Vacuum lines L36

Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's, Olds 98 91-96, Buick Lesabres and Park Avenue 91-96. Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.
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Yurka
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Year and Trim: 1997 Pontiac Bonneville SE

Vacuum lines L36

Post by Yurka »

Hi. I'm installing an engine on my Bonneville after repair. I have a question. How are vacuum lines connected to the trans through twin metal tubes ?
Please take a picture of an engine without a top cover from the throttle body side.
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95naSTA
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Re: Vacuum lines L36

Post by 95naSTA »

If it's your 98, there shouldn't be a vac line that goes to the trans. 97 was the last year for the vacuum modulated 4t60-e, your 98 should have a 4t65-e with electronic line pressure modulation.
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95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.
Yurka
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Year and Trim: 1997 Pontiac Bonneville SE

Re: Vacuum lines L36

Post by Yurka »

Sorry, my mistake in indicating the car. That's right, 97.
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harofreak00
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Re: Vacuum lines L36

Post by harofreak00 »

Also, it should only be a single vacuum line going to the trans modulator.

Maybe you should post a picture of what you're working with and we can help you that way.

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95naSTA
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Re: Vacuum lines L36

Post by 95naSTA »

For the dual line, one goes to the charcoal canister and one goes to the vacuum modulator on the front of the transmission.

Here's a pic from over 20 years ago of a cold air intake I made for my 95, also L36/4t60-e equipped. You can see the line going down to the transmission vacuum modulator then there's a line going forward from that area which goes to the charcoal canister.

Image
Image
95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.
Yurka
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Joined: Thu Sep 11, 2025 3:43 am
Year and Trim: 1997 Pontiac Bonneville SE

Re: Vacuum lines L36

Post by Yurka »

I see from the diagram that one line goes to the charcoal canister past the service port, and the other to the transmission.
The bend in the tubes does not allow for normal direct connections. Maybe I oriented them incorrectly.

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95naSTA
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Re: Vacuum lines L36

Post by 95naSTA »

At first look, it seems like the double tube is upside down but it's hard to tell without being there.

I found this pic that might help:
Image
Image
95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.
Yurka
LE Member
Posts: 4
Joined: Thu Sep 11, 2025 3:43 am
Year and Trim: 1997 Pontiac Bonneville SE

Re: Vacuum lines L36

Post by Yurka »

[quote="95naSTA"]At first look, it seems like the double tube is upside down but it's hard to tell without being there.

I found this pic that might help:

Thank you for your help.
The tube seems to be installed correctly, but the upper edge to the EVAP is bent strangely. I will connect it with rubber hoses.
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