Questions and Answers

Ford Explorer Learned To Whistle Q. Vincent, Just found your column on the web and hope you can help me with a Ford Explorer problem. I have a 1997 UN Explorer XLS, V-6 4.0 liter automatic transmission, 95,000 Kilometers. When the engine is hot (above normal temperature) I get a distinct whistling comes from the engine.

The whistle is particularly noticeable when idling, it may happen at higher revs, it is hard to tell. This can happen after towing or on a hot day, 35°C (95°F) and above, if I stop the engine for ten minutes. If I stop towing or run the engine for a while, the whistling becomes less or stops.

Additionally if I stop the engine, let it sit for ten minutes and re-start, the engine rattles quite loudly. If I let it idle for a few minutes, the rattle stops. This can happen even on mild temperature days (25°C)

My guess is there is a intake manifold air leak that occurs when the engine gets overly hot. This would explain the effect of towing and the whistle after the engine is re-started after being stopped for ten minutes.

It may also explain the rattle, it sucks more air due to the leak and because the leak is on the manifold, the computer has trouble compensating and runs the mixture incorrectly or the timing wrong. As the engine gets back to normal operating temperature, the leak stops and all goes back to normal. The engine makes no rattling noises when cold.

Does this theory make sense and is there any known problems with Explorer's manifolds leaking???? Has anyone else reported similar problems.

Regards,
Colin
Adelaide, Australia

A. Your theory is plausible and I have seen many Ford 4.0s suck in intake manifold gaskets. Usually the gasket between the upper and lower intake manifold. If you spray a little carburetor cleaner into the intake and the engine smooths out, you have a vacuum leak.

If you can eliminate all the external causes of a vacuum leak, cracked hoses, cracked intake hose etc.) then I would think it's time to pull the intake manifold off.