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Discussion Starter #1
Symptoms:

Coolant disappears. no leaks on ground but looses about a gallong a month or more. I smell coolant when i get out of the car. This causes the car to reach temps of about 225 till i add more coolant but 195 to 205 seems to be the average that i get.

CEL saying the cats and o2 sensors are bad.

Bullydog tune is now uninstalled because of bad gas milage with it.

Bullydog meter says A/F ratio 1 is 12.6 at idle and normal opperating conditions. A/F ratio 2 which i dont know what it is but it stays constant at 8 and does not move. when i turn the CEL off it stays off for about a week.

I dotn appear to be losing oil. Cant smell or see it and when i drain it I get about 4.5qts out and put 5 in. this has been going on every 5k to 7k for a while.

Any suggestions on what to check next? If the cats are bad id like to just hollow them out... But if theyre going bad because im running to rich then that needs to be addresses with a real solution. The coolant worries me because i dont want it to be a head gasket... thermostat was replaced about 2k ago with a aftermarket part that opens 10 degrees lower than stock.
 

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Sounds like a HG to me.. Drain the oil and see if its sludged up like a milk shake..
X2... If fluid is disappearing at that rate with no leak odds are it's either going in the engine or the tranny. However when it mixes with engine oil usually there will be a white smoke out of the exhaust that comes with it.

But you said you have changed the oil since this has happened and it was in good shape?
 

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A head gasket won't necessarily leak coolant into the oil if it's bad.

There is a chemical that we use at the shop that pulls vapors from the cooling system to see if there are combustion gasses present in the cooling system. This is a sure way to see if there's one blown. Another way is to pull the spark plugs and inspect them. The cylinder with the leak will have a steam cleaned spark plug and will look noticeably different than the rest of them.

Make sure your radiator cap is stock for your truck too. Some folks use a higher relief pressure cap for whatever reasons and it can lead to head gasket issues.
 

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A head gasket won't necessarily leak coolant into the oil if it's bad.

There is a chemical that we use at the shop that pulls vapors from the cooling system to see if there are combustion gasses present in the cooling system. This is a sure way to see if there's one blown. Another way is to pull the spark plugs and inspect them. The cylinder with the leak will have a steam cleaned spark plug and will look noticeably different than the rest of them.

Make sure your radiator cap is stock for your truck too. Some folks use a higher relief pressure cap for whatever reasons and it can lead to head gasket issues.

It doesnt always leak into the oil... but a gallon per month is major. If it were dumping that much into the cylinders the engine would run horrible and in extreme cases possibly hydrolock. Also, the easiest way for a novice to test is with a leakdown test.
 

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Discussion Starter #8
Buddy at work says pressurize the coolant. Let it sit for a while. Pull the plugs and crank the engine. It may be half a gallon. I plan to refill it today since it's getting hot and then I'll have a better idea about how much. I'll be checking the oil and trans fluid too.


Sent from AutoGuide.com Free App
 

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Discussion Starter #12 (Edited)
Heres the oil and transmission fluid. I added a little more than half of a gallon of coolant.

exhaust looks fine but it has a putter to it. make sense? bullydog tune is off. no change in gas milage but it was just a 4 mile trip home from work. whats the next step?

EDIT: coolant tank was full when i filled it. i let the engine cool and it was between the cold and hot line.

i checked under the oil fill cap to see a milky color and it was clean oil again.
no white smoke from exhaust under idle and 3k rpm.



 

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If not leaking or getting in oil, it's burning it, like Cyclemut said - and that is very common way for HG to fail - and maybe what damaged cats.
 

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Did you check the a/f with the motor warm or right after a cold start? 12.6 is believable for cold start but it should be 14.5-15 for a hot idle. If your running that ratio when warm then something is off. Losing that much coolant points to it likely going out the exhaust, unless your radiator cap is bad, but it's still a lot. You can do the dye test to see if you have exhaust in your coolant too. I have an 03 Toyota highlander in pieces in my garage because the threads in the block stretched and it started pushing exhaust into the coolant and overflowing it. Coolant was also leaking at the head gasket by dripping onto the exhaust so there was never a puddle.
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Discussion Starter #16
A/F stays the same hot or cold...

I did however find this!

This is either a good sign or a bad sign. I wasnt able to look any further than this so Im not sure if this is the source or if its higher up. Any ideas where it could be coming from? I dont know where the coolant actually runs to.

This is looking through the front of the engine by the driver side. steering rack at the bottom fan to the left of the pic.
 

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I'll gander a guess. I'm going with a failing water pump. The only reason I say this is I was leaking coolant on my 96 pathfinder a while back. Turns out they have a built in weep hole and that's the telltale sign. I'm going to guess the xterra has a similar weep hole.

I kept good maintenance on the pathy, so I noticed it quick. Only the drip, everything else was good and performance was fine.
 

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If you can smell the coolant, it is an external leak. Just isn't big enough to be running down on the ground. You can pretty much rule out all the panic about major repairs. Just follow the coolant up to the leak.
 

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Yep, that looks like the water pump to me as well. Starts as a slow to medium leak, then when it goes, it GOES - meaning any coolant you put in will pour right out the bottom.

If you're doing the pump, go ahead and do the timing chain at the same time - just getting the pump off, you're halfway to getting the timing chain done.
 
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