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2001 4runner sludgy coolant

I have a 2001 toyota 4runner 6-cylinder 3.4L engine with about 197xxx miles on it. I just took it in for an oil change a few weeks ago and when they checked all the other fluids in the truck they said the coolant seems sludgy and dark. Also the check engine light and vsc trac and vsc off lights came on, a week or so before the oil change. I’m pretty mechanically inclined and do almost all my work myself with the limit of the tools i have, but i can’t seem to figure out what is causing this. any suggestions or answers would be greatfully appreciated.
Erich in NH

“i can’t seem to figure out what is causing this

What’s the “this”? You just mentioned a whole bunch of things.

In terms of the cooling system, have you followed the service manual regarding cooling system servicing? Sludgy, dark coolant can just mean old and never changed. It could also mean that you were at a quickie-lube type of place where they specialize in selling services. Did you have a look at the coolant yourself? Is it dirty? Or does it look contaminated by something else (like oil or transmission fluid)?

As far as the warning lights go, you need to have the car scanned for error codes. I’d start with a free scan at an auto parts store. (Many will scan for free). If you do this write down the exact codes as they appear on the scanner - format: “P1234” Whatever comes up there could very well tell you about the vsc issue.

Have you ever done a cooling system flush and refilled with fresh coolant? Sludgy and dark coolant is a bad thing. It could mean that oil of some type has invaded the cooling system. I would get it checked out by a good independent mechanic. It may be a minor problem but it could also be a major one as well.

my thought is that the lights came on due to the coolant issue so i think its all one problem. I took it to an independent garage for the change so i don’t think they were trying to BS me. How ever i have never done a coolant change so i will look into doing that and if that doesn’t help ill probably take it in to my mechanic and see what he says.
Thanks a lot.

If you’re 11 yrs and almost 200K on the same coolant then your biggest problem in general is going to be a lack of maintenance. You’re way overdue even if the coolant in there is a “long life” coolant.

The engine & vsc lights have nothing at all to do with the condition of the coolant.

the truck hasn’t been mine since day one, so i don’t know if its been changed before. its only been mine since about 175xxx when i got it. but it gets regular oil changes and bearings and such have been replaced, timing belt was done, along with lots of other things over the past couple of years at inspection time.

If you haven’t done regular coolant drain and refills, the check engine could be related. If, for example, the thermostat was now damaged, it could cause the check engine light. You would want to change the thermostat at the same time that you change the coolant.

BTW, don’t flush, but be sure to have the block drained as well as the radiator.

Get the code checked first.