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2003 Dodge Caravan - thud just as engine fires on startup

My very used 2003 Caravan (bought on auction) is about 275k miles, with remanufactured 3.3L V6 engine replaced and transmission rebuilt about 30k miles ago. In Park, Reverse, Neutral, the sound is normal. But in Drive, stopped at a light, the engine just “wants” to go, and kind of groans while stopped. Putting in neutral stops the groan, and less brake pressure needed. Also, letting up a bit on the brake at stop also reduces the sound.

Recently, when starting, it fires up quick as it always has, but the first time in the morning, there is often a “thud” or “clunk” just as the engine starts (sometimes three in a row), and then no more unusual sound after that (except the groaning at stop). This sound scares me. But it does not do that at any other time. And it gets the nominal 18mpg city, and at cruise say 65 or 70mph, gets about 25mpg. And the cruise at speed shifts fine, same as without cruise. Rides nice, just rattling body parts inside which seems normal for its high mileage - just not sure why transmission and engine seem louder than other Chrysler vans I’ve had, and now this weird thud when the engine first kicks up - I don’t think it is the starter, since the thud occurs just as the engine starts, a second or two after I turn the key. In any case, it starts right up with just a short turn of the key.

The belt was replaced soon after got home. Now the idler pulley is chirping, and the power steering pump whines a bit, so I drive it very little and will get the pulley and pump replaced. Perhaps one of these makes the thud?

The oil and filter have been changed regularly, and the transmission fluid looks brand new - clear pink/red.

I replaced the oil pressure switch and battery right after I got it home - the old battery was just enough to get home, and the oil pressure light blinked some at stop lights (I put it in neutral and revved up a bit which turned off the light). When I replaced the battery and switch, the light has not come on since (except when engine not running). I will check the oil pressure to be sure it really is ok.

That thud scares me. Thanks all!

Don’t replace just the tensioner pulley, replace the tensioner.

I’m betting you have one or more broken motor mounts.


I am with @Whitey on the broken motor mounts

Yes the motor mounts - that makes sense! And the tensioner replace as well as tensioner pulley.

Thanks all!