My girlfriend has a 2003 Montana that is having a coolant problem. Back in January, the water pump was replaced because coolant was being sprayed on the belt area. While that was happening, she had to add coolant to the overflow reservoir every other day or so. After the water pump was replaced and air was purged from the system, it seemed to hold the coolant fine. I was checking over things yesterday and noticed there was no coolant in the overflow reservoir so I took off the radiator cap. Not only was there no coolant to be seen but there was brown goop all around the filler neck. The van hasn't been dripping any fluid. She just drove the vehicle on a 2-hour drive earlier in the day with no overheating issues. Is this engine prone to blown head gaskets? Where is the coolant going and how do I pinpoint this before tearing into the engine? Any help or suggestions would be much appreciated.
Coolant disappearing
- Thread starter waldreps
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The V6 is known for leaking lower intake manifold gaskets. You can try a compression test to make sure it's not a blown head gasket but either way you have to start disassembling the top of the engine. The brown stuff is the result of oil and antifreeze mixing. Do not drive the vehicle, you will cause further damage.
I'm having a similar issue. 153,000 miles. I know I'm leaking coolant from the Thermal Valve Bypass because of an o-ring (1:06 mark of this video: https://www.youtube.com/watch?v=PRoptTtrMKc). Looks like I may also be leaking from the bypass hose as well. I wonder if you can smell coolant when you drive it after filling it up?
Do leaking lower intake manifold gaskets allow oil to get into the coolant? The engine oil looks good with no milky appearance at all so I don't think coolant is getting into the oil. Swenny, I don't really smell coolant too much and there is nothing dripping. I also don't see any evidence of leaks around the engine compartment.
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Here's a good explanantion of it: http://www.northwoodgarage.net/5074/plastic-engine-parts/
Thanks for the link. I hope that the intake manifold gasket is all it is. The description of a slow leak without any evidence of a leak seems to fit. There is no evidence of coolant getting into the engine oil. There is goop in the radiator and overflow reservoir but I'm thinking that could be from old Dex-Cool. I've read a lot about it turning into brown goop if it's not changed regularly. I have a repair manual on the way but would love to see a write up of this job by someone who's done it if anybody knows of one. I would like to know what tools and parts I need before doing it.
Zimgxp
New member
Yes the brown goop is from the dexcool. Oil and water is a lighter mixture, kind of like a butterscoch milkshake
Ok, I have an update. I haven't had time to get into a permanent repair so for the time being, we decided to add coolant and drive it for a few days to see just how fast the coolant disappears. My girlfriend added coolant to the radiator(she said it didn't hold much) and to the overflow reservoir. She drove it yesterday with no problem but today, the temp gauge went into the red and the warning light came on. She pulled over and shut it off. After looking at the engine, she noticed that the overflow reservoir appeared to be full and under pressure as if it was going to explode. Does the system just have air in it from being so low on coolant or is there something else wrong? Any ideas or explanation?
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Steelcity
Member
FYI: I have an 03 and it Does not have a pressurized overflow cap/tank. The rad has a pressurized cap .
Zimgxp
New member
Does it boil in the tank. If it does it might be a head gasket. Checkintg the coolant for hydrocarbons will verify if it is or not.
Ok, another update. Apparently it was just air in the system from when my girlfriend didn't follow my refill instructions. I got the van and opened the two bleeder screws, added coolant to it, closed the screws, let it run for a bit, then checked it again and added a little more. Then I drove it around with the A/C running for a while and it never made it to halfway up the temp gauge. I'm pretty sure the goop in the radiator was leftover from the Dex-Cool not being flushed out of it before they put regular coolant in there instead. I do believe the intake manifold gasket is leaking but I will address that when I have an idea just how quickly the coolant is disappearing. There is no coolant in the engine oil as the oil looks great. It took about a month and a half for the coolant to get as low as it did when this problem started so I'm going to watch it and see how quickly it disappears to determine how bad the problem is. Thanks for the replies.
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Ok, another update. I bled air out of the system using the bleeder screws and topped it up with coolant. After doing that, the van didn't overheat even with the air on and driving for 10 or 15 miles. That seemed to do the trick and worked for about a month now. We've been keeping a close eye on the coolant and have only had to top it up once since then so the coolant leak is pretty small. Today though, the van overheated on my fiancee's way to work. She got a light on the dash that said overheated coolant and the engine went into a safety mode that alternates cylinders firing. I'm on my way there in a bit to see what I can do for her. The coolant level should be fine since we checked it only a few days ago. The only thing I can guess is that the thermostat is stuck. I did have her turn the heat on max while she was limping to work in it and she said it was blowing cool air not warm. She only drive about a half a mile with it like that cause she didn't want to walk. Would everybody agree that it's the thermostat? Any other suggestions?
Well, when I got there, the first thing I did was check the coolant. The overflow reservoir looked fine and right at the full line. I opened the radiator cap and all the coolant from the overflow reservoir rushed right into the radiator. Why would that have happened? If the coolant was low in the radiator, why didn't it already suck the coolant from the overflow reservoir? Isn't that the idea? Anyway, it still needed more so I opened the bleeder screws and topped the radiator and overflow reservoir off. The vehicle worked fine. Why did this happen? Is air getting in the system and preventing the coolant from being brought in from the overflow reservoir? Should I just start ignoring the overflow reservoir and check the level in the radiator from now on? Any ideas? By the way, after doing this, it works fine again. So, how do I prevent this from happening again?
Steelcity
Member
If you have rear heat/ac then that would explain why it is so hard to bleed. plus if you do have rear heat maybe that is where you have a small leak but you never think to look under the van in the back??
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The radiator cap looks like it's the stock one. It's a 15lb cap and does have the two gaskets as you described, melsg5. Steelcity, this van does have the rear heat/ac but I would think a whole month of things working fine and then it overheating again because of what seems like an air locked situation where the coolant system just want suck in extra coolant from the overflow, seems wrong. I just don't understand why coolant wouldn't be getting drawn in from the overflow reservoir.
I have done neither. I'm not sure how to test it for hydrocarbons and just haven't rented the pressure tester for it. I thought it was fixed each time except for a small leak somewhere and then it overheats again because it won't draw in coolant from the overflow reservoir.