Chernobyl Coolant Tank

[Jeff Ferguson]

Purchased high mileage KJ in Nov. for son's first car. Very clean, Renegade, lightbar, leather, all options, for $2 grand. Ran great 5 months, made upgrades to sound system etc. One of my changes was to replace OEM coolant tank because it was so rusty orange you could not see coolant levels. Bought one off ebay $39, fit perfect. One day son calls says check engine light flashing and some steam, so I do road service, check fluids, no issues drive home 30 miles, 5 miles from house steam from hood and the coolant tank is boiling like Chernobyl, violent action in the right side, venting steam like a locomotive!
I get on KJ forum & read about HOAT, water pump impellers, air pockets, and such. I replace thermostat, water pump, fresh HOAT, no improvement. Take to trusted mexhanic and 3 of 6 plugs have antifreeze on them. I have engine swapped with 3.7 with 100,000 less miles for $1,200, drives great, for a day, then the Chernobyl coolant tank erupts, voilent boiling and stream exiting vent hole.
Mechanic comes to house, everthing checks out, he notices cap on coolant tank rocks back forth (ebay tank) and says "there's the problem". Ordered Mopar tank ($91), installed, no Chernobyl episodes since.
Question: Did my zeal to have a clean coolant tank just cost me $1,200?

 

[LibertyTC]

If 3 of the 6 spark plugs had coolant on them, were the 3 with coolant all on the same side as the coolant tank? Or was this a situation of a blown head gasket?
A pressure test would have found the leak at reservoir.

 

[tommudd]

Cheap is expensive

 

[Jeff Ferguson]

Two wet plugs were on left head, one on right. cleaned them off, ran great for about 10 minutes then began to shake and be under-powered. Diagnosing mechanic said he wouldn't work on the engine as it was 15 hours book time and such high mileage. Found local Jeep mechanic that had 3 wrecked Liberty's, motor taken from one of them. Agreed on pressure test, seems like such a delicate system that air can "block" coolant flow. Prior owner had stripped the 8MM allen set screw so we never confirmed air lock. Forgot to mention a new radiator went in along with the engine swap. Thanks!

 

[Jeff Ferguson]

New Mopar Tank behaving after several hours use!

 

[HoosierJeeper]

I'd say yes. Mopar is the only option for cooling system parts on these.

 

[Jar]

If it was not over heating; you should have changed the radiator cap first. New MOPAR tank would have came with one. I just learned this myself. $8

 

[Jar]

New Mopar Tank behaving after several hours use!

My tank is stained orange from MOPAR coolant. May not be rusty unless it only had water in it.

 

[JeepJeepster]

Surely a mechanic didnt recommend replacing an engine based solely on coolant on spark plugs?

Funny, I just replaced my coolant tank with a new mopar unit so it wouldnt look so stained.... My coolant is now yellow (zerex G05), so Im wondering if it will stain again.