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Coolant issues

3K views 16 replies 8 participants last post by  Tomvw 
#1 ·
I like to be detailed with my descriptions so sorry if this gets a bit long.

History: About 40K miles ago I was having a cooling issue that I determined to be a faulty thermostat. I replaced it along with the timing belt and water pump. Sometime around that same point I replaced the coolant tank because of a small crack in the bottom of it. About 6K miles ago I noticed the coolant tank was at the minimum mark. I topped it off with G12 and it seemed to be fine. A short while after this I had one of the coolant lines to the oil filter housing fail. I replaced both lines and it has been okay since.

Current situation: Took a long trip in the car this weekend. Saturday I (after checking all fluid levels before I left) drove for 6 hours straight without stopping. About 400 miles. Temperatures have been mild this weekend so I hardly used the heat. *I live in PA and we've mostly been experiencing normal winter weather up until this weekend* For some reason I didn't check fluids before my return trip home today. About 3 hours into the trip the temperature gauge began to rise quickly so I pulled off the side of the road, let it cool down, and topped off the coolant tank with water (all I had on the road). The car functioned normally for the next two hours, then it did it again. This time I heard a strange noise coming for the dash (suspect heater core area). Again I pulled off the road, let it cool down some, and then topped off the tank again. Now I'm really paying attention to noises and gauge levels and also tried the heat. I'm getting intermittent heat, noises from the center of the dash, and temp gauge rising and falling. I'm thinking there is air in the system. It would seem I'm losing coolant somewhere but I can not see anything under the hood and it doesn't help that the coolant tank over flow has dumped some fluid too.

I have made it to a place I'm going to be at for the next few hours before I head home. I'm going to let the car cool down and then check levels again and also smell the exhaust for a sweet smell to try and determine if I'm having a head gasket problem or something else.

Anyone have any suggestions?

Thanks
 
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#3 ·
A few questions to start.

What kind of car, miles, check engine/ low coolant light ever come on, OEM coolant tank or aftermarket, last time the system was flushed, strange noise (what did it sound like), what does the oil (from the dipstick) and under the oil filler cap look like, coolant color in the coolant tank?????

Could be a few things but need a bit more info.
 
#4 ·
More info:

2004 VW Passat 4-motion, 1.8T, TIP, 220,000 miles. No white (or other) residue on dipstick or oil fill cap- oil level seems consistent. No sweet burning smell from the tail pipe. No check engine light, only temp light when temp started to rise. Aftermarket Valeo coolant tank, just checked- no visible cracks or leaks there. I've owned the car for the past 4 years and have only used G12 coolant. Currently putting a lot of water in it to limp it home.

I went back out to the car (it's been sitting for about an hour) and preformed a coolant bleed as suggested and described in the link above. I have started the car and took a very short drive and the coolant level remained at the proper level and heat works. But it was only a very short drive. I have a half hour trip home from here which I will do at 10pm tonight. I have also parked the car in a spot that was dry so I will check tonight before I leave to see if there are any wet spots under it.

I think I managed to take a short video of the noise when it happened earlier. I will see if I can upload it later after I confirm it's quality. Air in the system seems likely, but I can't seem to pinpoint where the coolant is going. Lets say the heater core has a leak, it should drain to the outside of the car correct? Floors inside the car are dry.

I will have to wait until tomorrow to do a more thorough investigation. I have spotted a hard coolant line to looks suspect but it's dry right now. I'll get a better look at it tomorrow.

Thanks for all the help tonight.
 
#8 ·
Large bladder? I didn't eat breakfast or lunch so....

Anyways, the story continues.

The car drove home fine last night. I stopped at the store to pick up some groceries and checked fluid levels, coolant was only down about a 1/4". Car sat in the parking lot for about 20 minutes and before I left I checked again, no change and no wet spots on the ground. Drove 5 block home and let the car sit overnight. Went out this morning and found the coolant tank very low. There are no wet spots under the car, wondering if the level of the coolant in the tank change because of the temperature difference. Then I noticed this:
Motor vehicle Wheel Auto part Automotive wheel system Tire


Which actually looked like this:
Auto part Wheel Automotive wheel system Vehicle Automotive tire


Could this be the real problem. If this o-ring wasn't sealed I would lose coolant, correct? Maybe the whole problem is just the cap? What do you think?
 
#10 ·
Well, you surely need a different cap so you have nothing to lose. Is the black lip in the bottom of the cap cracked? Can't really tell for sure but if the seal is not sealing it would be coming out your overflow nipple on the bottom of the tank as the coolant would flow past the cap.
TomK
 
#11 ·
Uh oh

I am experimenting with the cap, thinking that maybe the o-ring wasn't seated properly and that allowed some coolant to make it way out of the system.

But then something else happened this morning. When I first started the car it sputtered/missed for about 5 second then cleared up. A quick scan of the OBD showed a cylinder 3 misfire. Looks like I may have a blown head gasket after all. I don't see any white smoke from the tail pipe and the exhaust doesn't smell funny, but maybe that's because it's not really bad yet. I don't know.

This is really going to be a problem for me. I don't have a backup vehicle or a garage to work on my cars anymore. Might be time to buy a KIA.

Thanks for all the help guys.
 
#13 ·
Well, it is hopeful that the problem is just the cap. Until the new cap arrives in the mail I am using one off my Audi which seems to fit perfectly. It's been a day and a half and have had no coolant loss. I also did a compression test and found all cylinders between 125lbs and 140lbs. So I feel better about it not being a head gasket problem.

Thanks for all the help.
 
#15 ·
I'm going with the cap being the problem. The O-ring may seal enough for pressure to rise, then suddenly move and dump the pressure, resulting in immediate boiling of coolant in the head and loss from the reservoir. Cooling down reverses the pressure and might move the ring back to original position, ready to repeat.
 
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