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Discussion Starter #1
Hi all,

I have been experiencing significant coolant loss with no visible leaks. Been through several threads and the closest I found that resembles my situation is the following: http://www.rav4world.com/forums/99-4-3-mechanical/88513-coolant-loss.html

My car is a 2009 Rav4 V6. Where the h*** does all the coolant go?? I have had to top up every 3-5 days depending on how I long I drive but still no leaks or suspicious exhaust fumes. I haven't checked the oil consistency yet but I will do that asap.
A friend of mine suggested I use a product such as K Seal to plug the "invisible" leak but I am averse to pouring something that might go into the engine if the leak is internal. (anyone who has experience with such products?)

If a leak can still not be found but is there due to the amount of coolant I keep putting in, what should I change to make sure there's no more leak? Water pump? Head Gasket?

Many thanx in advance for any ideas.
 

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By all means check the condition of the oil immediately.
 

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How are you measuring the loss? What do you mean by "topping it off"? If you fill the reservoir to the top up normal expansion as the engine warms up will push the excess out the nipple behind the cap.

Except for your link I can't recall ever hearing of a V6 losing coolant and in fact your post got me to check mine which I've never done in the almost 4 years of ownership! :doh: And I have no idea where the level was then. It is about the distance between the FULL and LOW marks below the LOW mark. Guess if I had some of the pink stuff I'd add a little but IMO as long as the reservoir isn't dry there are no worries.
 

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It could be a head gasket leak or the water pump. Another slim possibility is a hose leaking. You may need a mechanic to help find the problem. In any case let us know how this goes.
 

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I have not had any coolant loss with my '11 V6 and now the year is '16. Always is at the Low mark when cold, when the coolant level should be checked. Adding coolant at that point will simply result in at least most of the added amount being blown out of the system, as Dr. Dyno notes.
 

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Oh, yes, the infamous mystery coolant leak.

These can always be fun. I have found that sometimes the leak only occurs when the car is at operating temperature and the coolant is leaking out onto some part of the hot engine and almost instantly evaporating--in effect disappearing!

But I assume that you have crawled around and looked under the car with a flashlight while the car is idling at operating temp and looked for drips? Dried coolant stains can be a clue. Make sure you have driven the car for a while before doing this so that the car is at max temp.

Of course the alternative is a blown head gasket. If you can't find any possible source of a leak, you should get it checked out to see if it has a blown head gasket. If you are getting a lot of coolant in your oil it can cause engine damage. So don't wait too long to check this out.
 

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The factory coolant in the RAV4 is red, so coolant leaks look like pink cotton candy. When I overfilled mine, it leaked out the overflow tube on the reservoir, leaving a pink crust that was easy to spot.
 

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Discussion Starter #8
Oh, yes, the infamous mystery coolant leak.

These can always be fun. I have found that sometimes the leak only occurs when the car is at operating temperature and the coolant is leaking out onto some part of the hot engine and almost instantly evaporating--in effect disappearing!

But I assume that you have crawled around and looked under the car with a flashlight while the car is idling at operating temp and looked for drips? Dried coolant stains can be a clue. Make sure you have driven the car for a while before doing this so that the car is at max temp.

Of course the alternative is a blown head gasket. If you can't find any possible source of a leak, you should get it checked out to see if it has a blown head gasket. If you are getting a lot of coolant in your oil it can cause engine damage. So don't wait too long to check this out.
Thank you every one for your thoughts.

I measure the loss a few days after I have added coolant to full level. I drops to below Low indicator after 3 days more or less and then if I continue driving (without adding) it drops again to the point where its no longer visible in the coolant reservoir and thats when I add more. Then the cycle repeats.

I have checked the oil consistency and I dont think coolant was added. Really not sure how its suppose to look like. Also, there's no creamy deposit on the oil filler/cap which from my research is also another way to determine if coolant was added to the oil. How would it look if that was the case? white-ish? Any other to determine leaky head gasket?

I have indeed looked for leaks under the car to no vail. Damn it such quantities must go somewhere???!!!

Gonna have the head gasket and water pump checked by a mechanic on monday. Anything else I should look for? what about the hose? If it had been leaky, it would be visible no?
 

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Of course a V6 has two head gaskets, one for each bank of three cylinders. When a HG starts to fail coolant leaks into the cylinder from the water jacket primarily after the engine is shut off and there's still pressure in the radiator.

I'm working on a friend's Civic where either the HG is failing or the cylinder head is cracked. Another friend who's a professional mechanic and owns a shop diagnosed the issue by looking into each cylinder with a bore scope and finding piston #3 wet after the car sat overnight. So each morning a small amount of coolant is lost when the engine is started. I haven't checked the oil yet since I just got the car but oil contaminated with coolant becomes a lighter than normal coffee color not the normal darker color it gets with use.

Unlike your 2009 RAV4 the Civic is a 2003 with nearly 200K miles and it isn't worth spending an estimated $1500 on repairs so I'm going the try some liquid block sealer as a cheap last resort. It might work or not but could save her buying another car immediately.
 

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Discussion Starter #10
Of course a V6 has two head gaskets, one for each bank of three cylinders. When a HG starts to fail coolant leaks into the cylinder from the water jacket primarily after the engine is shut off and there's still pressure in the radiator.

I'm working on a friend's Civic where either the HG is failing or the cylinder head is cracked. Another friend who's a professional mechanic and owns a shop diagnosed the issue by looking into each cylinder with a bore scope and finding piston #3 wet after the car sat overnight. So each morning a small amount of coolant is lost when the engine is started. I haven't checked the oil yet since I just got the car but oil contaminated with coolant becomes a lighter than normal coffee color not the normal darker color it gets with use.

Unlike your 2009 RAV4 the Civic is a 2003 with nearly 200K miles and it isn't worth spending an estimated $1500 on repairs so I'm going the try some liquid block sealer as a cheap last resort. It might work or not but could save her buying another car immediately.
Here it would cost almost double that. They dont have the part here so they have to order it so cost plus shipping plus actual time spent doing the work would be too much for me. Although the car is not displaying any of the common symptoms of head gasket failure, thats the only thing that makes sense in terms of where the coolant goes. Last wednesday I added a litre and by the next tuesday, I had to refill. So am going to go with a head gasket sealer like Blue devil, drain the oil and replace it and hope for the best.
 

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I used AlumAseal on the Civic and it seems to be working. Another week or so will tell.
It's made to seal radiator leaks but I like the idea of using an aluminum powder on aluminum cylinder heads. And unlike the can of Block Sealer I have it doesn't require flushing the coolant out of the system. I did squeeze the heater hose with vise grips for a couple days after I added the sealer to keep it out of the heater core.
 
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