1999 Jeep Grand Cherokee 4.0 overheating after changed thermostat, coolant low light is on, check engine light, and check gauges lights are on.

Sounds like your water pump is going bad.

Even though I hear no noise, have no leaking, or any other issues besides what I stated? I don't want to take off the water pump just find out that its not the issue. I mean unless I have too.

Try and see weep hole on water pump. If it has any signs of leakage no matter how small I would replace it. Other than that there are a lot of different things it can be causing this issue. Radiator stopped up, bad radiator hoses(collapsing under pressure), faulty thermostat or installation, bad radiator cap, blown head gasket, bad or faulty radiator clutch fan(if applicable) and the list can go on.

How can you tell if the radiator is stopped up? I only have seen the radiator hoses collapse after it had gotten really got and I was pulled over the first time it over heated. We're putting another thermostat in now, after it sat ffor 14 hours I didn't see any water around the head or anywhere near the water pump or on any pulleys or anywhere on the engine or ground. What else could be wrong your helping me out to at least check things that could be wrong off the list! Thanks

The weep hole on the water pump may not be wet looking. It might only have signs of dried anti-freeze around it. If so it needs to be replaced. A small inspection mirror might help get a better look at the weep hole.

I was just at autozone and a mechanic overheard me telling someone what my issue was, and said since I have no leaks and changed the thermostat, and the fact that I had water boiling under the radiator cap that it sounded like a blown head gasket maybe because it was run too hot? How does that sound and is that hard to change on a 1999 jeep grand Cherokee 4.0?

First of all, yes it is possible to have warped the cylinder head from overheating. However, these Jeeps are a pain to bleed all the air out of the cooling system. Since you mentioned the low coolant light is still on I would bet you have an air pocket trapped in the cooling system. I always drill a small 1/8" hole at 12 o'clock in the new thermostat. This allows air bubbles to escape. Second, run the engine until hot with the radiator cap off. Once the thermostat opens your coolant leval should drop and you can pour more into the radiator and top it off. Pay close attention to the tempature of the air coming off the cooling fan. If it is ambient tempature air then you have an air pocket or no circulation of coolant. Once the thermostat opens you should get nice hot air coming off the fan indicating coolant flow from the engine into the radiator. Keep a check on coolant level over the next few days as it will "burp" air out and use a little coolant from normal heat up and cool down cycles until it is completely full. Also, cheap insurance to replace the radiator cap itself as it holds pressure which raises the boiling point of the coolant. Hope that helps. Tim

Yea this was helpful. I hope its not the head gasket, that will cause a lot of family issues for me beyond belief. If i leave it running with the radiator cap off and then water/coolant makes its way out the top of the radiator would that mean that the gasket is blown? i let it sit overnight and the overflow canister was at the fill line this morning it was empty. were going to put the thermostat back on now and retry everything you just said to do because I dont remember doing this last night. Thanks

So I did what you just said Tim and while the radiator cap was off and the jeep was running the water went down but like 2 seconds later came back up and overflowed. I let it run for like a minute and it did thatnlikem2 more times and then just stayed at the top pouring coolant out. I put the radiator cap on it and drove with the ac on for like 2-3 miles just to see what would happen and it ran hot 220-240 but when I got home putmitmin park I could hear it bubbling up so I let it run for another minutenor 2 and it never overflowed from anywheres or leaked so i shut it off. I guess it is still over heating and now check engine light stays on.

The water came back up and overflowed for one of two reasons. Either A the water is boiling internally around the cylinder wall and pushing air into the radiator or B the cylinder head is warped and your getting compression gases pushed into the cooling system. Are you positive the thermostat is installed correctly with the long side going into the cylinder head and not the housing? Secondly try warming the engine with radiator cap on to about 190 or 200 degree (before boiling, but enough to open thermostat) squeeze radiator hose to check if system is under pressure. If it is not, carefully loosen radiator cap and try to top off coolant level. If non of that works you need to have the head tested. They use a blue liquid in the radiator neck and take air samples. If the fluid turns pee color there is exhaust gas in the coolant system indicating a warped cylinder head not sealing against the block properly.

Positive, the thermostat wen came With a pre drilled hole with instructions to install it at 12:00oclock and that's what I did. I work at a crescent ford here in New Orleans as a porter so luckily I can get it looked at for a cheap price which imma do tomorrow or Tuesday. I'm sure they can run all needed test to let me know what is exactly wrong with it. I just don't want it to overheat and blow up on me on the way to work it's like a 30 mile trip mostly interstate.

Could rust cause overheating? I did a flush of the radiator and a bunch of rust came out. Its not the head gasket because they did the water test. When the heater is on the air never gets hot which is weird because its overheating....why wouldnt i be getting any heat when the heater is on?

if you have the 4.0 inline 6, BE CAREFUL. the head on the early grand's of that model are defective and if overheated too much will crack unless it has already been upgraded. have the head checked, if it has a stamp that says "0331" you will want to have it replaced after overheating as much as you said. if it is stamped "tupy" you should be ok on the head.

my radiator blew & we replace it today. Putting new hoses on it & filled it with antifreeze, now the antifreeze won't cycle through. It heats up steadily & I've run it with the heater running & it'll only blow out cold air. What can I do? What could be wrong????

