I have a 1997 jeep with a weird knocking noise from the motor

Try to put head gasket fix may fix the problem,I did works.

White smoke? Coolant is getting in the cylinder and the white smoke is really steam. Sounds like you have a blown head gasket. Bad news is that it needs to be replaced...good news is that the inline 6 cylinder engine is one of the easier head gaskets to replace. I've never replaced a head gasket but did it on my Cherokee just three months ago. If you tag your parts and pay attention how they are taken off you can do it. The other option is to replace the engine as they are pretty cheap to get. Good luck.

the white smoke is from water burning inside one or more of your combustion chambers. that,s why its overheating, your water is leaking into the parts of your motor that it don,t belong. this is not good cause it means you either have a blown head gasket, cracked head, cracked block, or maybe all of them. you can try putting a can of liquid glass, or sodium silicate cooling system sealer, or one of many available sealers from any auto parts store that might fix it for a while, and might not.but you,(or the next owner if the sealer works and you can pawn it off on somebody else) are going to have to replace the broke stuff eventually.

Head gaskets do not make black smoke it is white and smells sweet, is that the case?

Two choice:
1. Inspect the Head Gasket; Cause: head gasket leaking coolant into cylinders
2. inspect the Engine; Cause: Cracked block leaking coolant into cylinders.

Coolant is not a flammable liquid, therefore a lot of coolant in cylinder creates starting problem. You should check your engine and the coolant system for this issue.

The first thing you can do is check the oil dipstick - you're looking for a milky brown color as opposed to a dark brown (normal) color for oil - unless you've recently had an oil change - then it will be like honey. If you don't see any discoloration - I would then look around the the bottom of the area where the valve covers are located - the valve covers sit atop the heads and if you have a "blown" head gasket - you may see evidence of water/coolant seepage. You can also take the vehicle to a mechanic, who can do a simple test using air pressure to isolate a potential gasket issue.

Good luck (remember rated this post).

The white smoke is from a blown headgasket, your coolant is leaking into one or more cylinders and that's actually steam that you see coming from your tailpipe.
When this happens, your coolant level drops (because it's pumping it out the tailpipe), your car overheats, and of course it will knock as it overheats. An overheated car is sluggish, as well.
Another bad thing that occurs by driving a car with this problem is that the coolant is washing the oil off your cylinder walls and your rings will tear up your cylinder walls as they self-destruct.
Head gasket replacement is not an easy fix nor is it cheap, and usually you'll need to get the head machined to make it perfectly straight again - heads warp from overheating. A good mechanic can do a head gasket replacement in a few hours.
Overheating can cause knocking.Your best bet is to replace your motor because usually the knocking noise is caused by a spun bearing which would cost a lot to repair.

Sounds like the timing is off. Re-check your timing marks. If it has a timing belt it may be a few teeth of and getting no compression. Why did you need to replace the head gasket? If you overheated the motor it may have cracked the head causing a weird noise, but I would start with the timing first. That is the cheapest test.

You probably messed up a rod or caused piston damage your going to need more than a head gasket usauly when you over heat a car you causing the pistonts to expand more then they need to causing scouring and exsisive piston ware by the sound of it and the year your better off replacing the whole motor or completely rebuilding the old one wich will cost more then a use motor! good luck!

You might have a blown head gasket. The milky oil is an indication of water getting into it, which would point toward your head gasket. You should have a compression test done.

the reason it getting hot when stopped is the fan relay is out thus not turning the cooling fan on,this is a time consuming job,the relay is located on the passenger side tip of the frame behind the headlight,the grill,headlights,bumper,and tip of the front fender has to be loosened up to get to it.
The relay is about 70.00 or so,the engine cools down when you drive as you are forcing air through the radiator to cool it down,as for the heater issue probably caused by boiling the anti freeze out ,
To make sure the engine is ok do a compression check to verify the headgasket and heads are ok,as for smelling the sweet smell which is antifreeze probably due to overheating and pushing the fluid out of the cap or tank.