Dealers repairing Chrysler V6 engines

Chrysler Group dealers are replacing malfunctioning cylinder heads on a small percentage of 3.6-liter Pentastar V6 engines.

And a recent shortage of replacement heads means some customers have been without their vehicles for weeks, some dealers say. Chrysler is paying for their rental cars. A cylinder head covers the engine block, enclosing the cylinders and forming the combustion chamber.

The engine powers most of Chrysler's best-selling vehicles, including the Jeep Grand Cherokee and Wrangler. By the end of the year, the 3.6-liter Pentastar will be Chrysler's only V6 engine in production, though a smaller-displacement version is scheduled to appear next year.

To fix the problem, which Chrysler executives declined to describe fully, the company designed a "more robust" head, which it started manufacturing about six weeks ago.

At the same time, Chrysler started using the redesigned heads on new Pentastars, the company said.

A source familiar with Chrysler's parts database said that in late July more than 1,300 vehicles nationwide were in dealership service areas awaiting replacement parts. He added that Chrysler's internal parts system said it was averaging more than 300 new requests a week for the replacement cylinder heads.

Doug Betts, Chrysler's senior vice president for quality, last week acknowledged the backlog. He said: "The biggest mistake we made is taking our eye off the ball on service parts. That always gets the dealers' attention. Our intention is to always satisfy the needs of the service market ahead of production. This came to my attention a couple weeks ago. We have parts in the pipeline to remedy that shortfall."

After Chrysler executives spoke with Automotive News, the source with access to the company's parts database said Chrysler "flooded" its system with new replacement parts last week, eliminating a bank of about 1,300 unfilled orders nationwide. He said the company now has nearly 3,000 available parts to fill dealer orders.

However, he said the average weekly demand had risen to more than 500 new requests.

Betts said the problem has been found in about half of 1 percent, or about 7,500 of the about 1.5 million Pentastar engines that were built over the past two years. Betts acknowledged, however, that more problem cylinder heads could surface.

Chrysler executives declined to describe fully the nature of the problem or identify exactly when it was brought to their attention. They said they have been investigating it "for months." In a dozen complaints filed with the federal government, some customers report a ticking sound from the engine, stalling and other problems. The check-engine light illuminates on all affected engines.

The executives said the problem arises only with an unusual combination of factors, such as low-quality fuel and unspecified driving conditions. Chrysler said the issue does not disable the engine.

The Pentastar engine has an unusual design. The engine's exhaust passages merge into a single outlet in the aluminum cylinder heads before exiting to the exhaust manifold. Most modern engine designs send hot exhaust gases in separate passages in the head to the exhaust manifold.

Bob Lee, Chrysler's chief of engineering, said, however, that excessive heat was not a factor in the malfunction and that his engineering teams spent months isolating its causes.

"This one was a challenge," Lee said. "The good news is that it's a very small percentage of the customers and it's something we've taken care of."

Betts, who as head of quality oversees a team of 1,200 people dedicated to improving Chrysler's once-woeful quality reputation, declined to identify the exact cause of the problem.

He said the malfunctions were the result of "an interaction of a lot of rare things that ultimately come together to affect a small percentage of the population." Those could include different fuel mixes and the way the vehicle is driven, he said, though he did not explain further.

Lee said there are limits to the percentage of Pentastars that will experience the malfunction because of the variables involved.

"You have to have this fuel characteristic, you have to have this drive cycle--and all of these things have to line up in order to have this situation occur," Lee said. "That's why" the number of potentially affected engines "is so small. If it were a design defect, or if it affected [a basic component] like the integrated exhaust, we'd have issues on everything, which we don't."

The National Highway Traffic Safety Administration says Chrysler has not issued a technical service bulletin on cylinder head failures with the Pentastar engine.

The company is fixing all affected engines under warranty.

The stakes are high for Chrysler because the 3.6-liter Pentastar V6 powers many popular vehicles behind the automaker's string of 28-straight year-over-year monthly sales gains.

The engine is standard in the Grand Cherokee and Wrangler, Chrysler 300 and Dodge Charger sedans and this fall will be available on the 2013 Ram 1500 pickup.

Last month, Chrysler said it was ending production in September of its only other V6 engine, a 3.7-liter version that has powered the 2012 Ram 1500 and Jeep Liberty.

Since the Pentastar V6's debut in 2010 on the 2011 Grand Cherokee, the automaker has built the engines at two North American plants--in Trenton, Mich., and Saltillo, Mexico. Last month, it announced that it would soon convert part of its Mack Engine complex in Detroit to begin producing additional Pentastars.

Chrysler CEO Sergio Marchionne said in January that the company's production plans require at least 1.2 million copies of the 3.6-liter V6 a year. The company also is working on a smaller-displacement 3.2-liter V6 variation for future models.

The engine problem shows up in consumer complaints filed with NHTSA on the Jeep Wrangler. So far, a dozen owners have reported a ticking sound coming from the left side of their Pentastar engines, stalling, loss of power or misfires coming from cylinder No. 2.

Postings on allpar.com, a Web site popular with Chrysler technicians and product enthusiasts, also identify cylinder No. 2 as a problem related to the head malfunction. The No. 2 cylinder fires second in the engine's ignition sequence.

Posters on allpar.com and Chrysler dealers contacted by Automotive News say the cylinder-head issue isn't limited to Pentastars installed in Wranglers.

Similar issues were reported with Pentastar-equipped Dodge Journeys, Chrysler Town & Countrys and Dodge Grand Caravans, though no NHTSA complaints on the problem have been filed for those vehicles.

Chrysler's Lee said the NHTSA complaints concerning the ticking noise may or may not be related but that generally a ticking engine "is not an indicator" of the issue.

By Larry P. Vellequette- Automotive News