Smoking / knocking after water pump failure
Help! What have I done.
My water pump bit the dust and threw the serpentine belt clean off. I replaced both and fired it up.
I was letting it warm up so I could add more fluid to the bottle when it started smoking. I chalked this up to water I spilled when blowing out my heater core.
Then the white smoke started billowing and it started making a horrible knocking sound. The smoke is coming from the right side near the exhaust manifold. The electric fan kicked on at 210 but I don't think the thermostat clicked over. It didnt drink any more coolant which struck me as odd. When I shut it off, the oil pressure is lower than I had ever seen it.
99 Jeep XJ 4.0
15*,***
Oil on the dipstick looks normal
Started up fine, oil pressure good.
My water pump bit the dust and threw the serpentine belt clean off. I replaced both and fired it up.
I was letting it warm up so I could add more fluid to the bottle when it started smoking. I chalked this up to water I spilled when blowing out my heater core.
Then the white smoke started billowing and it started making a horrible knocking sound. The smoke is coming from the right side near the exhaust manifold. The electric fan kicked on at 210 but I don't think the thermostat clicked over. It didnt drink any more coolant which struck me as odd. When I shut it off, the oil pressure is lower than I had ever seen it.
99 Jeep XJ 4.0
15*,***
Oil on the dipstick looks normal
Started up fine, oil pressure good.
Last edited by jmsummers2012; Oct 1, 2015 at 03:46 PM.
Seasoned Member
Joined: Aug 2015
Posts: 404
Likes: 18
From: New Jersey
Year: 2000
Model: Cherokee
Engine: 4.0L
When the water pump went did the engine overheat? or did you shut it off right away?
From the sounds of it you blew the head gasket, a compression test or leakdown test would tell you for sure. Most auto parts stores rent both of those testers if you don't own one or want to buy one (although harbor freight has cheap ones). That will tell you if your head gasket is shot without having to pull the head.
Your thrermostat is probably fried from the heat, or age, but I'm leaning towards the head gasket because of the knocking noise.
From the sounds of it you blew the head gasket, a compression test or leakdown test would tell you for sure. Most auto parts stores rent both of those testers if you don't own one or want to buy one (although harbor freight has cheap ones). That will tell you if your head gasket is shot without having to pull the head.
Your thrermostat is probably fried from the heat, or age, but I'm leaning towards the head gasket because of the knocking noise.
I overheated it after installing the new water pump... air bubble or gummed up thermostat prevented the new coolant from moving about.
I tried a chemical block tester and that came out fine.
It drove about 10 miles today and it seemed strong. No problems. No smoke. No knocking. (It was a top end sounding knock that lasted about 10 seconds before I shut it down)
I'm going to drain the coolant and oil tomorrow and make sure they are not mixing.
Might have dodged a bullet. The white smoke is whats got me nervous.
I tried a chemical block tester and that came out fine.
It drove about 10 miles today and it seemed strong. No problems. No smoke. No knocking. (It was a top end sounding knock that lasted about 10 seconds before I shut it down)
I'm going to drain the coolant and oil tomorrow and make sure they are not mixing.
Might have dodged a bullet. The white smoke is whats got me nervous.
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CF Veteran
Joined: Jul 2013
Posts: 7,554
Likes: 17
From: Monett, MO.
Year: 1999
Model: Cherokee
Engine: 4.0
Oil is definitely in the coolant.
The exhaust is blowing water vapor
I have metal shavings and black particles on the dipstick.
Is it time for a new engine? Or is there a possibility that I could fix whatever got damaged?
The exhaust is blowing water vapor
I have metal shavings and black particles on the dipstick.
Is it time for a new engine? Or is there a possibility that I could fix whatever got damaged?
CF Veteran
Joined: Apr 2009
Posts: 4,734
Likes: 12
Year: 2015, 2012
Model: Grand Cherokee (WK2)
Engine: 3.6L
Or sell it with full disclosure. Might bring $1,000 to the right person.
CF Veteran




Joined: May 2012
Posts: 7,965
Likes: 964
From: Lost in the wilds of Virginia
Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
Yep. Or a rebuild, if the block isn't cracked.
Yep. There are two methods. Replace or rebuild engine.
You probably didn't have the cooling system full, ran it that way, and kablooey.
Yep. There are two methods. Replace or rebuild engine.
You probably didn't have the cooling system full, ran it that way, and kablooey.
There is really no way for oil (other than automatic transmission fluid) to get in the coolant. When it threw the belt was the idler pulley seized?
CF Veteran
Joined: Apr 2009
Posts: 4,734
Likes: 12
Year: 2015, 2012
Model: Grand Cherokee (WK2)
Engine: 3.6L
Seasoned Member
Joined: Aug 2015
Posts: 404
Likes: 18
From: New Jersey
Year: 2000
Model: Cherokee
Engine: 4.0L
If it wasn't for the metal shavings I would say just replace the head gasket and see what happens, but metal in the oil means it's been in contact with all the bearing surfaces. No bueno.
You could still rebuild it with new bearings and everything or find a good used one. Or sell it as someone said
You could still rebuild it with new bearings and everything or find a good used one. Or sell it as someone said



