yikes- it's COLD and my coolant system is doing strange things!

A couple months ago I replaced the water pump, thermostat, and coolant. My Toyota ran great and the temps and heater were running perfect. Well the last couple of nights we've had down to -20 deg F temps and my baby is acting really weird.

Monday AM the heater wouldn't come on for a really long time and the temp gauge kind of "hunted" back and forth in the middle. Then the heater came on and the temp slowly rose until it got up to the red. I pulled into a gas station and pulled the radiator cap and there wasn't any pressure (no spillover) but the water in there was circulating and hot (radiator was hot, hose was hot, etc). I let it idle for about 5 minutes and the temp dropped back to normal and I drove 50 minutes to work and everything was fine.

Yesterday I drove home from work and the heater wouldn't come on (in about 5 min of driving) so I parked it and let it idle and it still wouldn't come on but it started "hunting" again. This time I cracked the cap and it had pressure.

This morning the same sort thing... heater wouldn't come on after idling/warming up for about 15 minutes and then when I started to drive, bam, it came on and then the temps started to come up. I got to work (only about 10 minutes of driving) before it got up too high. I cracked the cap and again it had pressure and plenty of fluid (I checked it later after the temps went down to where it wouldn't spill over and the fluid level was full).

What's going on? The thermostat is apparently working (circulating water through the radiator after the water in the block warms up) but why would the heater not come on until after I started to drive? Does the heater have it's own thermostat? And why is the temp climbing and why the first time this happened did the temp drop back down to normal and run fine after I checked it?

Also, the water/antifreeze in the overflow bottle looks kind of "slushy" even though I have it mixed 50/50 (orange kind). It's not frozen solid but has ice crystals in it. The water I can see in the radiator is all liquid though. Could this have something to do with things?

Thanks folks, appreciate it!

Joa '90 3.0L 4Runner w/238K

Reply to
Joa
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That's pretty suspicious. Do you have a coolant tester? You can buy one for a few bucks at a parts store. See if your coolant has the proper specific gravity. (The cheap testers don't actually tell you the s.g., they just give you an estimated freeze/boil point, which is fine.)

My first suspicion, if I had this vehicle in my driveway, would be that the freezing point of the coolant is too high and it is partially freezing and blocking the coolant circulating system. It eventually is remedied when the engine gets hot enough to melt the block. It'd be my first suspicion because it's the easiest and cheapest to test and to fix. If it's the coolant, partially drain it and add straight a/f or a mix, depending on how bad the tester says the problem is.

Then there's the question of *why* the coolant was bad. Again, my first guess, because it's the sort of thing I'd do if I wasn't paying attention, would be that you bought premix a/f and cut it with water as if it were straight. If you still have the bottle, just check it. If that's the problem, have a hearty laugh and go forth and sin no more. Another possibility is that you got bad a/f.

After that, it gets bad. Thermostat not functioning properly? Corrosion loosened by flush and fill blocking circulation? Leak in system (possibly caused by contraction of something in extreme cold) not allowing proper pressurization or letting water in somehow? Water pump sticking? Dunno. I just do the easy stuff. :)

D
Reply to
Dreamer

Same temps here, but mine is doing fine (it also got a flush, t-stat, and other bits this fall) so far.

First thought is stuck t-stat.

Low coolant level combined with stuck t-stat? If the water was hot, there should have been spillover.

That seems to go with stuck t-stat. If you bought an after-market t-stat, it may not have been the correct t-stat. Toyota uses a 2-state t-stat.

This can also point to a blown head gasket: no heat, over-heating engine. If you drive a vehicle and overheat it enough times, you can end up damaging the head gasket(s).

Warm, or hot? If it is a two-stage, or an aftermarket with a "hole" in it, it can allow some flow, which would be perceived as "warm." It should be _hot_.

This is absolutely no good. Coolant in the resevoir should be fluid at temps to usually -35F, standard mix. Test your coolant mix (both in the rad and the resevoir) with a known good tester.

Especially with the mileage, I'd consider the possibility that the head gasket(s) have blown, due either to wear, frozen coolant lines from low coolant mix, or overheat due to blocked t-stat/failing water pump.

With the truck warm, pull the oil-fill cap. Look for steam rising from the head, or some "milkshake" on the underside of the cap.

good luck! GTr '89 V6 4x4 DLX 198k (amongst others)

Reply to
gregory trimper

As a follow-up.... the trouble was the anti-freeze. It didn't apparently have a high enough mixture for the cold temps. As soon as I added more anti-freeze things started working normally again. I think I'm up to about a 60% mix right now.

Thanks for all your advice and help and if anyone else is having a similar situation occuring then now you know what to check :)

Joa

Reply to
Joa

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