JPXJMOAB

98 XJ 4.0 with the AW4

The radiator has some nasty looking coolant from the PO. Pictures will be posted later! It's always had a slow coolant leak I haven't been able to trace with a pressure tester. I added coolant yesterday, about 3/4 of a jug between the radiator and overflow bottle and everything seemed fine. It's always run at operating temp no problem and still does. Now my concern is after I added the coolant yesterday I smell coolant when defrost is turned on.. I can't see or smell and coolant on the passenger carpet, can't see and coolant on the firewall. Only sign I have is the smell of coolant when defrost is on. I really hope it's not a heater core but any help would be awesome! Thanks guys

6Cylinder

A pressure test and putting dye in the system will be the only real way to see if there is a leak at the core.

If it's brown fluid you're seeing In the coolant you may have oil in the system. This is symptomatic of a blown head gasket, cracked cylinder head, cracked block, and a few others I could scare you with.

Heater cores are a pain to get to so make sure your diagnosis is spot on before doing a lot of unneeded work.

JPXJMOAB

Picture. It's not thick or milky. It's the same thickness as coolant

JPXJMOAB

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drhoward1988

Flush that thing! Split it up. Engine, heater core, radiator.

JPXJMOAB

any advice on the best way to flush it?

6Cylinder

This.

JPXJMOAB

Heater core and radiator I can flush but how would I flush the engine on the 4.0?

6Cylinder

You can only thoroughly flush a block with a flush machine or constantly draining and refilling. The former being the most cost effective.

JPXJMOAB

okay thank you, I'll give that a try hopefully tonight

JPXJMOAB

Flushed everything except the engine. I need to bring it too my shop this week to use a machine flush. What should I look for hear if it's a cracked head or bad heater core? I only get a wiff of coolant for like 3 seconds when I turn the defrost on

Morris4x4Center

I could be wrong, but every time I see brown water like that, I get the impression the previous owner was running just water in the system with no antifreeze / coolant (for years). The straight water just rusts everything from the inside out.

I think people believe they are saving money by not buying antifreeze / coolant, but in the long run, it's going to cost way more to repair later.


Definitely flush that Jeep out. Turn the heater on and flush the heater core as well. Then refill with proper amount of antifreeze / coolant. Hopefully it will be ok over the long run.



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JPXJMOAB

we flushed the heater core and radiator last night however not the block. We plan to replace the radiator and all heater hoses in a few months. I have a feeling it's just rust but it also has some small chunks that are very small.. Not sure exactly?

tlang

I would agree that its just rusty old coolant from a previously neglected cooling system. To flush the block you can take the lower hose off the rad and the upper heater hose off the water pump and run lots of water from a hose or whatever through that way.

I had the same problem with mine when I got it. I ended up doing this several times and using that CLR stuff as well.

With the heater core issue I would like stated above 1) be absolutely sure and 2) use a pressure tester