Very slow highlander coolant leak

2008 Highlander - super slow coolant leak. Dealer can’t find it via pressure test. Never trips sensor, but after 6 months or so, the heater doesn’t work well unless turning to the left. Ideas? Has happened since new, but now Just out of warranty. Dealer has recorded two pressure tests and leak, but I’m wondering what to do.

Go to an independent shop specializing in cooling system repairs. They deal with older cars more than dealers do and are aware of all the possible places a car can leak.

Anyone can do a pressure test, but finding the cause of the leak is something else.

Docnick - Thanks for the advice. Just a weird situation to have a problem which the dealer acknowledges, but doesn’t seem to know how to fix.

do you ever see coolant on the ground? After 6 months is there no heat due to coolant level? If so when you fill it do you bleed the system?

No, no coolant on the ground and no smell. Yes, after 6 months the coolant level falls just enough so that the heat is intermittent. Dealer has topped off and bled the system each time, which fixes the heating problem. Seems like just a super slow leak. Wondering what the best way to find a leak is?

If it is the 4 cylinder look for stripped head bolts. Look behind the cylinder head for coolant markings-just google it and you will see.

The dealer cannot find the leak, but I would think be responsible for the leak. If it were my car I would try another dealer, given that they will do it under warranty. Otherwise find a good independent mechanic to find the problem, then get the dealer to fix it and hopefully reimburse you for the analysis.

so is the reservoir completely empty every time you lose heat? I used to be a toyota technician for a couple years and worked at a toyota dealership. After 6 months it is not uncommon to use coolant. Every car that came in we would always top off coolant when needed, which was almost every vehicle. But to completely go through the entire reservoir tank and also lower the coolant level enough to cause no heat is another thing. Have you checked your reservoir tank when having no heat? For a leak that small…a pressure check would be almost impossible to tell where the leak is coming from. Pressure testing is for bigger leaks. How well do you know parts of the engine? there are only so many spots it can be leaking from…So I would start with visual inspections yourself, even if the dealer claims they couldnt find a leak. The new 6 cylinders have really bad water pumps. I have replaced many water pumps with less then 30,000 miles on them. That is always the first thing I checked on all newer toyotas with more then 20k miles during inspections. Because they are always bad. I remember one day I replaced 6 water pumps on the 4 cylinder motors in one day. So that would be the first thing I would look at. The 6 cylinders are tricky to look at due to little clearance between the pump and the body. But the newer 6 cylinder has a timing chain so the pump is on the outside of the block and not under any timing covers or anything. You will need an extendable inspection mirror and a flash light. Find the water pump and put the mirror underneath it. Get the flashlight down in there so it lights up the underside of the pump. Toyota coolant is pink so if there is pink on the bottom side of the pump you will see pink residue.

Then just check all coolant hose connections…anywhere you see pink residue it means there is a coolant leak there. How many miles does the highlander have on it and have you had the water pump replaced anytime in the life of the vehicle?

Thanks for the ideas. I’ll give it a good inspection and let you know. Do you think there is risk of long-term damage to the engine. Just have this fear that coolant might be getting into a cylinder or something and will cause a problem down the road.

Btw - it is a 2008 V6 with about 54,000 miles

For a super slow leak like that, there is not much danger, except if you don’t keep an eye on the coolant level and let it run too low. Running it so low the heater doesn’t work as well is too low IMHO. This means that the coolant reservoir is empty, and the coolant level needed for the engine is running down. It seems like a very mild seepage and can easily be managed by just checking the level every now and then.

If I were you, I’d open the hood once a month at the very least before starting the truck and check the coolant level in the translucent reservoir. It has lines on it to tell you when it is full and low. The owner’s manual can tell you exactly which reservoir is coolant.Always add some coolant to keep the fluid level between these lines, and do not overfill. The empty space above the full line is for expansion when the coolant gets hot.

I’m kind of reluctant to mention this,but there are some products available to stop coolant leaks inside of engines. I’m reluctant because these leak stoppers can block up coolant passages and make a mild problem like yours a major problem.

I had a very light coolant deposit on the top of my radiator and I added a tablespoon of coarse pepper to the radiator and the leak stopped.

Busted knuckles is right the slow coolant leak wont hurt your engine as long as you keep an eye on it. And yes waiting until the coolant level is low enough to effect your heating would be too far for my liking. One thing bustedknuckles also said was about the use of coolant additives. DO NOT USE STOP LEAK!!! Especially in a 2008 with only 54,000 miles on it…Use the stop leak in your 95 chevy cavalier so when you ruin the motor they are a dime a dozen…Do not take the risk of ruining a good solid pretty new motor. Yes stop leak will stop coolant leaks…and it will also stop coolant flow!!! If you have any kind of extended warranty…say good bye to it if you dump stop leak in your cooling system.

Thanks to everyone for the great comments. My goal is to find the leak and get it fixed under warranty. I’ll let you know how it pans out.