BruceXJ

We've done a few long distance trips in our Cherokee XJ (2.5 i petrol) over the last few months, requiring the coolant to be refilled. I've done this, though noticed that we've acquired an engine rattle that sounds like it's coming from the exhaust area of the underside, seemingly only after the car has warmed up after about 10mins, and more commonly when we're facing uphill. It sounds like a bolt may have come loose, or even a small crack in a pipe that's hitting together. I am not familiar with a lot of mechanical terms and learning slowly what to look for, but in the short term are there any common/specific mechanical checks that I can have our mechanic look at that may have been a result of low coolant?

I've checked oil for any discolouration and looked for any seepage, all is fine. We do have a slightly stronger petrol smell than usual but otherwise car seems to be running fine. Jeep is a 1997 Cherokee XJ 2.5 i petrol and has done c.65k miles.

Thanks for any advice!

awg

Loosing coolant you need to identify what is causing that. If it is not leaking or steaming out somewhere, it may be consumed internally within the combustion process

This dilutes the oil, and can cause accelerated bearing wear, leading to internal engine noise

Things you can do;

use an engine stethoscope or rod to listen for where in the engine the knock is coming, pressure test the cooling system, dye test the cooling system, perform a compression test,
take off rad cap, fill to neck, start engine and idle to thermostat is open, there should be no bubbles (bubbles represent exhaust gases), test coolant for CO2, send sample of coolant or oil for analysis

Taking no action would be unwise imo

RockyMtn96XJ

The stronger gasoline smell may be a result of awg's comment. If there is even a small amount of coolant combining with the gas in any cylinder, the gas may not be combusting completely, and being sent out the exhaust.

BruceXJ

There doesn't appear to be any external leaks in the coolant system, so I'll give your advice a go and if the issue is internal and take it from there. Thanks a lot for your help, much appreciated!

RockyMtn96XJ

Just a "heads" up... I had a coolant leak on the passenger side between the head and block in a very common spot for the I6, but the motor still ran fine. When I went to replace the head gasket I could tell the gasket had split in between layers and some of the gasket was stuck to the head, and some was stuck to the block. Very stuck, not just sticky and peeled off. So the coolant was coming from in between the gasket. Maybe you have a similar issue, but opposite.... the other side of the block, and leaking on the inside from a water jacket into a cylinder.