M74-1020-001 - Genuine Paccar Exhaust Bellows Flex Pipe - 1 - wisentpartscenter.com

Description

Paccar M66-7671-302 Exhaust Bellows Flex Pipe - Genuine Paccar Insulated Exhaust Bellows for Peterbilt and Kenworth

The Paccar M66-7671-302 is a genuine insulated exhaust bellows, also called a flex pipe. It is the braided stainless flex section in the exhaust that absorbs engine movement and vibration so it does not crack the rest of the exhaust and aftertreatment.

Key Functions:

- Absorbs engine movement and vibration in the exhaust
- Braided stainless flex with heat insulation
- Includes V-band clamps

Fitment & Specifications:

- Peterbilt and Kenworth with MX-13
- Insulated exhaust bellows, V-band ends
- Includes clamps

Verify fitment with us before ordering to ensure the correct part for your application.

Purpose of the Part

The engine rocks on its mounts while the exhaust and aftertreatment are held more rigid, and something has to take up that movement or the pipes and DPF housing would crack. The bellows is that flexible link. The inner liner keeps the exhaust flowing smooth while the outer braid contains it and handles the flex, and the insulation keeps the heat in the pipe.

Issue Symptoms / When to Replace

Exhaust leaking or ticking at the flex, a torn or blown out braid, soot streaks around the bellows, and rattling from a broken inner liner. A failed bellows leaks exhaust and lets movement carry into the aftertreatment, which can crack more expensive parts downstream.

Before replacing it, check the engine and exhaust mounts, since a broken mount lets the engine move more than the bellows can handle and will tear the new one too.

Brand Information

PACCAR is the parent of Peterbilt, Kenworth and DAF and builds this bellows to the length, diameter and flex the MX-13 exhaust needs. The insulation and heavy braid are part of that spec. A thinner aftermarket flex will bolt in but tends to blow out or crack sooner under the heat and constant movement, which is why the genuine part carries the 24 month warranty.

Installation Notes

Let the exhaust cool first. Check the engine and exhaust mounts before fitting the new bellows, excess movement from a bad mount is what tears these. Do not stretch or compress the bellows to make it fit, it has to sit at its natural length. Use the new V-band clamps, get the flex section lined up straight so it is not preloaded, and tighten the clamps evenly. Run it and check for leaks.

How to Identify an OEM Part

Genuine PACCAR bellows come in PACCAR Genuine Parts packaging with the part number, and the flex, end fittings and clamps are heavy gauge stainless. Check the number matches your order and compare the length and end style to the pipe coming off.

Why buy from Wisent Parts
  • ⏱️
    Fast shipping
    Orders before 12PM EST ship same business day.
  • 🛡️
    180-day warranty
    All parts covered from delivery date.
  • ↩️
    Easy returns
    30-day returns.
  • ✅
    Verify fitment
    Send VIN/ESN and we’ll confirm.

Shop with confidence

Warranty & Return Information
Warranty Information

Wisent Parts offers a 180-day warranty on all parts from the date of delivery. This warranty covers orders placed directly through our website. If a part fails during this period, we’re here to help - whether it’s a replacement, repair, or refund. For full details, refer to the Warranty page.

Return Information

Wisent Parts accepts returns within 30 days of delivery. All returns are subject to a restocking fee. To qualify, parts must be unused and in their original condition. For full return instructions and restocking fee details, please refer to the Returns page.