Slowly losing coolant

[ephantmon]

I have an '03 KJ, 50k miles. Since I purchased it last year, I have noticed that I very slowly lose coolant in the reservoir. There's never a puddle under the jeep in the mornings. I never smell coolant when running the heat/AC. The oil is clean when I change it and when I pull the dipstick. The coolant in the reservoir is also clean. Based on what I've read, it doesn't seem like a busted head gasket, but what else are the possibilities? Thoughts/feelings/opinions welcome.

 

[2003KJ]

Any traces of coolant seeping out from the water pump gasket (or maybe the weep hole if there is one on our water pumps, can't remember). How about around the radiator hoses, thermostat, and radiator itself? It may be a big enough leak for you to start to loose some once it's warmed up and under pressure, but small enough that it's evaporating as soon as it's escaping.

I know you said you're not seeing it in the oil, but have you pulled the spark plugs to verify that it's not getting in the engine? You'd be able to tell if you saw a plug or plugs that were significantly cleaner than others, as coolant basically steam cleans them.

How much are you losing?

 

[ephantmon]

small amount lost

I don't know exact measurement, but I would say over the course of a month I lost maybe 5-6oz. I am changing the spark plugs later this week, I will check their cleanliness.

 

[JeepJeepster]

You would notice it in the exhaust if it was a head gasket.. Engine would probably throw a code too.

Check the radiator for cracks on the plastic sides.

 

[tjkj2002]

You would notice it in the exhaust if it was a head gasket.. Engine would probably throw a code too.

Sometimes yes and sometimes no.And the no OBDII codes will be thrown until it's to late.

 

[myjeepwalks]

Sometimes yes and sometimes no.And the no OBDII codes will be thrown until it's to late.

Correct.

Check to make sure the coolant isn't leaking into the crankcase oil. Headgaskets dont always leak externally.

 

[jnaut]

Yeah, at this point if you're losing coolant and there's no evidence of a leak, you're probably looking at an internal leak into the engine. Not good, not cheap. Good luck, let us know what you find.

 

[jnaut]

FYI, the last car I dealt with that had an internal coolant leak had compression problems. I'm not an expert wrench turner, but I don't know at what stage or how bad it has to be before you'll hear or feel compression problems without a full compression test.

 

[2003KJ]

FYI, the last car I dealt with that had an internal coolant leak had compression problems. I'm not an expert wrench turner, but I don't know at what stage or how bad it has to be before you'll hear or feel compression problems without a full compression test.

If it's a small enough leak it won't make it run bad or have compression problems.

 

[ephantmon]

Good news! I sent in a sample of oil to Blackstone labs at my last change. They found NO antifreeze in the oil (I had run conventional 5W30 for 2,000 miles). Molydenum was higher than average, 110 compared to a universal average of 77. They didn't comment on that, so I assume it's not a big deal. So wherever I'm losing coolant, it doesn't appear to be into the engine. Thanks for the various tips and advice on this issue!

 

[Marlon_JB2]

I believe Molybdenum is used as an oil additive.

 

[tjkj2002]

Good news! I sent in a sample of oil to Blackstone labs at my last change. They found NO antifreeze in the oil (I had run conventional 5W30 for 2,000 miles). Molydenum was higher than average, 110 compared to a universal average of 77. They didn't comment on that, so I assume it's not a big deal. So wherever I'm losing coolant, it doesn't appear to be into the engine. Thanks for the various tips and advice on this issue!

Your leaking coolant into the combustion chamber and it is being burned with the air/fuel mixture.Cracked head or leaking intake manifold.

 

[moparman]

Any traces of coolant seeping out from the water pump gasket (or maybe the weep hole if there is one on our water pumps, can't remember). How about around the radiator hoses, thermostat, and radiator itself? It may be a big enough leak for you to start to loose some once it's warmed up and under pressure, but small enough that it's evaporating as soon as it's escaping.

You are not going to find this without a pressure test unless everything is really clean and you can see the dried coolant spots. Look for screw type clamps and tighten them. Check your coolant tank for cracks. (Anywhere, not just the pressurized part.) tjkj2002's idea may be correct, too. That would be just as hard to detect. If you haven't had it pressure tested yet, what is taking you so long? lol

 

[ephantmon]

Warranty?

Your leaking coolant into the combustion chamber and it is being burned with the air/fuel mixture.Cracked head or leaking intake manifold.

If it is either of those things, what is the likelihood they will be covered by the 7/70 warranty I have on the powertrain?

 

[Marlon_JB2]

If it is either of those things, what is the likelihood they will be covered by the 7/70 warranty I have on the powertrain?

Highly likely?

And since you're under warranty, why didn't you just take it to the dealer in the first place?

 

[ephantmon]

Highly likely?

And since you're under warranty, why didn't you just take it to the dealer in the first place?

First, I have had some dealings with DC in the past and they have been less than great. Second, if it IS covered under the warranty, I wouldn't put it past them to try to cover up the true cause so they don't have to fix it for free. That's why I used an independent third party (Blackstone) to check for coolant in the oil. I brought it to the dealership two months ago, explained the problem, they said it was a faulty cap on my coolant reservoir and replaced the cap. It continued to slowly lose coolant, meaning that wasn't the only/real problem. I WILL take it back, but I'd like to get some other opinions/information on what it could be before simply blindly taking the dealership at their word.

 

[Marlon_JB2]

First, I have had some dealings with DC in the past and they have been less than great. Second, if it IS covered under the warranty, I wouldn't put it past them to try to cover up the true cause so they don't have to fix it for free. That's why I used an independent third party (Blackstone) to check for coolant in the oil. I brought it to the dealership two months ago, explained the problem, they said it was a faulty cap on my coolant reservoir and replaced the cap. It continued to slowly lose coolant, meaning that wasn't the only/real problem. I WILL take it back, but I'd like to get some other opinions/information on what it could be before simply blindly taking the dealership at their word.

You need a new dealership.

 

[sevenhelmet]

5-6 oz in a month is a very small amount of coolant. It it still possible that it's leaking out of the shaft seal on your water pump (there is a small weep hole on the bottom, very difficult to see.) I had a similar problem a few months ago, and didn't notice until it started to leak onto the serpentine belt, which threw coolant all over the front of my engine. I'd recommend checking around your water pump for anything suspicious.

 

[Lashlarue]

Binderdundat, for me it was a cracked block, no sign anywhere of coolant just losing a small amount on a continuous basis. Took the car in for routine service and mentioned it to service advisor, it was still under warranty, got a new engine and a reason to buy a new Cadillac.