2005 ls430 ultra... 145k miles. My coolant overflow tank looks empty after I added some coolant a month ago. I will refill with pink super-long-life premix to full once more and keep a close eye on it and bring to a pro if if loses it again, for pressure testing or whatever. Hope it is not a water pump ($$) after just 4 years/15k miles after replacing it, but also wondering if some other leak...

In reading about this, I read about coolant getting into and ruining transmissions due to a shared radiator design (same radiator for engine coolant, with transmission line running through).. Is a weak/deteriorating radiator at risk for this? Even if radiator seems ok, can the internal trans line crack due just to age? Would a new radiator prevent this?

The thing is, I have a feeling I have had a coolant leak (or a loss) for a while. I just replaced alternator as an emergency and mechanic said he saw some dried coolant but did not want to do anything. I checked and the reservoir (he didn't bother !!) and it looked empty.... will refill tomorrow, but it got me thinking.

I am looking for recommended course of action to prevent radiator failure and even more, trans failure from coolant infiltration. I imagine it is fairly pricey to replace radiator, but even is radiator is not leaking (say it is a bad clamp or (gulp) water pump), should I have radiator changed propactively on my 17 year old/150k mile car? What are the risks of failure leading to transmission contamination and failure?

I have seen related pages on the LS460 say to do this. https://www.clublexus.com/forums/ls-...ng-system.html...
"Recommendation: To avoid having this messy problem of transmission fluid mixing with coolant, replace your radiator if your LS460 is getting close to 100K miles, or install a dedicated transmission fluid cooling device, so that the transmission fluid doesn’t need to flow through the radiator. That’ll be a small cost compared with the cost and time to clean the strawberry milkshake mess."

Is a separate trans cooler viable, cost effective and smart, or overkill? Is changing the radiator enough, and a good idea, or can you tell if it is still "good"? Finally, is there an amount of coolant loss to consider acceptable if I keep topping up as needed (say 8 ounces a month)...

Thanks for reading and any replies.

 

Good chance that it is a leaking radiator. Do you see any dried pink residue on the top part of your radiator or any where around it? If you an do some fairly basic mechanical stuff you can replace the radiator yourself. There is a good thread on here on how to do it and I added some pics and info to that thread after I did mine. You can get a Denso radiator off of RockAuto for around $100. If I remember correctly I was quoted close to $1,200 for someone to do it. I was a little scared to do it mostly due to the potential loss for trans fluid during the swap but very little came out. I would also recommend keeping your OEM hoses and clamps is they aren't leaking, otherwise buy the OEM hoses which aren't cheap. I initially tried the cheaper Gates hoses and after a month or so the lower one started leaking and I had to go back to OEM hoses and haven't had an issue since.

 

Thanks, i will check tomorrow. . I did see some residue but thought perhaps that was from adding it last time/spilling, so I will clean it up when I refill and keep an eye on it. Appreciate the advice on the hoses. Are you talking about the main upper/lower radiator hoses? I am amazed frankly that I believe they have never been changed. Should I do them too? Never heard of a hose bursting in recent years, but they are 17 years old... used to read they rot from the inside out.

 

Check both hoses leading in and out of the reservoir. They will be old and brittle on a 17 year od car. Add this to the fact that coolant travels through the radiator to reservoir hose every time the car heat cycles. Toyota coolant crystallized when exposed to non-pressurized ambient air. Ambient air is present in both the aforementioned hoses which can potentially create a blockage. When this happens fluid takes the path of least resistance and exits the system usually at the small hose port just below the radiator cap or through the flimsy reservoir cap.

Both hoses (Genuine Toyota) are inexpensive to replace.
The reservoir should never be completely full even when hot.
The Full and Low marks on the reservoir can be ambiguous.
As long as there is some coolant in the reservoir, which is well below the low mark, you should be fine.

 

I have a new Denso radiator, thermostat, and hoses ready to install on my 06. Only has 96k on it now but in Texas, things take a beating during the summer.

I'll probably tackle it here this summer and it's worth it for the peace of mind.

 

ONLY a few sources will cause fluid to drain from reservoir. Worse to least issue 👇
1) valley plate gasket leaking.
2) head gasket blown3) water pump leaking4) thermostat stuck
5) radiator leaking6) water inlet/outlet house lose our leaking7) radiator reservoir cap broken not seating correctly 🤟🏽

 

Thanks sensei18 and others. Appreciate this reply to a relatively old post. Problem in not new for me and still not solved as I have not had occasion and time to bring car in to a mechanic. Playing with fire? Car never overheats, and I would know if it did based on when water pump did go bad 4 years ago and I saw engine start to get hot. in the gauge.. I am thinking bradland above might have it, as radiator when I check does show coolant. But I need a mechanic willing to diagnose/confirm. I have a second issue (Buzz/rattle in rear) and mechanic just said he could not hear it. It is intermittent but quite frequent. I've had some bad/cheating mechanics and other inept, so I tended to go to dealer. They told me it was heat shield but then added felt to it (at first they were going to just remove it but that did not seem right to me), but two days later the rattle was back. So I have not had great luck with non-clear issues. (When my alteranator died, that was obvious). A good, trusted mechanic is invaluable if you are not a fix-it-yourselfer. I am willing to pay for purely diagnostic time too, but the guy who replaced my alternator (at a general repair shop, Firestone, had to have car towed to an open place on a Sunday) mentioned coolant but was reluctant to go further. When I do bring it in, I will update this.

 

I have a feeling you're overthinking this. Check these 2 hoses (red) as they are both easy to access. Remove them completely, yes you will lose coolant out the bottom port of the reservoir. If both hoses are still pliable (unlikely) and you can move air through them (questionable) they are not the issue. Best practice o a 17 year old car is to simply replace them. There are also a number of small hoses in the cooling system that are also old and brittle. When this happens the seal is weak and can potentially leak. A small leak from one of these would go mostly unnoticed as it will evaporate from engine heat or just slowly trickle to the ground. Luckily coolant tends to crystallize when this happens so a thorough technician can easily find it.
Also, keep in mind the reservoir is not completely sealed like the rest of the cooling system so evaporation can and will happen...