97 Grand Cherokee Laredo: Heating problem.

[Steve_jeep]

I recently replaced my radiator, thermostat, the cracked thermostat housing, and the large upper and lower hoses for the radiator. The dashboard gauge still shows that the engine runs cold. After driving for a while and then stopping, upon starting the engine a short while later the gauge shows the engine at the proper temperature. Could this be the water pump? Also the cab doesn't heat up, but I assume that that is at least the blend door, possibly the heater core.

Any ideas?

[mastertech1964]

i would suspect air pockets trapped in the engine

[mastertech1964]

im curious why did you change all these items in the first place? you may also have a small crack in the cylinder head pumping air into the cooling system when its cold and its stops leaking when the head heats up and expands

[Steve_jeep]

I replaced the radiator because it was rotted and leaking, the thermostat because my cab wouldn't heat anymore, and the thermostat housing because it had a big leaking crack in it. The engine still doesn't seem to be getting up to proper temperature according to the dash, but that may be the coolant sensor. I've tried to "burp" the engine but to no avail. At this point I'm assuming that at a minimum the blend door or associated motor axle is broken, and the heater core is likely plugged with "stop leak" from walmart that I put in to plug the radiator leak.

[fredjacksonsan]

What temperature thermostat did you put in? If it's too low, it could cause the issues you're having. What temp is the gauge showing?

If it's not overheating, you do NOT have a water pump issue.

edit: plugged heater core could do it, just disconnect the hoses from it, and put your garden hose against one of the inlets....make sure it'll flow both ways.

[Steve_jeep]

I put in a premium thermostat from Napa. Good news though. Yesterday I put in new spark plugs, a new air filter (old ones were in bad condition), and back flushed the heater core with a garden hose, and holy crap the gunk that came out was nasty. It was all of that stop leak stuff. I flushed it until the water came out as clean as a whistle. Then I hooked everything up and kept the old hoses on there since they were in good condition, topped off the fluid, ran it for a bit and added some more coolant when it worked out the air bubbles. Now I'm proud to say that my Jeep has heat again! I'm not sure how I made it through last winter but now it's nice and toasty. I'm pretty excited that it was just that and not the blend door. Also I reused as much of the coolant as I could capture in one of those buckets with a spout on it, the coolant was new. Now I just need to focus on getting new tires, brake pads, shocks, maybe a u-joint, etc... But in the mean time I don't have to worry about winter weather. I bought a Haynes Repair Manual for some light bathroom reading for future repair projects.

Also the cooling system seems to be going up to proper temperature, so the coolant sensor is probably just fine.

[fredjacksonsan]

Score! Nice to know it was a simple fix.