General Motors had this great idea to make their intake manifolds out of plastic to save weight and thus save fuel. But was it such a good idea?
I guess I should start off by saying I was never a fan of General Motors or the vehicles they build. After 40 years of fixing them, talking to factory reps and engineers I am more than familiar with their quality, or lack thereof. It's a well-known fact that General Motors is the worlds leader in motor vehicle recalls. 2005 was a record year for GM recalls with a recall on almost every make and model it builds for at least one problem and as many as 9 different problems on some vehicles. In the last four months there were 21 mandatory and voluntarily recalls on GM vehicles.
When GM was asked to comment on this they were rather proud in saying that they had greatly improved their vehicle inspection procedures. All this means is they aren’t making better cars, just getting better at finding defects that previously went undetected.
Now the problem is the intake manifolds and gaskets. They started making their intake manifolds out of a plastic material in order to save engine weight and thus save precious fuel. The problem is that the plastic cannot withstand the heat in that part of the engine and as a consequence the material fails, often with catastrophic results. For example, the owner of a 1998 Pontiac Bonneville where "the manifold shattered and caused an engine fire. Our mechanic showed us the melted gas line and told us he was seconds from the gas tank blowing up."
I personally have seen 14 broken plastic intake manifolds in the last year. That's aside from the number of intake manifold gaskets replaced. These are not high mileage vehicles either. I have seen intake manifolds and gaskets go bad with as little as 31,000 miles on the vehicle.
GM recognizes this is a problem but they are doing noting to help the people who own these vehicles. On May 26, 2004 GM released a Technical Bulletin (TSB) 04-06-01-017 regarding “New Upper Intake Manifold and Gasket Kits”. In it, it says, “In addition some of the gaskets have been updated to a more robust design”. Only “some of the gaskets”, why not “all”?
Then on January 18, 2006 GM issued another TSB concerning this problem. In it, it says,
Condition:
Some owners may comment on excessive engine coolant consumption, or an engine coolant leak near or under the throttle body area of the upper intake manifold.
Cause:
Upper intake manifold composite material may degrade around the EGR stove pipe and could result in an internal or external coolant leak.
Then it goes on to detail the repair procedure.
Now a TSB is not a recall in any way, nor is it a free repair for the owners. A TBS is for known problems and the procedures to repair that problem.
The cost of intake manifold and gasket related repairs can range from $800.00 of a simple intake manifold gasket replacement all the way to, over. $3,500.00 for a complete engine replacement.
General Motors is not inclined to recall these vehicles or even help their customers with the cost of repairs simply because of the vast scope of the problem. It involves millions of V-6 engines from 1995 to the present. The cost to GM to fix this problem would run into the billions. Something financially strapped General Motors simply cannot afford. A class action lawsuit has been filed against General Motors on behalf of GM vehicle owners to recover the cost of repairs to their vehicles.
This lawsuit is ongoing but since I have been hired as an expert I will not be able to report an any details.
The copyright of the article GM Plastic Intake Manifolds in Auto Tech & Repair is owned by Vincent Ciulla. Permission to republish GM Plastic Intake Manifolds in print or online must be granted by the author in writing.
