Coolant Leaking Into Transmission

[afinley]

Hello all. I'm hoping someone can lend their $0.02 to this issue I'm having with my '00 RX300 2WD (~175k).

I've noticed lately that my coolant reservoir has been draining all the way to empty after I fill it up and drive it for a week or two. After getting under the car last night and looking for leaks with no luck, I decided to check the transmission fluid level because the engine oil looked good (no indication of coolant in the oil). Lo and behold, the transmission fluid level was about an inch above the maximum hot line even though the car had been sitting for about 4 hours.

The tranny fluid is more of an orange color than the standard pink/red but I cannot tell if that is from age or mixture. I seem to remember seeing some bubbles in the transmission fluid the last time I checked it too. It also doesn't help that both fluids have similar colors (thanks Lexus).

This leads me to think that the transmission cooler line inside the radiator has cracked and coolant is being forced into the transmission system when under pressure.

1. Can anyone think of a good way to isolate this issue to determine if this is really the problem? I'm thinking I can bypass the cooler line in the radiator, warm up the car, and see if coolant starts steaming out of the open cooler line.

2. Is there a way to replace the radiator without discharging the AC system and pulling out the condensor core?

3. I'm guessing I need to match the radiator size to my VIN? It looks like there are two different sizes on Rockauto (16mm vs 27mm thick core).

I'm driving my '73 Deville in the meantime so I don't do anymore damage to the transmission - if I have done any damage. I haven't noticed any problems with shifting or any weird noises so I think it might be ok as long as I get the coolant out and fix the leak.

Thanks for any help y'all can provide.

[afinley]

Update: You should always admit when you messed up. I'm a dipstick. I was checking the transmission fluid with the car off. I don't know why I forgot that.

Good news is, I don't have to worry about the transmission as the levels are good. Bad news is, I might have a coolant leak. I'm going to check the radiator cap and see if it could be that.

[lenore]

I suspect bad radiator...by the way the Rock auto Denso radiators are great...at least on my RX400h.... by the way another place the fluid can leak is between the intake manifold and cylinder head. I had this crust by the thermostat housing on the RX300 and it turned out to be a bad intake manifold gasket which also has radiator fluid going thru it.

[afinley]

So it looks like the coolant is leaking from either the intake or the coolant gallery plate on the top of the engine block. I can just barely see a red pool under the intake and if I stick a stick down there it comes back with the tip red and wet. Six months ago I redid the knock sensors and wiring harness and while I was in there, I discovered that coolant had leaked under the gallery plate so I pulled it off, cleaned and resealed it.

I starting to think it's a bad intake manifold gasket. Looks like I get to dive back down in there. I'm going to replace the IACV hose clamps while I'm down there as well, just to make sure.

[sadclown]

I have an impression that the issue is caused by a radiator leak.

[afinley]

Well I got down to the gallery plate and discovered that I had forgotten to unlock one of the hose clamps when I was putting everything back together after replacing the knock sensors. Stupid mistake that cost me extra time but I'm glad I found it. I released the lock on the hose clamp, put everything back together, and haven't lost any coolant in the past two weeks.

Moral of the story: always double check your hose clamps

[VBdenny]

Don't "stupid" yourself because YOU actually fixed it yourself. Oh how many times I've had to redo things over due to missing a step along the way. Stupid is people who give up and never try. Nice to have you here.

Denny