sweating copper pipe, where would I direct the flame? Onto the manifold or where the manifold meets the head?
 

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