So if you saw my other thread a few days back, had an issue with engine temp not getting up to temp on my 99 xj. This was after a newly installed water pump. Changed out the failsafe stat (piece of junk) for a mopar and temp issue solved. However, now when I crank it something doesn't sound right. Has a "hollow" sound to it. Standing outside the jeep at idle sounds fine. Its only when I'm inside the jeep do I hear it. Mostly at start up. But while idling too just not as noticeable. I have checked every hose, clamp, etc and all is good. Jeep drives just fine. Engine temp normal. Heater working fine. Been checking coolant level past few days to make sure I don't need to add any and haven't needed a drop. Stumped! Any thoughts?? Thanks.

 

Flex Plate bolts tight? They can cause a noise while cranking. but a "Hollow" sound doesn't sound quite like it either, more info needed.

 

Im not sure what flex plate bolts are. Ill have to look that up. I know describing the sound as "hollow" is pretty vague. Not sure how else to describe it. It sounds a little louder now at start up. Inside the cab that is. Like maybe something isnt right in the dash or as the fire wall. Can it be something with the heater core? Is there a flap or something that might be stuck open from when I washed it out with water hose?

 

More info,or you are worrying over nothing.

 

Sure you put the right pump in? Maybe the impeller broke on the new one? Is it full of coolant yet? You have to keep checking it and topping it off. The wrong pump might have the impeller, driving the water the wrong way.

 

The flex plate is bolted on the end of the crank (large round plate with teeth all around it) and that is what the starter engages when you turn the key to the start position and the engine turns over. They come loose some times and will make noise but not quite like you describe.

 

I don't know if not burping your system could cause this sound. Maybe someone can chime in or you can try it if you didn't do it earlier.