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Matt Hardy
Matt Hardy, ASE Certified Technician
Category: Jeep
Satisfied Customers: 920
Experience:  ASE Master Auto Tech, ASE L1, Jeep/Chrysler Dealer Tech, 18 yrs exp
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I Have a 2004 jeep grand cherokee, overland. V8 4.7l.

Customer Question

i Have a 2004 jeep grand cherokee, overland. V8 4.7l. My jeep overheated yet antifreeze was full. Temp pegged in the red stayed there until i got off expressway. approx. 5 mins
yet didnt lose power until I got on offramp. Then truck stalled and wouldn't start. Let truck sit for over an hour and bled air out of radiator (from Previous work done with a bs mechanic) made sure more than enough antifreeze and then truck started up and had a knocking sound and rough idle. After 2 mins everything seemed normal,(no engine light & ran smooth) Tried to drive home from the shop and ended up after 10 mins with loss of power and a rough idle as I pulled over for 2nd time, the truck just started smoking from the upper engine area and knock sound.
At this point the temp never went over 210 yet, no antifreeze or water in oil and oil still at correct level and no metal flakes or anything? Please help.
I then called roadservice and had my jeep flatbedded to my mechanic and am awaiting a call.
Any ideas and or help greatly appreciated.
Submitted: 4 years ago.
Category: Jeep
Expert:  Matt Hardy replied 4 years ago.

Hello and welcome to JA.

How did you bleed the air from the system? What procedure did you use?

Customer: replied 4 years ago.
I opened the radiator and pumped the top hose of radiator to help bleed out the air from radiator.
Expert:  Matt Hardy replied 4 years ago.

OK...on 4.7L...whenever the cooling system is serviced, the air MUST be bled from the bleeder fitting which is located on the engine, right next to where the upper radiator hose connects. It requires an 8mm hex tool to remove the bleeder fitting. I learned this by witnessing another tech learn this...the hard way.

The system will never burp the air out otherwise.

I hate to be the bearer of bad news, but in most cases, when the engine overheats to the point that it runs poorly and makes noise, usually the engine has sustained serious damage.

Matt Hardy, ASE Certified Technician
Category: Jeep
Satisfied Customers: 920
Experience: ASE Master Auto Tech, ASE L1, Jeep/Chrysler Dealer Tech, 18 yrs exp
Matt Hardy and other Jeep Specialists are ready to help you
Customer: replied 4 years ago.

sounds terminal?

 

Expert:  Matt Hardy replied 4 years ago.

It does. The next step is to properly bleed the cooling system and retest for proper operation. The shop should check the usual things: thermostat, flow through the radiator, fan operation, etc. One thing that should definitely be done is a head gasket test. Any decent mechanic should have the inexpensive tester to perform this test. It uses a special fluid to check for the presence of carbon monoxide in the coolant, which would indicate a faulty/leaking head gasket.

Typically what happens is: engine overheats due to low coolant or another problem. This overheating causes the engine metal to expand too far, which creates a head gasket leak. The head gasket leak allows combustion gases to enter the cooling system, leading to 'air' pockets and additional overheating.

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