Hunting down Motronic vacume leaks: What does the thermo-switch do?

[amatow]

I am going through the vacume lines on my 87 fuel injection. I see many paths for potential leaks.

I was surprized to see the "thermo-switch" screwed into my throttle body.

I found the name using the pelican parts list ( very helpful).



I also see what appears to be a vacume line going into a valve near the oil tank. Any idea what that does.

[ChrisBennet]

I'd be surprised too. There isn't supposed to be a thermo-switch screwed into the throttle body.
-Chris

[jeff m]

Sorry edited posted in wrong place.

[amatow]

Chris,

If you check out the parts catalog on line under motronic, throttle body, thermo switch.

anyway, I will clean up any vacume leaks and go on.


Anyone have a description of the vacume lines / vacume circuits in a motronic 3.2?

[ChrisBennet]

Originally posted by amatow
Chris,

If you check out the parts catalog on line under motronic, throttle body, thermo switch.

anyway, I will clean up any vacume leaks and go on.


Anyone have a description of the vacume lines / vacume circuits in a motronic 3.2?

Well I'll be! You're right! I didn't even know that was a valve.
I stand corrected.

I guess I should try to be helpful after all the grief I've given you.
Here are some places to check for intake leaks:
1. The flexible portion of the 3/8" rigid vacuum pipe that comes out of the back of the rubber throttle body elbow. They tend to crack. Mine is fixed with some hose and hose clamps.
2. The "rubber sleeve" right next to the oil filler cap. It is a rubber hose about 2-3" long that necks down.
3. There are 3 vacuum outlets on the back of the throttle body/thermo valve. 2 come off the thermo valve, one comes of the throttle body itself. A hose connects one of the thermo valve outlets right back to an outlet on the back of the throttle body. The other thermo valve outlet goes to a rubber "Y" connector. From the "Y" connector, 2 plastic lines go to the fuel damper and pressure regulators at the ends of the fuel rails.
-Chris
P.S. I have pics of #1, #2 I can post when I get home.

[ChrisBennet]

Here are some pictures of the possible leak culprits:

This on a 1989 motor (See #1 above):


This on a 1986 motor (See #1 above):


This is the one near the oil filler cap (See #2 above):

-Chris

[ben parrish]

Chris
Where does the third hose go?
I have an 86 with a vacume line unattached that I can't figure out. I feel the one that is routed back to the throttle body and the one that goes to a y . The line in question is routed to the passenger side of the engine..I can't figure it out?
Any help would be appreciated

[ChrisBennet]

Originally posted by ben parrish
Chris
Where does the third hose go?
I have an 86 with a vacume line unattached that I can't figure out. I feel the one that is routed back to the throttle body and the one that goes to a y . The line in question is routed to the passenger side of the engine..I can't figure it out?
Any help would be appreciated

Ben,
Feel along the left fuel rail (1/2" square "pipe" that goes along the tops of the injectors) until you get to the back of the engine compartment on the left side. You should find a cylindrical (~2x2") fuel pressure regulator with some fuel hoses going into it and a little rubber "pony tail" on the top. The skinny plastic line that goes from the "Y" on the back of the throttle body goes into the "pony tail".
-Chris

[ben parrish]

Chris, I am talking about another line. All the lines are small in diameter. Got the one that goes back to the throttle body..Got the one that attaches to the "Y" and the lines that leave this junction.. There is a third line; a small line attached to the throttle body, approx 2.5 to 3' in length that was going to the passenger side of the engine.

[ChrisBennet]

Ben,
Do you have cruise control? I think a small (1/4", 3mm ID) hose goes to the vacuum servo on the cruise control on some models. They changed to another servo at some point. My '86 has the vacuum type, I don't know what the '87 has.
A larger (9-10mm ID) hose comes off the same CC servo and goes nowhere on my car and a friends '86.
I don't have my car here so this is from memory.
-Chris

[amatow]

Chris thanks for the pics.

The hoses by the oil filler were loose. I am wondering if anyone has a vacume diagram.

What does the hose by the filler do? It seems to have a PCV type check valve. It seems also to be controlled by a vacume switch under the hinge. Very strange. My Bently manual calls it an emmisions line.

On you second picture what is that stuff? It seems to be connnected to the brake booster up front but why all the complecated stuff?

Anyway, I found several places leaking small amounts. I have not yet put on the throttle body and confirmed that it helps any.

[ChrisBennet]

Originally posted by amatow
Chris thanks for the pics.

The hoses by the oil filler were loose. I am wondering if anyone has a vacume diagram.

What does the hose by the filler do? It seems to have a PCV type check valve. It seems also to be controlled by a vacume switch under the hinge. Very strange. My Bently manual calls it an emmisions line.

On you second picture what is that stuff? It seems to be connnected to the brake booster up front but why all the complecated stuff?

Anyway, I found several places leaking small amounts. I have not yet put on the throttle body and confirmed that it helps any.

The 1st and 2nd pictures show the same vacuum line but it is shaped differently for different years. The part that leaks has new hose clamps on it.
-Chris

[peter911]

Guys,
I've been reading your thread on the Vacuum lines: nice to see others are baffled by the "Plumbing" around the 3.2???
Has any one found what the small (1/4") rubber hose from the Y piece (LH side, under heater fan), that goes forward, through the firewall does?
Is it the same hose which appears in the front boot, LH side (your drivers side), and which changes to a hard plastic pipe (1/8")(I think)?
Does this pick-up the vapours from the fuel expansion/charcoal tank (inside the LH wing- behind the headlight bucket)??
When I try and blow through this hose (from back to front) it seems blocked? Unless of course these are 2 different hoses?
At present, the fuel expansion tank vents to no where.
My cruise control servo is also Ka-put; the cable is broken next to the throttle linkage joint. Has any one any experience on rebuilding this servo? Just the cable alone is worth 150 pounds; servo is worth 250 pounds!!!!!!!
Come back?
Peter