MAP sensor vacuum hose

[clickittyclank]

1987 GMC Sierra Classic, 350 tbi

Was having some issues and got a code 45 so started looking at some culprits and found one end on the MAP sensor vacuum hose had some cracks in the boot. Plugged one end with a finger and blew into the other and was getting some leakage.

The nipple on the MAP sensor is straight up into the air cleaner and the other is at the rear of the TBI. What have yall been using to replace these old brittle lines? Finding boots and whatnot at this size has been difficult so far.

Basic measurement with a tape - 3/16” ID, 1/4” OD, roughly.

I know this is a pretty basic question but any suggestions or ideas would be appreciated.

 

[DoubleDingo]

Can a straight piece of vacuum hose of appropriate diameter and length be used, or does it need the 90 degree bends?

There might be replacement vacuum hoses available like the one in the photo as well.

 

[clickittyclank]

Connecting to the back side of the tbi would be fine straight but connecting to the MAP sensor itself looks like it would need an elbow of some sort. With the air filter on there isn’t much room over there.

Seen some similar parts for newer models but hose/boot specs aren’t listed. Will give them a call tomorrow and see if they have the info.

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[jcperformance]

1987 GMC Sierra Classic, 350 tbi

Was having some issues and got a code 45 so started looking at some culprits and found one end on the MAP sensor vacuum hose had some cracks in the boot. Plugged one end with a finger and blew into the other and was getting some leakage.

The nipple on the MAP sensor is straight up into the air cleaner and the other is at the rear of the TBI. What have yall been using to replace these old brittle lines? Finding boots and whatnot at this size has been difficult so far.

Basic measurement with a tape - 3/16” ID, 1/4” OD, roughly.

I know this is a pretty basic question but any suggestions or ideas would be appreciated.

Replacing those brittle MAP vacuum lines on a TBI setup can be a pain since the specific molded boots are hard to find. Most people swap them out for high-quality silicone or rubber vacuum tubing in 5/32" or 3/16" ID, which stretches over the TBI and MAP nipples for a tight seal without the OEM boots. If you want to keep the hard plastic look, you can use heat-shrink tubing over the ends or check the "Help!" section at a local parts store for universal vacuum connectors that match your 3/16" measurement.

 

[clickittyclank]

Thanks for the responses. I’m all for replacing them with silicone tubing. My main issue is that MAP sensor nipple they points directly up into the air cleaner. Using straight tubing on that one will surely kink.

Think I can temporarily take a boot from the evap canister for the MAP sensor but would like to find a permanent solution to that one hose. Evap canister will be replaced with new hose.

 

[clickittyclank]

Although the original inner diameters of the hoses on the truck were 5/32 and 3/16 it looks like I would need 1/4” tubing if I switch to silicone.

 

[jhe4500]

Although the original inner diameters of the hoses on the truck were 5/32 and 3/16 it looks like I would need 1/4” tubing if I switch to silicone.

I just replaced the same thing on my truck over the weekend. 5/32 silicone worked well, and no kinking issues, but I'm running an Edelbrock air cleaner with a 1" spacer ring on top of the metal factory ring

 

[KWMECH]

MAP sensor signal is important to a TBI system. 1/4'' hose and not excessively long. Can substitute with just a rubber line

 

[Ricko1966]

Connecting to the back side of the tbi would be fine straight but connecting to the MAP sensor itself looks like it would need an elbow of some sort. With the air filter on there isn’t much room over there.

Seen some similar parts for newer models but hose/boot specs aren’t listed. Will give them a call tomorrow and see if they have the info.

Site Maintenance

Use a hard plastic 90 and a 1 inch piece of vacuum line to connect at map. Other end of 90* use vacuum line to TBI you can use a second hard 90 at Tbi if necessary. Can you just put a loop in a piece of regular vacuum tubing,instead of trying to make a straight shot.

 

[clickittyclank]

Thank you all for the suggestions. I had a 1/4" line on there but wasn't 100% happy with it and this is what I've settled on for the time being. Basically what y'all described - boot, hard line, 5/32" silicone tubing. Still not 100% happy with it as that boot thats on there is one of the originals but it should hold for now. Blew through each end with the other plugged and didn't feel/hear any leaks. Also swapped out quite a few of the other vacuum lines while I was in there. Only one that remains is the EGR to TBI line as the EGR end is 5/32 and the TBI side is more like 3/16.

 

[DoubleDingo]

Thank you all for the suggestions. I had a 1/4" line on there but wasn't 100% happy with it and this is what I've settled on for the time being. Basically what y'all described - boot, hard line, 5/32" silicone tubing. Still not 100% happy with it as that boot thats on there is one of the originals but it should hold for now. Blew through each end with the other plugged and didn't feel/hear any leaks. Also swapped out quite a few of the other vacuum lines while I was in there. Only one that remains is the EGR to TBI line as the EGR end is 5/32 and the TBI side is more like 3/16.

I have done fixes like that on my 91 Cherokee, but without the zip tie. I use a long piece as a sleeve to fit over the failed hose, and it does not leak. I have two like this, one I purposely cut to do this fix on, and the other was an oops where I used a wrench instead of a screwdriver to undo the air cleaner housing snaps, and the wrench slipped and snapped the vacuum line. They did eventually waller out and not hold a tight seal, but I also used hose I had handy at the time. Last Fall I got hose that was a snug fit, should be good for another 20 years, as that's how long the wrench oops lasted, the other was a shorter time period but with wrong diameter hose. With the snug fit it shouldn't ever leak again.

 

[clickittyclank]

That gives me hope it will hold up just fine. Nice to have some folks to discuss these things with. There are definitely some issues that take a little creativity.