These are horrible asnwers, look at the upper radiator hose over the A/C compressor, if you can squeeze it when hot, there's your air bubble. Am facing the same issue right now, nothing is leaking, nothing is plugged.

unhook the wires from temp sensor, remove radiator cap, park on a hill with the thermastat housing facing upward, carefully crack the brass fitting a little at a time until air stops and water comes out [ remember little by little it may be steam] refill radiator and replace cap you should now have heat!!! and no air in head.

are any of you guys making sure your using the recommended coolant , thermostat , and hose clamps.? The grand Cherokee has lots of sensors and using anything then The recommended mixture is 50/50 ethylene-glycol and low mineral content water. Never use pure antifreeze. Only Mopar Antifreeze Coolant, 5 Year/100,000 Mile Formula (glycol base coolant with corrosion inhibitors called HOAT) is recommended. This coolant offers the best engine cooling without corrosion when mixed with 50% distilled water. . Anything else will cause issues also the thermostat should be the factory 195 degree required part. And for the hose clamps there are different types of hose clamps and the ones you need are the constant tension clamps it's another factory part. Don't cut corners and get the right stuff

I'm switching all of my stuff over to factory for the most part and keeping my performance high flow water pump to cycle the dual core 42mm Australian radiator and the after market radiator cap. If this does not do the trick il start with the radiator cap and water pump being put back to stock

Hope this helps

I have 1996 Jeep Cherokee. Water pump blew or so I thought. Old Water pump definitely had leak from bearing drain (seep) hole. Actual 100% fail was the heater bypass valve passenger side near firewall. One of four plastic inlets "broken" off. So I replaced it (minor-pair of pliers job). While doing all this, the radiator cap was heavily gunked with some stop leak. Papa not happy now. After some minor driving, leaks! But not from pump, valve. I'm reading posts here & wondering about air, but I'm going to rule that out for now. The leak is from the radiator overflow hose. It's hard to get too. I may do a flush.... But I'm also going to change the radiator cap from 16 lbs currently to 14 lbs. The radiator "bladder" isn't overfilling. The pressure does fall rapidly once engine is OFF. Too rapidly. I'm pretty sure there's a stop leak buildup issue somewhere else. But my heat is awfully feeble too so I can't rule out water pockets. Thermostat seems ok. When I 1st started had to wait 3-5 min. to fill another ?gallon? I'm going to do only short trips for now. Overheat light stays off. I'll be carrying spare water again (prior to this minor use there-water pump I'm sure.) Prior to this too the heat never fully turned off. I'm putting this in as answer because I wish to notify some folks about that heater bypass valve near firewall. Tho I'm a if-it-works-don't-fix-it type, now that I know I'd recommend replacing that with the water pump. 2/3 co$t of pump about (or 1x for cheaper rebuilt pump) But for this minor leak-from overflow hose I'm open to opinions. I'm sure of issues including that hole in thermostat, so I'll be inspecting that next. Also, the overflow valve regulator. I generally don't "flush" (don't fix it if not broke) but obvious overuse of stop leak ... What do you all think? 1996 Cherokee, 2.5L- 2 WD Made a video. May post online after editing. Mainly started video over serpentine belt replace (an upside adjuster+loosening idler deal) it's not shown anywhere I looked online.

Some time in life we get all crazy,it could be the head gasket. It could be an apple in the carb.look you are overheating have the radiator flused and clean.there are chemicals they put in that eat away all the gook.fresh straight antifreeze.the15.00 type.go find your apple my friend

Not real sure why the cooling system on an automotive gasoline engine Is still filled by pouring coolant into the reservoir? They make vacuum fill tools that are not very expensive and it doesn't require that much performance from an air compressor to pull the vacuum efficiently. Get a good 28-30 inhg vacuum on the system, and let it pull the coolant in, this will effectively remove and/prevent air pockets altogether. Im a diesel mechanic and we have been vacuum filling cooling systems since the first few years of EGR systems to prevent air pockets in EGR coolers that were causing cracks there. Very simple, quick, clean, and effective.

I have a 1998 Jeep Cherokee Sport 4.0 on my overflow jug the little nipple that the Overflow hose goes into The Jug broke off can I just plug that hose and be okay until I change it

Do I need the over flow jug can I just plug the hose till I can replace the jug

the overflow jug is actually an expansion tank that has a couple of functions besides being a visual indicator, one of which is a place to hold coolant when it gets hot and expands by plugging the vent tube you risk having the radiator cap venting and or causing extra pressure in your cooling system which can cause problems also the expansion tank aids in purging air from the system. bottom line yes get a new tank they are pretty cheap at the junkyard and you don't want to cause yourself more issues

I’ve been having problems with my 1999 Jeep Cherokee temperature. It use to over heat but I changed the water pump upgraded the radiator changed the thermostat and sensor And Now it does not over heat but the tep still goes to is 220 any one having the same problem or might know what it is?