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Overheating xj...she's a hot one

B

bhansen99xj

NAXJA Forum User
Location
Beloit, WI
Hi guys.

First post on this forum!

I have an overheating issue and I'm looking for some advice/insight.

Vehicle: 99xj sport 4.0

New: Radiator, thermo, coolant

Symptoms: Rusty sludge coolant even after the flush. Temp @ 210, then suddenly spikes to 250+. Upper rad hose and heater hose is hot, lower rad hose and lower heater hose is cool to the touch. I flushed the heater core separate and it is free of blockages. I have no heat so I obviously have no flow through the heater core. @260+ I eventually fill the reservoir and start dripping out the over flow.

My guesses: Blown head gasket spitting fumes into the coolant system preventing proper flow. -OR- Water pump impellers have rusted away.

What it is not: Heater core, aux fan, clutch fan, rad.

I have not tried another thermo yet but I'm about to.

Anyone have any ideas/insight on this? My reach for help has not been answered very well. I'm an avid xj'er so I promise I'll be around :looney:
 
Symptoms: Rusty sludge coolant even after the flush. Temp @ 210, then suddenly spikes to 250+. Upper rad hose and heater hose is hot, lower rad hose and lower heater hose is cool to the touch. I flushed the heater core separate and it is free of blockages. I have no heat so I obviously have no flow through the heater core. @260+ I eventually fill the reservoir and start dripping out the over flow. QUOTE

This tells me that you probably have blockages in the coolant passages. Pull off thermostat housing and flush out the block. Heater core has no flow means the heater valve is either plugged or stuck. Lower radiator hose is cold due to lack of flow. Try just running the engine with no thermostat. Be sure to temporarily put on thermostat housing, refill, start engine and look into the radiator with engine running to see if you have flow. DO NOT DRIVE IT WITHOUT A THERMOSTAT!
 
1993 Red XJ said:
U could have a collapsed lower radiator hose.
Click to expand...

Can't say that I collapsed this...the spring is still in tact and it is firm all the way to the water pump.

I do have one other symptom. After heating up without the cap on the flushing tee I see a lot of heat coming out but very little, if any coolant spitting out.
 
You could try a another cap. Go get a pressure test with your local mechanic it only takes a couple of minutes it might be cheaper than throwing money at it.
 
1993 Red XJ said:
You could try a another cap. Go get a pressure test with your local mechanic it only takes a couple of minutes it might be cheaper than throwing money at it.
Click to expand...

LOL another detail I forgot...I replaced the cap with the rad and it is functioning properly.
 
Yeppers, the fact that the upper hose and heater hose are getting hot says the thermostat is opening. You can eliminate the new radiator as a blockage.
A hot upper hose and cold lower hose means:

1) Coolant passages in the head/block are obstructed near the water pump, starving the engine for incoming coolant.
2) Or the water pump is not pulling any coolant out of the radiator

I've heard of water pump impellers eroding down, it might be the only iron part in the engine that could rust to the point of disintegrating into pieces.
The only way that happens is major cooling system neglect.

A blown head gasket can pressurize your cooling system, well before the engine warms up. When the engine is fully cooled down, start it and let run a minute or two, and turn the engine off. Pop the radiator cap and check for bubbles.
 
Last edited:
92DripCherokee said:
Yeppers, the fact that the upper hose and heater hose are getting hot says the thermostat is opening. You can eliminate the new radiator as a blockage.
A hot upper hose and cold lower hose means:

1) Coolant passages in the head/block are obstructed near the water pump, starving the engine for incoming coolant.
2) Or the water pump is not pulling any coolant out of the radiator

I've heard of water pump impellers eroding down, it might be the only iron part in the engine that could rust to the point of disintegrating into pieces.
The only way that happens is major cooling system neglect.

A blown head gasket can pressurize your cooling system, well before the engine warms up. When the engine is fully cooled down, start it and let run a minute or two, and turn the engine off. Pop the radiator cap and check for bubbles.
Click to expand...

Well the rusty sludge in my system is pointing me to the corrosion of the water pump impellers to no existance. At least that is what I am hoping.

As far as neglect....well...I bought her 3 years ago from a dealer and instilled a little trust into them. Things seemed fine when I bought it and drove it. 3 years has been my normal timeline anyways for cooling system flushing/coolant replacement. No problems until now. I'm thinking I should have flushed and cleaned this thing out 2 years ago.
 
Before you throw money at it, buy some cheap vinyl hose at the hardware store to temporarily replace one of the hoses and watch the coolant flow, or lack of flow. This will tell you if your water pump is bad, head gasket, etc.
 
This whole issue was in fact the water pump. I will put up a pic tomorrow. There was nothing left of the impeller at all.

The pump is on....coolant is in...all is good!

Thanks for the help guys!
 
wp.jpg



This is what I pulled out of the 99. The bearing was perfect, but the impellers...well...you can see. Sorry for the crappy pic. Came from a cell phone.

Thanks everyone for your imput!
 
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