4.7 HO overheating and rough idle - JeepForum.com
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post #1 of 38 Old 07-09-2014, 08:28 PM Thread Starter
Knoxes
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4.7 HO overheating and rough idle

I have a 2004 Limited with about 110K miles. I've had it for about 3 years and 40K miles, with no overheating issues.

Started overheating after towing the boat (3K lbs) for about 3.5 hours last weekend. I caught it before it got too hot and was able to bring it back down with the heater.
Ran ok most of this week, even towing short distances, but started idling roughly over the last couple of days. And started running hot again in traffic (without the boat) today. The reservoir looked a bit low, and I have been able to add about a gallon of distilled water split evenly between the reservoir and directly into the radiator. The top hose is soft when it's cold. No foaming around the oil filler. And no clear signs of leaking. The fan seems to be operating properly, but it's hard to tell for certain. I think that I've heard some gurgling sounds from the heater core, but I'm not positive about that.

Any ideas before I take it into the out-of-town dealer tomorrow?

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post #2 of 38 Old 07-10-2014, 12:21 AM
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Short of diagnostics, you can try a computer reboot

Quote:
Originally Posted by Knoxes View Post
I have a 2004 Limited with about 110K miles. I've had it for about 3 years and 40K miles, with no overheating issues.

Started overheating after towing the boat (3K lbs) for about 3.5 hours last weekend. I caught it before it got too hot and was able to bring it back down with the heater.
Ran ok most of this week, even towing short distances, but started idling roughly over the last couple of days. And started running hot again in traffic (without the boat) today. The reservoir looked a bit low, and I have been able to add about a gallon of distilled water split evenly between the reservoir and directly into the radiator. The top hose is soft when it's cold. No foaming around the oil filler. And no clear signs of leaking. The fan seems to be operating properly, but it's hard to tell for certain. I think that I've heard some gurgling sounds from the heater core, but I'm not positive about that.

Any ideas before I take it into the out-of-town dealer tomorrow?
Did you get any codes? You might try disconnecting the negative battery cable, but then it would erase any codes helpful to the techs.

Happiness in our lives consists not in the absence but in the mastery of our passions.

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post #3 of 38 Old 07-10-2014, 05:09 AM
pdpunome
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Check passenger floor for wetness. If you have a radiator pressure tester that would expose a leak. Pull all of your plugs. I just had one in I serviced for overheating and it came down to a broken spark plug because the diy'er put two wrong plugs in.
Also I would add coolant not just water as the 4.7s are very sensitive to heat.

If you have a compression tester that would expose a blown head gasket.

Tools would be under 100 which is one hr of labor at a dealer so savings is dramatic in comparison to get the tools and test yourself.

2000 4.0 Selec Trac
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post #4 of 38 Old 07-10-2014, 05:32 AM Thread Starter
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Not getting any CELs. And the passenger floor is dry.
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post #5 of 38 Old 07-10-2014, 07:20 AM
capthowdy575
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Pull the plugs check for coolant on plugs also go to autozone and rent a test kit to see if you have exhaust gas mixing with your coolant. If you have any of these it's means you have a bad head gasket or a crack head. More likely a bad gasket. Also don't overheat our let it even get to hot or you will wrap your heads and they don't have a lot of tolerance so they really can't be machined.
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post #6 of 38 Old 07-10-2014, 08:01 AM Thread Starter
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It just threw a Cylinder 1 misfire on the way to the dealer. It's in their hands for now...
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post #7 of 38 Old 07-10-2014, 08:10 AM
capthowdy575
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By threw a cylinder you mean it came out the block our the cylinder started to knock. Also if you want to sell it let me know
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post #8 of 38 Old 07-10-2014, 08:32 AM Thread Starter
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threw a Cylinder 1 misfire=Check engine light
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post #9 of 38 Old 07-10-2014, 10:06 AM
capthowdy575
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Usually when people say threw a cylinder it's means that the actually cylinder is off the crank our bad journal bearings. The misfire is probably due to coolant fouling your plugs
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post #10 of 38 Old 07-10-2014, 10:13 AM
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I had a similar issue lately with an unsolvable one: rough idle, loss of power, overheating, etc. Turned out to be the catalytic converter. It wasn't showing a code for it cuz the vehicle wasn't running.

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post #11 of 38 Old 07-10-2014, 10:15 AM
capthowdy575
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To check the cats start the car and take a temp prob and read both cats at normal operating temp check the fsm to see which they should be
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post #12 of 38 Old 07-10-2014, 10:51 AM Thread Starter
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The dealer has been pretty good so far. Their communication and methodology seems pretty solid. We both think that the water pump was replaced at some point by the PO. It's possible that the thermostat is bad, but I think that's unlikely because it does eventually cool down when you crank the heat on or get moving.

They are going to do a dye test now to see if any gas is getting into the coolant. That ought to be a pretty definitive test.

I had considered the cats, but I think it's unlikely to have caused the misfire. And it runs solid once the rpms gain above the idle.

Actually just occurred to me that we didn't talk about pressure testing the system. Just left them a message about that.
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post #13 of 38 Old 07-10-2014, 05:02 PM
capthowdy575
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Well I hope for the easiest and cheapest fix
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post #14 of 38 Old 07-11-2014, 10:11 AM Thread Starter
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It's the head gasket. Fuel in the coolant.

Estimate is $1300 if it's just the gaskets. If the heads are warped, it's $900 for one side and $1300 for the other. They are mulling over an offer for it as is, but I'm expecting a low ball. I could tow it home and have a go at it myself. Not sure how difficult it is or what those costs look like.
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post #15 of 38 Old 09-01-2014, 08:43 PM Thread Starter
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I rebuilt the top end. Had the heads decked .010, basic valve job, new gaskets, new water pump, some hoses, belt, etc. It's running fine, but seems to be running just a bit hot - hasn't really gotten over the 210 mark (maybe slightly), and seems to hold there even when left idling for some time. On the freeway, it's solidly below 210 - probably right on the 195 mark for the thermostat. But I'm not entirely sure that it's cooling properly. After the initial 2 hour drive home from the rebuild, it seems to have taken a bit more coolant from the reservoir. Concerned that I still have some problems here.
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