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Unread 06-19-2010, 10:29 PM   #1
witness
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TJ cooling woes

I"ll try and make this quick.

I bought a 2001 jeep TJ Sahara, the heater core was leaking. It started out as small leak, pretty soon it go bad enough to install a heater core bypass. Before installing the bypass I checked the heater to see if it was working and it was not blowing hot air, however it was leaking. I just assumed the heater core was also clogged.

A short time after installing a bypass for the heater core, I was driving at highway speed when I noticed my temp gauge was pegged deep in the red at 260 degrees. I shut off the motor and pulled over. I found that the heater core bypass had failed, I assumed this was the cause of the overheating so I installed a brass fitting in place of the plastic fitting from the auto parts store. This was on June 12th. I also changed the oil and coolant this same day.

I have been continually having overheating problems since then.

Several days after replacing the coolant I checked my coolant levels and pulled the radiator cap, I noticed that the coolant looked terrible. It looked like it was full of dirt and rust. Like it hadn't been changed in several years. The overflow bottle looked like it had dirt in the bottom of it. I checked my oil, no signs of coolant, none.

Today I changed the thermostat, still overheating.

I'm thinking cracked/warped head, or a blown head gasket. I'm thinking the cause of the bypass failure was not due to a faulty part, but do a problem with the head.

My other theory is the bypass failure was due to a bad part. The rode-side fix resulted in low coolant and running hot; this built up pressure, causing my radiator to boil, shooting steam and coolant out of where the aluminium meets the plastic tanks on the the top of the radiator. When I flushed my coolant I had the heater core back in line, so whatever was clogging it made its way into the system. Basically I think I need a new radiator.

So my options are;

1: Replace radiator
2: Swap in a non 0331 head

Any bets on what the problem is? This jeep has been a mall crawler all its life, so off road abuse is not a cause, nor does it lead me to believe the head is the weak link here. Being that its a 0331 head, I suppose anything is possible.

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Unread 06-20-2010, 07:13 AM   #2
Dryseals
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I think you're right and I would be looking for a bad head gasket.
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Unread 06-20-2010, 07:28 AM   #3
dwilliams35
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Not trying to be a smartass here, but are you sure the water pump's working okay?
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Unread 06-20-2010, 07:44 AM   #4
little_Jeep
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You have a 2001 TJ with how many miles on it? The OEM radiators are known to rot from the inside out..... the water pumps are known to fail from the inside out.... I suspect that your heater core rotted from the inside out then when you by passed it, your cooling system was able to get upto coorect pressure which wasn't good for all the rot in your radiator... If you had a head issue, I would think that you would be losing coolant. Are you? I think your entire cooling system probably needs a good flush and lots of work (new parts).
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Unread 06-20-2010, 02:16 PM   #5
greenrover
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The same crap/rust that clogged your heater core has clogged your radiator.
Get engine close to normal operating temp, when t-stat opens top hose will get nice and hot....after a few seconds the bottom hose should go from pretty much cold to warm/hot if all is flowing nicely. With that said you still might have enough of a clog to restrict flow and have a hot lower hose.
If you think you have a blown head gasket, then either coolant will be visible in a cylinder which will hopefully leave you a clue on a sparkplug. If hot air from cylinder is getting into coolant then I'd think you'd be boiling way over into your overflow bottle or worse....any white steam in exhaust after operating temp is reached?
If it were me....I'd get a new rad, and do a thorough system flush while bypassing the old rad and heater core.
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Unread 06-20-2010, 03:11 PM   #6
witness
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I swapped in a new ready-rad that my neighbor gave me. NIB. I figured it couldn't hurt.

Flushed everything real good while it was all apart, also went ahead and changed the belt and hoses while it was in there.

After the swap I started her up and drove around for about 30min. Seems to have fixed the problem. I hope it's not a temporary fix but I'll find out soon enough.

I'm going to go ahead and order an 0630 head and a 98 exhaust manifold and swap it on. I'd like to have those parts anyway for my Mojave trip in october. It's a long haul from south louisiana, so she needs to be reliable.
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Unread 06-20-2010, 03:22 PM   #7
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Quote:
Originally Posted by witness View Post
and a 98 exhaust manifold and swap it on.
Why? The 2000 and newer exhaust manifold is so much better...
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Unread 06-20-2010, 04:42 PM   #8
witness
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From my understanding the exhaust manifold from a 2001 doesn't match up to a 0630 head.

Now that you mention it, I may be very wrong. I'll have to look it up
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Unread 06-20-2010, 04:51 PM   #9
Knuckelhead
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Quote:
Originally Posted by witness View Post
From my understanding the exhaust manifold from a 2001 doesn't match up to a 0630 head.

Now that you mention it, I may be very wrong. I'll have to look it up
The exhaust manifold from a 2001 4.0L will match up to any TJ 4.0L head...
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