Another coolant loss thread. Advice needed...

[zguy1]

#6 looks fine. Id be concerned about #4. I havent seen a plug that bad in any toyota I have owned. Thats way too much carbon. I would seafoam the top end and add 1qt MMO to the oil on the next oil change to clean the piston rings. Change your pcv valve. It might be sucking in too much oil

Did you use a vacuum port to draw vapors from the radiator or the squeeze bulb? I was worried about mine when I bought. I ran a vacuum line from the intake to the device and bubbled it for 5 minutes. Still no change to the fluid color. If it didnt change color then you need to keep looking for the leak.

Re-gap the plugs

I was supposed to leave on my road trip today but wanted to check a few things before I headed out with the truck. The pcv was changed in 2020 or about 36k miles ago. I only have 3100 miles on the current oil and was planning on changing it before going as I will be putting about 2500 to 3000 miles on it during my road trip. I have never used seafoam or MMO. I guess I could try both.

With regard to the combustion tester, I removed the radiator cap and warmed up the truck. I kept the coolant below the neck by about 2" or so by siphoning it out while it was warming up. I put the tester on top of the radiator and used the squeeze bulb. It was an imprecise test as the test tool does not seal around the sides so I tried to keep it flush along the bottom edge.

It looks like I am still going to take the truck, albeit I am a bit nervous. I am willing to try a few more things tomorrow so I could leave Tuesday AM.

 

[zguy1]

#6 piston crown and spark plug look suspiciously clean, usually caused by coolant ingestion. Steam is an excellent carbon remover.

My next diagnostic step would be renting a cooling system pressure test kit from Autozone/Advance Auto and pumping it up to the cap's rated pressure. A head gasket will drop pressure slowly and steadily as soon as you stop pumping.

Are you having any rough engine idle on cold startup and/or hearing gurgling/waterfall noises from the dash (heater core)? These are often reliable indicators of head gasket failure when combined with coolant loss.

I can rent a cooling tester tomorrow and give that a try.

I was thinking about changing the radiator cap but not if that is warranted. I never replaced it before even when I changed the radiator in 2020.

I do not hear any noises from the dash. The car runs great and has never set the check engine light as long as I have owned it.

 

[Drcoffee]

When the head gasket fails, it allows pressurize gasses into the cooling system. This forces coolant into the resevoir and it overflows to the ground. What you would see is an empty resevior which it does not seem to be the case.

The head gasket could be leaking beteen the head and block. You would see crusty pink somewhere on the engine.

Otherwise its leaking from a hose or maybe the heater core.

This is how mine looked at 220,000 (orig plugs). Some are cleaner than others. Notice the gap sizes, and it still ran pretty good.

Lastly, yours is a 2008 which means its beyond the timeframe where the head gasket failures were typically seen. Id take the trip and not worry about it.

 

[Drcoffee]

Where you see the pink crust by the t-stat is an odd place to have it. Thats the oil filter housing. There are some small hoses below the thermostat housing that could be the source of you leak. You will see them once you do the water pump.

 

[OopsIBrokeIt]

I just went through similar in the last couple weeks. I first spotted some crusties up near the throttle body and thermostat, but was unable to identify any leaks.

A few days later I noticed a semi regular drip of coolant under the car at idle and went looking, it was the water pump leaking and the serpentine belt flinging coolant around the bay from there.

I went ahead and replaced pretty much all the hoses just as insurance, but most were still in decent shape for being original.

 

[zguy1]

When the head gasket fails, it allows pressurize gasses into the cooling system. This forces coolant into the resevoir and it overflows to the ground. What you would see is an empty resevior which it does not seem to be the case.

The head gasket could be leaking beteen the head and block. You would see crusty pink somewhere on the engine.

Otherwise its leaking from a hose or maybe the heater core.

This is how mine looked at 220,000 (orig plugs). Some are cleaner than others. Notice the gap sizes, and it still ran pretty good.

Lastly, yours is a 2008 which means its beyond the timeframe where the head gasket failures were typically seen. Id take the trip and not worry about it.

I'm planning to take the trip at this point. I may pick up a new set of plugs from the dealer even though these are relatively "new" compared to the ones I took out when I bought the truck. Yesterday, when I was using the combustion tester and was finishing up, I revved the truck with the radiator cap off and coolant came out. I assume that was from the water pump pushing coolant through the system as opposed to exhaust gases escaping.

Where you see the pink crust by the t-stat is an odd place to have it. Thats the oil filter housing. There are some small hoses below the thermostat hosing that could be the source of you leak. You will see them once you do the water pump.

Right, I will hopefully know more then I remove the water pump and thermostat when I get back.

 

[zguy1]

I just went through similar in the last couple weeks. I first spotted some crusties up near the throttle body and thermostat, but was unable to identify any leaks.

A few days later I noticed a semi regular drip of coolant under the car at idle and went looking, it was the water pump leaking and the serpentine belt flinging coolant around the bay from there.

I went ahead and replaced pretty much all the hoses just as insurance, but most were still in decent shape for being original.

Aside from that tiny bit of crust, everything is bone dry that I can see. Maybe more will be revealed when I do the water pump eventually.

 

[OopsIBrokeIt]

Do you see any stains or water marks on the serpentine belt? That was part of how I identified the WP as the probable source of my leak.

 

[zguy1]

Leak found and it's not good news...

Well, I was able to get another inspection camera with the ability to see from the side. I also rented a cooling system pressure tester. I pumped up the system to 13 psi. I could not see any leaks and the pressure held steady.

I went ahead and pulled the spark plug from cylinder #6 and started looking around at the gasket area in the cylinder with the camera. I saw an area that looked questionable and a bit wet. I proceeded to wait and after about 5 mins I saw a single droplet form from the head gasket area and roll down the cylinder wall. The drop appears every 5 or 10 mins but that is under 15 psi.

I know I have been driving like this for sometime but I can't knowingly take this truck on a road trip with a fully of gear with the risk of breaking down. Most shops can't fix it and dealers will charge a fortune. I also don't know what else is wrong. Could the head be warped? It never overheated while I owned it but that is too much to risk on the road.

2008 V6 4Runner with 295,221 miles. :rip:

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[Seymore Butts]

Thanks. I can't wait for Rock Auto parts so I was able to find a Toyota water pump and ASIN thermostat at Amazon that I could get in 1 day. The Toyota water pump is about $25 cheaper than my local Toyota dealer.

Any recommendation on brand and parts for pulleys?

Why? Are any of those parts leaking your coolant?

 

[zguy1]

Why? Are any of those parts leaking your coolant?

No, those are part of the drive belt system.

 

[Bluesky 07]

No, those are part of the drive belt system.

Can't speak for the guy but my take was that he's yanking your chain.

 

[zguy1]

Can't speak for the guy but my take was that he's yanking your chain.

I figured that. My normal go to is to be a wise ass but I figured I would tone it down. Don’t know how sensitive this group is.