What happens when your intake manifold cracks?

Written by edmund gary
  • Share
  • Tweet
  • Share
  • Pin
  • Email
What happens when your intake manifold cracks?
Plastic intake manifolds do not last through the car's life. (intake hose image by Five Arrows from Fotolia.com)

General Motors and Ford Motor Company embarked on a "more environmentally friendly" manufacturing process in the early to mid 1990s. Buick sales brochures from that period state that plastic parts were made of recyclable materials. The most controversial of these plastic parts is the intake manifold cover.

Cracking Manifolds

According to Southtown auto writer Ira Siegal, plastic intake manifolds would crack because the seals were compromised. Engine parts would expand and contract. The plastic intake manifolds do not have the tolerance for such conditions. Robert Lane of Blue Oval News stated that the intake manifolds would crack and cause an internal coolant leak. Plastic intake manifolds with water passages built into them are prone to cracking, according to Intake Manifold Help.

Affected Vehicles

Plastic manifold problems affected Fords equipped with the 4.6 litre V8 engines that were built between 1996 and 2001. The models in question are Lincoln Town Car, Mercury Grand Marquis and Cougar, Ford Crown Victoria, Thunderbird and Mustang.

General Motors plastic manifold problems occurred in the 3.1 and 3.4 litre V6 engines from 1992 to 2004. Cracks were discovered around the exhaust gas recirculation (EGR) stove pipe and coolant contaminated the oil by leaking into the crankcase. Major engine failure would result if the condition was not caught in time. Cadillac was unaffected by the intake manifold problem.

Plastic Manifolds and V-Type Engines

Plastic intake manifolds and V-type engines were not a good match according to Intake Manifold Help. The intake manifold has to bridge between two cylinder banks. The angles may not be at the exact specifications, and bolting the plastic manifold in place could cause distortion. Secondly, V-type engines generate more heat than an in-line four-cylinder engine. Third, coolant from both cylinder heads is routed to the front area of the intake manifold to a single thermostat.


General Motors settled a class-action lawsuit from disgruntled owners of GM vehicles in 2009. The suit alleges that GM's long-life coolant was the cause of the plastic manifold failures, which affected their cars. The terms of the settlement state a graduated disbursement plan based on the number of years the customer owned the vehicle before the manifold repair.

Ford issued seven-year warranties to its fleet buyers through the Owner Notification Program in 1999. Law enforcement agencies, taxicab companies and limousine companies were able to take advantage of the offer, but the civilian owners were not included in the plan. A similar program was offered to the civilians after Ford lost an appeal to keep 100,000 people from suing the company over the faulty intake manifold. The suit sought more than £65 million in damages.

The Promise of Plastic Intake Manifold

Plastic intake manifolds held the promise of improving manufacturing efficiency. The modular assembly would enhance environment performance by reducing waste. Cost reductions were realised by Ford and General Motors during the manufacturing process, according to Intake Manifold Help. The plastic intake manifold was used in effort to replace the metal structure "behind the grill," according to Susanne Mueller of BASF's Performance Polymers business unit of North America.

Don't Miss

  • All types
  • Articles
  • Slideshows
  • Videos
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the eHow.co.uk site, you consent to the use of cookies. For more information, please see our Cookie policy.