Can't figure this out! Cooling system.

[JD_1990_GTS]

Ok, I have a 1990 Celica GTS that is about to drive me crazy. The first symptom I noticed was that the gauge was not warming up like it used to, it began reading slightly lower and the heater was less hot. I drove it like that for a couple months with no problems. One morning on way to work I noticed the gauge didn't move at all for several minutes, I was kind of alarmed and then saw it shoot up to almost 3/4 way and it started to overheat. I watched it it slowly cooled back down once on highway. From that point on, it kept doing the same thing. It would NOT warm up quickly at all, but once it started warming up, it would QUICKLY overheat. This makes no sense to me. Shortly after that, i noticed coolant leaks from a rear freeze plug, and the coolant bypass by the thermostat. The leaks DID NOT start until after all the overheating symptoms. It's almost as if pressure in the engine built up and created these leaks.
Out of ideas, I went ahead and changed thermostat and topped coolant off. I tested old thermostat, and it opened up in boiling water. It is now overheating less, but is still taking a LONG time for the needle on the gauge to move and it still rarely gets to where it used to be (which was dead in the middle for years). Can anyone shed some insight?

There is NO smoke from exhaust, no coolant in oil, and no oil in coolant. Car purrs like a kitten and runs flawlessly except for the crazy leaks and overheating. When I say it's leaking, I mean it's an extreme leak. I was pouring some water into radiator and as soon as I started pouring it in, it was dripping very fast and constant from freeze plug.

I'm also confused about how this cooling system works. I always thought the radiator inlet was on top and hot water from the thermostat hose ran DOWN the radiator and cooled and entered the engine from the bottom hose of radiator. This one is backwards?
The top hose gets very very hot, while the bottom one stays cool. Shouldn't the hot water from the engine make the bottom hose attatched to the thermostat housing hot?

Sorry for the length. I'll try and sum this up.

Car taking longer to warm up. 2 year old radiator and good coolant. fan works fine too.
Takes long to warm up then overheats VERY quickly.
Soon after develops weird leaks from bypass hose and freeze plug (seems like pressure built up in engine and blew through weaks spots)
Continues to overheat very quickly.
Change thermostat, and radiator cap seems better although still takes forever to warm up.
Began to overheat again yesterday.
Still leaking like crazy although it is intermittent. Will leak ferociously sometimes and sometimes not at all.....

[BLUEMEANIE]

Sounds like there's blockage in the system. Perhaps in the radiator. ...?

[JD_1990_GTS]

Originally Posted by BLUEMEANIE

Sounds like there's blockage in the system. Perhaps in the radiator. ...?

I flushed the 2 year old radiator out yesterday. Water ran through it fine. Also, how would that relate to it taking a long time to warm up? If there was a blockage, wouldn't it overheat very quickly?
I initially thought the same thing, a blockage which would maybe explain the leaks in random places after the car started overheating.

[BLUEMEANIE]

Not necessarily it could be letting enough coolant by to keep it relatively cool. At hwy speeds the air flow is doing the cooling.

Did you check for blockage at the pump or that the pulley isn't slipping/sticking a bit? If the belt is slipping above idle you might not be pumping enough thru the system. It could get full pressure until there's additional load on the belt. I'd check to see that the pulley isn't stiff, bearings aren't going out and that the belt is gripping correctly.

I had a Stingray that had the same issue and it turned out to be blockage that would lodge itself in the way as the system built pressure.

[BLUEMEANIE]

Originally Posted by JD_1990_GTS

Also, how would that relate to it taking a long time to warm up?

Coolant doesn't only cool, it evenly maintains operating temp and warms a cold system up to operating temp.



The breaks in the lines could be a result of excess pressure ... which is why I suggested a blockage.

Are the top and bottom hoses equally firm at idle and under load?

[JD_1990_GTS]

The upper hose is very soft. I can squeeze it easily although it gets VERY hot. The lower hose is soft as well but stays cool. That confuses me as well. Shouldn't the lower hose be HOT since it's where the coolant flows out of the engine through thermostat???

[BLUEMEANIE]

It definitely isn't getting pressure if the hose is soft and leads me to believe the pump might not be working correctly. You sure its working at all?

An engine can idle a long time with no coolant. Once its under load it'll heat up. If there's no air flowing past, it'll over heat. I've had a couple air cooled vehicles and the only problem I'd ever have would be traffic coming home after a long ride/drive on a hot day. The motor would already be warm and then I'd sit on the hwy black top in the sun. With no air flow I'd eventually start to over heat and have to pull off to let it cool down. Modern engines are designed to balance air flow and coolant, they're sealed up pretty well and if the coolant isn't flowing, the tight compartment can help them stay over heated.

[JD_1990_GTS]

HOw would I go about testing the pump??

[BLUEMEANIE]

Not sure off hand but since the system isn't getting any pressure (both hoses are soft) I think its a safe bet to say your pump is out. I'd just get a replacement. If it doesn't fix the issue, return it. ...or keep it for piece of mind and sell the old one.

The bottom hose is hot because the coolant isn't flowing and what coolant is in there is absorbing all the heat. Since its not able to pass thru the radiator it can't cool down.
The top is colder because little to nothing is passing thru it.

The freeze plugs and other fittings/connections are designed to leak with severe expansion/contraction. You might want to check and maybe replace those as well.

Have you flushed the block? Might as well do that when you pull the pump and check the plugs.

[JD_1990_GTS]

The top hose is the one that is hot. it's the one that connects to the block. The bottom hose is COLD and is the one that connects to thermostat.

[BLUEMEANIE]

My fault, thats what I meant. If the pump isn't moving the fluid its gonna soak up what ever heat is near by and not change temp.

[PEN]

I'm thinking you water pump is going bad have it change ASAP. along with it have a mechanic change your timing belt since they are done at the same time anyway also never add water to a cooling system its not good for the car.

Things to replace:
*coolant
*water pump
*timing belt
*radiator cap (tend to go bad fairly fast and will ruin engine)
*check for build up

[BLUEMEANIE]

^ PEN - Pure water is fine, just don't run it in the winter. Otherwise you're antifreeze is cut 50/50 with distilled water and does as it's name implies, which is to keep the water from freezing. Nowa' days you buy it that way, used to be you'd have to cut it yourself.


JD_1990_GTS - any updates?

[Bitter]

Actually Pen might have this one right, coolant also contains corrosion inhibitors and just adding it to water raises the boiling point by quite a bit so if your system suddenly looses pressure it's much less likely to violently flash boil and pop things open. Water is fine if you make passes on a drag strip and run a high pressure system, but in a normal car it's not so good since I doubt you want to change your water every month. Iron and aluminum, brass, copper, etc. all like to corrode one another, coolant's chemicals inhibit them (well try to) from passing electrons back and forth all willy nilly and eating each other. The aluminum parts are especially sensitive to this, here's 120K miles and never changing your factory fill coolant on a Dodge Neon...

[BLUEMEANIE]

Yep there are benefits to using coolant but distilled water can also be used. The down side is as you mentioned, and the key word is "try". Corrosion still occurs over time, coolant inhibits but does not prevent it.

Its really not applicable when we're talking about modern motors but my 1951 Chevy 1/2T has a 1948 low pressure (15psi oil, 7psi cooling), splash oiled, iron block 216ci straight six. It was a farm truck for almost all of its 60 years and has never had anything but water in it. Its a 3spd w/ 4:11 rear and has 114k mi so its safe to say its been driven at higher rpm and for extended periods of time. It ran great earlier this year until a valve stuck due to bad gas and bent a rod.