Losing coolant, can’t figure it out

Hey Tacomaworld. I got an 05 v6 230k miles and I’m losing coolant at infrequent amounts. I have had it at different shops as it has been an on going issue. Things fixed include radiator cap, reservoir cap and drain plug, I had the block checked and it doesn’t have any compression issues and no evidence of exhaust in the coolant. I have also had various hoses replaced. I have had it pressure tested a few times too, even over night and no leaks are found! I have not replaced the water pump yet but I can’t even see a leak, I’m leaning toward just replacing it barring everything else. Any input?
Thanks

 

05 taco... hate to tell ya you described the classic headgasket leak on these years. Coolant gets burnt off in the exhaust and "disappears".

Pull spark plugs, ill bet one of them looks VERY clean compared to the others if they have been used for any length of time.

 

Thanks for your reply, I thought this as well but wouldn’t manifest with a radiator exhaust test? The oil has always looked normal, and there’s no smoke at all out of the tail pipe

 

not necessarily, gasket could be in a state where it lets water into the chamber on the intake stroke but seals back up on the other strokes.
a steam cleaned looking spark plug would support this
taking the plugs out and pressurizing the cooling system would test this condition

 

For sure, gunna pull them now see what I find

 

One looks slightly cleaner I guess

 

Hmmm none of those really are that level of steam cleaned I would think a plug that was in a cylinder that's burning water.

You might consider a cheap Amazon borescope that you hook to your phone / laptop and poke your head down into the cylinder to see how clean things are.

Are you positive the water pump isnt leaking?

 

That is really the only other thing it could be. I’m not sure if the pump is original or not but in the life I’ve had it and put about 100k on it, I have not changed the water pump. I don’t believe the previous owner did either and she was was very meticulous.

I travel for work and I’m currently on assignment. I’m just going to try to find a reputable shop to change in an OEM pump and see what happens after that.

safe to say I can keep driving it for a few days and just keep an eye on the coolant level no?

 

Yeah keep an eye on coolant level, check oil a time or two a week and call it good.

 

Thanks for all the help! Appreciated

 

Lots of good suggestions here. Just want to add that my v6 had mysterious coolant loss but no check engine light or running issues. My truck passed a block tester. I did pressure test my cooling system and did not notice any notable pressure loss. It was only till I used a borescope in conjunction with the cooling system under pressure that I could see an occasional drop of coolant run down the cylinder walls on both cylinders 4 and 6.

Also another note regarding the water pump, there were no signs of coolant leaking ever from my pump but after disassembly it was obvious that it had an active leak. The red crust was hidden by the pulley so it could not be seen by inspection. If you do not know the history of the water pump or when it was replaced, I think it is cheap insurance to have it replaced.

 

Thanks for the reply. I’m going to get the water pump done first as I’m on the road for work. I’ll do what you said next if for anything peace of mind

 

So i ended up having a pinhole in my radiator, borescoped all cylinders at the shop with no sign of head gasket leak. Happy for the news but also was kinda hoping to get the head gasket out of the way since it wasnt misfiring