2005 Jeep Grand Cherokee



December, 5, 2012 AT 9:02 PM

We bought a 2005 Jeep Grand Cherokee Laredo 4x4 with 85,000 miles on it back in May 2012. This is my third Jeep, so I was very surprised when the heater core went out in September, taking out the water pump and thermostat with it. We replaced the water pump and thermostat, which cost us $500. The mechanic unhooked the heater core and said it wouldn't hurt to drive it that way since it was going to cost us another $300, and we couldn't afford it. We drove it home with no issue. The next day, Saturday, we went to a larger neighboring town 30 miles away. On the way home, it started billowing white smoke out of the tailpipe. We went straight home and parked it. We called the mechanic on Monday morning and explained what was going on. I asked if it could possibly be the gasket seals, as it was driving fine until the way home and it was only billowing white smoke. He said no, it had to be a cracked block and that it would be very costly to see if it was the seals due to all of the censors in the newer models. We live in a very small town and only have one mechanic who is GM certified, so isn't extremely familiar with Jeeps. I am wondering what your thoughts are on this. I guess I thought if the block was cracked it would be smoking darker, as it would be leaking coolant, oil, and gas. Will it hurt the engine worse if I drive it the 200 miles to where my parents live in the city, so someone who is used to working on newer Jeeps can look at it and give me an idea of what's wrong along with an estimate. Right now it has sat in the garage unused since September when it started smoking, and I'm making payments on a vehicle I can't drive because the mechanic hear scared my boyfriend in regard to what is wrong with the Jeep. I would greatly appreciate and advice you may have for me.


3 Answers



December, 5, 2012 AT 9:33 PM

You need a new mechanic. First of all, heater cores spring leaks all the time, just ask any GM owner, and that does not damage the water pump or thermostat. The water pump can leak on its own, and thermostats do stick every once in a while but in general they are very trouble-free. There is nothing you can do to cause them to fail, including a leaking heater core.

You didn't say which engine you have but $500.00 for a water pump seems way too high.

Cracked block? Without even seeing it? A cracked block is so extremely rare, even after severe overheating. That is the last thing any professional would even think about looking for. I've run into one in my entire life, and I caused it in the '70s by leaving it sit in winter with only water in the cooling system, no antifreeze. I'm confident your block is not cracked. Your mechanic, ... I'm not so sure.

The typical progression of events would be the heater core was leaking, the coolant level got low enough to prevent circulation so the engine overheated, it wasn't noticed so the cylinder head(s) warped to the point the head gasket couldn't seal. The white smoke from the tail pipe is from burning coolant. It gets into the cylinders through the leaking head gasket, burns, and goes out the tail pipe.

"He said no, it had to be a cracked block and that it would be very costly to see if it was the seals due to all of the censors in the newer models."

There are very inexpensive tests to see where the coolant is going. A cooling system pressure test takes a few minutes. A cylinder leakage test takes longer but will show up as air bubbles going into the radiator or reservoir. There's also a "sniffer" test that checks for combustion gases in the cooling system. None of those require disassembling the engine. As for all those sensors on newer models, those have been around since the mid '80s. That's what we're trained to work on, but you don't do anything with them. When you replace a head gasket, the sensors come off with the cylinder head. There's no special procedures or things you have to do. You either need a new mechanic or you need him to learn how to communicate better. Either way, you need a second opinion.



December, 5, 2012 AT 11:27 PM

I appreciate your quick response and it has a 4.7L V8. He told us that when the heater core went, it overworked the water pump and that was why it overheated and ruined the water pump and heater. I know a little about the workings of engines, but not enough to discredit him. The worst part is the mechanic is friends with my boyfriend, and we had him on speaker phone when we were talking to him, so I'm pretty sure I didn't misinterpret what he said.

If it is the head gasket, can you tell me what an average cost would be for repair? I've never had to do that with any of my Jeeps before.

Also, would it harm the Jeep to drive it the 200 miles to my parents home in the city to get it worked on by their mechanic. I don't really trust this one at this point.

Thank you!



December, 6, 2012 AT 1:34 AM

I'd try a few shorter trips before I took it 200 miles. As long as the coolant keeps going out the tail pipe, or combustion gases go into the radiator, you can get by as long as you keep an eye on the coolant level. It doesn't take much of a leak to make a big cloud of smoke so you could very well make it 200 miles without adding any coolant.

What you don't want is a leak that lets coolant run into the engine oil. Antifreeze will melt the outer layer of the bearings. That won't happen right away, but over a short period of time. Once they start to disintegrate, you'll have bigger problems. Check the oil level before you start the trip, then again when you get there. If the level went up, the oil should be changed. The oil is normally changed anyway after doing a head gasket because little pieces of debris, and stray coolant can get into the passages and into the oil. If coolant is in the oil, it will be a milkshake-brown color.

You can also try loosening the radiator cap one click. That will prevent pressure from building up in the cooling system. That pressure helps push coolant through the leak into the engine. That pressure can also reduce the amount of combustion gases that go into the radiator. Those gases, if the leak is fast enough, can prevent the thermostat from opening which will lead to overheating. Thermostats open in response to hot liquid, not hot air. If the temperature gauge reads in the normal range, leave the radiator cap loose. That may reduce the cloud of smoke you leave. At slow speeds there might be coolant splashing from the loose cap but that is less likely to happen at higher speeds where natural airflow keeps the radiator and engine cooler.

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