How to bi-pass low-n-high? '86 MGM Tudor

[Toploader]

Ok gents truth or consequences time:-(
I now doubt it is a ground issue!!.........I found that the speed of the blower appeared to slow down when I played with the amount of pressure I applied to the gas pedel......steady cruise nice steady cold air coming out of the dash registers........hit the gas to pass, and the air almost stops coming out of the vents..........and..........when the air does come back, for like two seconds heat comes out of the registers, then immediately changes over to ice cold air!........and as long as a steady speed is maintained no problem........stomp the gas, the air appears to stop coming out of the dash vents. The coffee can does hold Vacuum, so that is not the problem. In the hi-low position seems to help the situation.

[sly]

totally sounds like a vacuum issue with that stupid check valve at the firewall. Motorcraft YG337
Or the soup can has a hole in it or the hose to it does.

[Toploader]

What is the size of the "hose" that feeds the coffee can?.......the line on there now looks and feels like it is made of plastic?

[sly]

it should be. As long as it's not cracked and/or leaking, it should be good. Just something to verify. The end on the can should be rubber though. I would pressure test the can though. It should hold vacuum. I have a hand pump to do that with so it's easy for me to do that. Not sure if you've got access to one though. I also use that to test check valves. They should hold vacuum and leak no more than 1 PSI per minute. (at least that's the spec Ford uses IIRC)

[gadget73]

Make sure the can holds vacuum, and make sure the hose goes end to end. Seal off the thermal blower lockout if its not done already. That thing tends to leak like a sumbitch. Check the check valve too, they are also a problem area. Mostly the stuff in the car holds up OK, just the stuff under the hood fails.

[Toploader]

What size is it, I will run a new hose regardless. Also we tested the vac can with the hand pump, it held vac for at least 30 minutes.

it should be. As long as it's not cracked and/or leaking, it should be good. Just something to verify. The end on the can should be rubber though. I would pressure test the can though. It should hold vacuum. I have a hand pump to do that with so it's easy for me to do that. Not sure if you've got access to one though. I also use that to test check valves. They should hold vacuum and leak no more than 1 PSI per minute. (at least that's the spec Ford uses IIRC)

[Toploader]

Gadget, last year I removed the TBLS from the heater hose and plugged the ends with some screws. Also, I put in a new check valve YG-337

Make sure the can holds vacuum, and make sure the hose goes end to end. Seal off the thermal blower lockout if its not done already. That thing tends to leak like a sumbitch. Check the check valve too, they are also a problem area. Mostly the stuff in the car holds up OK, just the stuff under the hood fails.

[Toploader]

Gadget since the OEM vac can is long NLA, can I use a can from F-150 between '97-08?? It looks different made of plastic and looks like a flat pancake LOL

Make sure the can holds vacuum, and make sure the hose goes end to end. Seal off the thermal blower lockout if its not done already. That thing tends to leak like a sumbitch. Check the check valve too, they are also a problem area. Mostly the stuff in the car holds up OK, just the stuff under the hood fails.

[sly]

I've had the check valves die inside of 3 months... so it's worth checking it.

as for the vac can, you can use whatever you want. The best option is the aero/whale vac box with the relays mounted on the back. Great for cleaning up the relays in the front corner with.

[gadget73]

I've got the later box, but yeah, its really not important what exactly you use. It just needs to hold vacuum. The volume isn't overly critical, but you want something with a bit of size to it.

[Toploader]

When you say you have the later box, what exactly is that?..............and can I use the vac box as I said from a F-150 Ford Truck, also fits Lincoln cars.

And as to the size of the hose that attaches, do you know what size that is?

[sly]

should be 1/8 vacuum hose. You can replace it, but if it's not kinked or leaking... that line almost never fails. It's not actually plastic. Not sure what it is, but I've jacked with mine a LOT and it's never become brittle like the other color lines on the emissions crap. I actually prefer that line to vacuum hose. I'd replace the ends if anything at all if they're getting dry and hard/cracked.

[lincolnlarry]

The check valve is easy to check by mouth. LOL Air blows through one side and not at all through the other. That's my fancy testing procedure.

[sxcpotatoes]

The check valve is easy to check by mouth. LOL Air blows through one side and not at all through the other. That's my fancy testing procedure.

Yeah, but do you know who all else's mouths have been on that check valve?!?! You don't wanna get herpes!

[lincolnlarry]

Space herpes???