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Discussion Starter · #1 ·
Firstly, the car is beautiful. I'd post pics, but I'm too pissed right now. :facepalm: Car is a 2000 BTW.

When I got the car, I did all the regular maintenance, engine oil, tranny, and coolant. The coolant level was down in the overflow when I got the car but I didn't think anything of it because the car has only 35,000 miles so I figured, hey can't be anything serious. But when bleeding the air from the cooling system, I kept getting bubbles in my Lisle funnel no matter how long I did the process. Now I've had engines where it took a very long time to get all the air out. But on this car, even with many repeated attempts, I still see bubbles. So to break it down, here are my symptoms:

  • Bubbles in rad, especially when revving the engine. Sometimes there are a few large ones, other times tiny ones. But it's consistent, I can always get the bubbles to show by revving up and down. No amount of time trying to get the air out ever accomplishes anything, air keeps bubbling up.
  • Overflow tank changes level, it goes up about an inch when the car is warm, then goes back down when cool. I've added coolant to the top line, but after driving for a bit and the car cools, it drops, sometimes up to an inch below the top line.
  • I have no visible leaks, smell no coolant, and don't see white smoke as far as I can tell. But it's been cool here to it makes it difficult.
  • I put my funnel on the car when cold, ran it, and watched as the coolant level rose and filled the funnel up about 2 inches. Again I saw bubbles off and on. Also, the overflow tank also filled up with coolant, I have never had that happen before. Maybe just a fluke or my funnel is not sealing onto the inlet properly?
  • Frustrated, I had the car block tested by a rad shop. It took them what seemed like a long time (like they were not sure what they were doing) but the test fluid changed from blue to green, eventually. The tech said it took "a really long time" for the fluid to change. When I asked how long, he didn't give me a definite but it was maybe 10-15 minutes. Would have liked a straight answer.

So my question if for people that have a 1MZ-FE engine, do you see coolant level changes in the reservoir? Up when hot, down when cold. All the cars I have owned, I have never seen this unless there was a cooling system problem. According to the owners manual the level change is expected, perhaps it is for this engine?

The block test, is it possible there was a false positive? There were other cars around it running, not sure if that could contaminate the liquid after awhile? How can I be absolute certain where my coolant is going? I can do a compression test on the front bank, but the rear bank seems impossible to access. I've read that a great way to test for a coolant/HG problem is to pull all the plugs, pressurize the cooling system for an hour or more, then crank the engine with all the plugs removed. If there is a leak, coolant will spit out the spark plug holes. Has anyone ever done this?

Looking for any advise, right now I feel like driving the car through a wall, I paid good money for this car because of the low mileage and expected only minor problems at best, but I have a bad feeling I'm looking at a bad engine. :ugh3:
 

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You sound much more experienced than I with cooling system issues, but FWIW, if your coolant levels when the engine is hot and cold correspond to the coolant resevoir tank marks, and there is no appreciable white exhaust 'smoke', and the overall coolant level stays fairly consistent, I'd look for something else other than a head gasket, especially if there is no direct evidence of overheating.
 

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Discussion Starter · #3 ·
The coolant level does drop over time, and I see no signs of leaking. The only other thing I could look at is the water pump, it might be slowly leaking out the seal, but I would still expect to see coolant on the ground. But the two things that make me think head gasket are the block test, and the bubbling.

Does anyone have experience with dye kits? Are they of any value to find a leak? I may have to end up removing at least part of the intake and pull all the plugs and do a pressure test. I'm tempted to take the car to Lexus, but I'm sure I'll be raped on price.
 

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Discussion Starter · #4 ·
Just to update for anyone that cares, I found the problem. The drain petcock on the back side of the engine was leaking. Coolant would never show on the floor, because it happens to be directly above the exhaust pipe, so whatever leaked was quickly burned away. I found the problem when I was inspecting everything for leaks, I saw a small pinkish stream coming from that area (I used Toyota super long life, which is pink).

The reason it was leaking is because the threads were stripped in the drain bolt, and also in the aluminum cover/plate that is bolted to the block. For some reason, Toyota used the identical type of material for both threads, a big no no. Both are the exact same type of aluminum. Most of the time in my experience, Toyota uses a softer material for the removable part, and a more durable, harder material for whatever part is more permanent. Not this time, so the two metals fused together and stripped. :facepalm:

When I initially did the coolant drain and fill, the bolt did feel a little "soft" when tightening, so I did not apply much torque on it and figured it was just that way, maybe a rubber gasket or something that gets squished. But it was stripped and was not threading in all the way, allowing coolant to leak past the little O ring which is at the end of the bolt.

I got lucky and found a 1996 1MZ at the wreckers which had the same bolt. But restoring the threads on the block plate was tricky. I had no tap that matches, it's a strange size. But as luck would have it, the oil pan drain plug is identical (I found this out by experimenting when I was at the wreckers). So I ground down the end of drain plug I got at the yard, and used that to carefully restore the threads. I put anti-seize on the bolt, not gonna let that sucker get stripped out again.

Disappointed in Toyota on this one, poor engineering. But no more coolant level dropping on me. :)

BTW, the rad shop that did the block test don't know what they are doing obviously. There are no combustion gases in my coolant.
 

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I don't know why, but it seems normal to go for the worst case scenario first and look for the simple stuff later. I once spent hours working on a Mercedes engine, convinced that one of the hydraulic lifters or a cam lobe was shot, only to find out one of the lifters needed to be tightened to hold oil pressure, a previous mechanics mistake of course. Or, recently, hours spent fiddling with the Lexus IAC valve, when the TPS was off (or at least I think that was it) or the ECM needed a few driving cycles to reset itself (I think...but I did fear for the worse at times). A dealer could have sold me any number of $$$ parts if I didn't know better to trust myself first.
Anyway, :chug: for the analysis, finding the problem, and fixing Toyotas mistake...without breaking the bank.:thumbsup:
 

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Discussion Starter · #6 ·
I don't know why, but it seems normal to go for the worst case scenario first and look for the simple stuff later.
So very true. Even when I tell myself, look for the simple explanation first.
Anyway, :chug: for the analysis, finding the problem, and fixing Toyotas mistake...without breaking the bank.:thumbsup:
Yep didn't cost me anything, the Pick 'n Pull just lets me walk out the door when I show them a handful of bolts. I actually have a feeling the Lexus dealer originally damaged the drain plug, because according to the service history, they did replace the coolant in 2006. When I loosened the bolt, it just felt "off". Still miffed why Toyota would use an aluminum bolt, dumb.

Anyway, I'll post some pics when I get a chance, I absolutely love this car it's a keeper.
 

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Discussion Starter · #7 ·
Some pics. Notice the coolant reservoir is over filled, but it stays that way, previously I could never keep it above the top line.

 
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