I have a 2005 Lexus GS470 with 100K miles. There are various Lexus forums that recommend replacing the radiator of older vehicles as preventative maintenance even if there are no leaks since there is a chance of transmission fluid leakage from the cooler in the radiator. Apparently if the transmission fluid leaks in the radiator it will cause significant damage. However, my Toyota dealer said this wasn't necessary.
Do you recommend replacing the radiator of older vehicles even if there are no signs of leakage, and if so, do you believe a radiator purchased from the dealership is required or is the OE manufacturer (Denso) adequate?
Thanks for all of your content in this forum and on YouTube.
@tchid
If replacing parts for preventive maintenance maybe just replace cars since you might miss a part that will destroy the car. ....... If it ain't broke, don't fix it.
In my opinion, the radiator should be replaced when coolant temperatures begin to exceed the normal temperature range. This means that the radiator is gunked up inside and is not properly cooling the coolant anymore. Of course, you would also replace it when it starts to leak. Basically, replace the radiator before it causes your car to overheat from not cooling properly. Some people do it as preventative maintenance, and some do it when their engine starts to run hotter (but this could also mean a bad thermostat or just old coolant).
You can replace with an OEM radiator from dealer or OEM quality like Denso.
Nope. I’ve never replaced a radiator.
Thanks for your response but my main question is whether it should be replaced as a preventative measure to ensure there is no transmission fluid leakage from the transmission fluid cooler inside the radiator.
@tchid
NO!
@tchid
There is no such thing as a separate radiator inside of a radiator. The only fluid that is inside the radiator is coolant, nothing else. Your vehicle has a separate transmission cooler (air to fluid or coolant to fluid), probably mounted right on top of the radiator. If you see any transmission fluid leaks around it, THEN you replace the transmission fluid cooler, not the radiator.
@razmigb
There is a such thing. I don't know about Lexus, but radiators will sometimes contain a liquid-to-liquid heat exchanger for transmission fluid.
Anyway, radiators are not an preventive maintenance item.
@mountainmanjoe
Oh wow, someone told me about those one time but I never believed it lol. I'm sure they're outdated though. Most cars now have their separate liquid-coolers or air-coolers for the oil and/or transmission fluid.
@razmigb
no... not outdated. Liquid is a much more efficient carrier of heat than air. That's why we drive liquid cooled engines instead of air cooled.
My radiator does have a transmission fluid cooler inside the radiator. Apparently there have been instances when the coolant leaked into the transmission fluid and caused major transmission issues that could easily require a new transmission. I was hoping Scotty was familiar with this issue and couple comment if this is a rare occurrence or if this is something he has seen many times. Regardless, it seems like it is a poor design.
@tchid
rare
@tchid
Yes it is a poor design, which is probably why I haven't come across any. Putting a cooler WITH fluid inside another cooler WITH fluid is not a good idea; it's just asking for trouble. Why risk the chance of mixing fluids together? I bet Scotty thinks its a stupid design too. But if you don't feel comfortable with it you can replace it; it's your choice at the end of the day. I've seen people retrofit a separate transmission fluid cooler and "plug up" the integrated one on the radiator.
@razmigb
I've never had an issue with it. It can be engineered so there's virtually no chance of mixing. You have three difference fluids going into an engine right? It's a good design because it removes heat more efficiently than liquid-to-air coolers.
@mountainmanjoe
You can have liquid-to-fluid cooling without integration inside the radiator. I'm saying the idea of having the cooler inside the radiator "surrounded" by coolant is a bad idea. We have liquid-to-fluid coolers that are separate from the radiator itself where dedicated coolant lines run from the radiator to the cooling device. I just think it's better to have it separate...sure there are more coolant lines and what not, but at least if the cooler starts leaking for some reason it won't mix with anything. It's good to know that you haven't had issues with that design though.
@tchid
I have never heard of a separate liquid-to-liquid cooler installed on a vehicle. And I don't see the difference. Either way you have transmission fluid beside coolant. Not only is there still potential for mixing, but the sheer complexity of such a thing would be just more connections and joints for leaks to happen. The in-radiator cooler is the most common and simplest solution, and it works perfectly well in an overwhelming majority of cases.