Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

'94 Pre-Tacoma Coolant Gelled

Hello everyone,
I have a 1994 Toyota Pickup with about 270k on the odometer. I recently flushed my radiator like I do every three or four years. When I opened the hood today and popped open the radiator cap, I noticed that there was gel around the cap threads. This really bothers me. It might be nothing, but I want to make sure.
P.S. If it helps, I mixed O’reily brand and Prestone brand coolant. The Prestone said it was compatible with all colors.


I would stop flushing the system, especially if you are using a chemical flush. Just drain both the radiator and the block and if it doesn’t come out in blobs, you are good to go. Refill with either premix or mix your own using distilled water. I like to mix mine a bit rich, up to 2:1 antifreeze to distilled water. Always mix in a separate container, like old antifreeze bottles and refill and bleed the system.

“I mixed O’reily brand and Prestone brand coolant”

I don’t care what the jug says. I never mix different brands of coolant.

Provided you didn’t use any flush chemicals, just flushed with plain water, I doubt there would be any problem mixing the two brands of coolant you mention. I’m betting you didn’t mix up the water and coolant in a separate bottle, instead you put in the water and the undiluted coolant into the radiator separately. And you just spilled some undiluted coolant in the process on the radiator fill tube. Undiluted coolant is sticky stuff, and it is now sticking to the threads of the radiator cap.

If both brands are universal green, it’s fine to mix

However, I would not mix Dexcool and G-05 or red asian coolant and universal green

Caterpillar issued a service bulletin on gelling antifreeze onetime seems that a too high concentration of Glycol can sometimes Gel,remember Glycol needs water to function correctly(I guess a sort of synergy) did buy a jug of texaco brand I think it was that was jelled in the jug-Kevin

Mixing compatible coolants is not an issue unless either one of them is OAT formulation and the seal is compromised. OAT and air = gelling. If its limited to the threads perhaps that’s all that was exposed.

I was always told that the max concentration for antifreeze is 60% antifreeze and 40% water.

That is pretty much correct. Up to 2/3 coolant and 1/3 distilled water

The so called full strength is not 100%, it already has some water in it (about 4%). In theory, 67% yields the lowest freeze point, but because there is already a little water in the full strength, you can go 70% from the jug to 30% distilled water.

I mix 2:1 mainly to get additional corrosion protection. I live in the south so I don’t go that rich for the freeze protection, only for the extra corrosion protection.

It does seem that most antifreeze testers on the market don’t read past 60% though.

The brand name is not the coolant type.
The o.p. has not identified the TYPES of coolant in the two bottles nor how much water was added to or pre-existed in them.
Pretty hard to answer the question with no new info input.

You probably need a new radiator pressure cap.

If the cap doesn’t hold the proper pressure, water vapor can escape from the neck for the radiator cap leaving behind gelled antifreeze.