BOSTON -- Ford Motor Company is taking a closer look at its newer vehicles following a Team 5 Investigation into defective valve stems.

"If you see cracking at all on the valve stem, you know you need to replace it," said auto safety expert Sean Kane.

What To Look For | Photos: Spotting Defective Valves | Watch Report

A valve stem is a 50-cent part that allows you to pump air in your tire, but if cracked, could cause you to lose tire pressure and control of your car. A Florida man died in a crash last November. Investigators blamed a defective valve stem.

Team 5 Investigates first reported on defective valve stems in June after millions of Chinese-made stems were recalled. Our investigation found cracks in the valves stems on replacement and new tires, including on two of WCVB-TV's 2007 Ford Explorers.

At the time, Ford refused to acknowledge a defect or confirm if the parts came from the same plant in China. Friday, Ford told Team 5 Investigates that it has opened an investigation.

"We have seen reports of cracked valve stems," company spokesman Wes Sherwood told Team 5 Investigates' Susan Wornick. "We are investigating these and others NHTSA has published."

But he added in a statement, "Stems in Ford vehicles are made with a different material formulation."

So far, the National Highway Safety Administration has neither opened a formal investigation into where the parts on newer Ford vehicles were made nor issued a recall --- steps that Kane said are crucial.

"I think we're sitting on a ticking time bomb," he said.

Citing 35 recent failure reports on 2007 and 2008 Ford vehicles, Kane wrote a letter to NHTSA explaining that "Ford is a standout among valve stem failure complaints" and asking for immediate action.

"I think the time issue is critical right now because we're getting to that point where the stems are going to be failing much more rapidly," Kane said.

Ford did not reveal which models are involved in its review, but no matter what kind of car you drive, check your valve stems. If you see cracks, replace them immediately and save the old ones in case of a recall.