Radiator Sludge, with pictures...

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Feb 26, 2004
This is a continuation of this thread, but since I have some interesting pictures, I want to start a new thread...


So, after poking around inside the fill hole of the radiator and running into what felt like an inch thick of sludge, I assumed the whole radiator was like that I wanted pull the tank off to see how bad it was.

Turns out there was a ton of sludge around the fill hole, and a number of rows on that side of the radiator were no doubt plugged up. But the rest of the radiator looked surprisingly good. At least from the top. I should mention that I had a radiator shop clean the radiator yesterday and it's possible there was a lot more sludge that was flushed out before these pictures were taken. However, if they did flush it, they didn't flush it that throughly, because I still had pink coolent coming out of the lower tube when I brought it home.

As for the sludge, it's actually sort of greenish/grey. This rig had green coolent in it, when I bought it early last year. I'm sure it's had both red and green over the years with the two prior owners and I flushed it and put red back in. I don't know if that means anything. I read the posts were owners who've only used Toyota red since new have had sludge, but don't know if it's the same as this sludge.

The rig has 96K miles on it, 1995 FZJ80. The radiator would need to be cleaned and probably rodded out to save, but I think I'll be going to get a '94 copper 3 core, just to have a nice new part, plus I think I might have damaged it when I dropped an alternator up against it that I was pulling out the other day.

I haven't removed the bottom tank yet. I don't think I'd find much if I did.

Pic 1: The sludge pile on the passenger, collected all around the fill hole. This must obviously be a nice low pressure area in the radiator for crap to settle on.

Pic 2: The inside of the tank, with more sludge around the cap.

Pic 3: The rest of the top row, driver's side with minimal sludge.

This is sort off topic, but I hear a lot stories of guys replacing the entire radiator when the front nipple breaks off. Seems like replacing the top tank only would be a very easy fix if the rest of the radiator was in good shape.
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Hmm, I wonder if we actually need to change the radiator after 100k miles to obtain best cooling efficiency for the engine then. I have 3 cruisers up to date, but none shows sludge like that at the fill hole.
That was a pretty sad job of the shop cleaning the radiator if you still had original pink fluid dripping out of it when you picked it up. That's just a sad statement on them.

So, importantly - how are you going to get all those tabs bent down again to reseal it?


Can you take a closeup shot of the nipple area that gets broken by accident? I'd like to see the material thickness on the inside of the tank if possible.

so, is the casting sand still the favored explanation?

Brian, try to collect and keep the stuff. Maybe we can find a good suspension / floatation agent that would allow us to do good flushes to get rid of the stuff.
Casting sand? That's the first time I heard that one. Very interesting thought.

I do plan to save the gunk. I would love to find out what it actually is some day.

As for bending the tabs back down, most likely I won't be saving the radiator, but if I did, would take it to a better radiator shop and have them rod it and reseal it for me.
The casting sand theory is wrong IMO. It's a bit of a stretch to say Toyota had not figured out how to clean blocks after casting them. To me, the coolant precipitate from poor cooling maintenance or mixing coolants (a known documented issue) is it.

Well, after spending hours reading multiple threads on this issue, I'm sure nobody wants to rehash this yet again without brand new evidence, but I'll never forget how Dan and others have run only factory Toyota red and did regular changes and flushes and still had the sludge.

That said, my sludge has a distinct green tinge to it, which indicates to me that it's related to the green coolent that was in the rig before, somehow.

I haven't tried to dig it out yet, but the very bottom of my overflow bottle has a distinct dark grey sandy like material in it.

Based on some of the threads, including the coolent filter thread, I'm wondering if there are several different types of sludge from several different sources.
Sludge in 1990 Toyota

I want to thank you. i have a 1990 Toyota corolla and i am having the same problem. i have placed antifreeze in the car, but it was still running hot. i have had the radiator replaced as well as the thermostat, and we couldn't figure out where the sludge was coming from. but thanks because now we know how to rectify the situation. After flushing the radiator, what antifreeze is recommended so this issue won't occur again.
i think it's a problem with the toyota red imho. I know several here that have run nothing but toyota red, proper maintenance ect... and they still get the sludge in some part of the cooling system.

I wonder if those that have done a complete flush and are now running "other" coolant are seeing the sludge?

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