5SFE overheating... I'm stumped

[Cuda72]

Hi all,
I’m stumped working on my niece’s 1994 Camry 5SFE. It’s been overheating regularly. The first time my niece brought it over to me, I changed out the thermostat with a Toyota OEM unit with the jiggle valve in the correct location. I also changed the radiator cap with a parts store unit (I've tried two different caps with no differences). At the same time I flushed water through the block and through the radiator with the garden hose. After refilling with a 50/50 mix, I let it idle for like 15 minutes with the cap off and the heater on full blast. No overheating.

The next day I drove it on the freeway for ~10 minutes and the temp was right below halfway where it should be. After I got off the freeway in stop and go traffic the temp gauge shot up to the red. I parked it for a while and after letting it cool off I took it on the return trip and this time it shot up to the red on the gauge on the freeway itself.

I’ve been thinking it’s the head gasket because there is some white smoke at start up. So this weekend, I pulled the plugs and did a compression check and all cylinders read 175 or 170. I drained the radiator and flushed the radiator again. Then I refilled the radiator and let it idle for 10 minutes with the cap off. Put the cap back on and took it for a 10 minute stop and go traffic drive. The temp gauge never moved off of slightly below halfway. After returning I left it running in the driveway and popped the hood. I noticed that the overflow tank was bubbling and when I looked back at the temp gauge it was above the max range. I rev’ed the engine to like 3000 rpm and that brought the temp back to normal in like 10 seconds. I let it keep idling and like 4 minutes later it shot up from normal to red in like 5 seconds. Is that even physically possible???? Could the gauge be bad? Would a leaking head gasket cause it to be fine most of the time and then just spike the temperature up like that even while idling?

While this was happening, both hoses are tight and hot. I think the radiator fan switch is bad because the fans all on all the time (I pulled the connector and the fans stayed on… then I jumpered the connector and the fans shut off). Anyway, the fans being on all the time should only help with the overheating right?

I couldn’t find a local radiator shop that does the CO test, so I guess I should either just tear in to it to replace the head gasket or I should buy the Napa kit.

Sorry for the long post, just wanted to get all the info out there. Any ideas?

Thanks,
Travis

[haux]

I'd be stumped too. When it comes to overheating, my checklist is circulation (waterpump, thermostat), pressure (rad. cap), and radiator fans.

Seems like you've got everything covered except the water pump. Have you ever been able to feel coolant circulating through the system by squeezing the upper hose? I don't know of any sure way to test the pump. I'm thinking, what if pressing the accelerator at idle somehow initiated the pump to circulate coolant when it was overheating in your description?

If the temp switch at the radiator was bad, the fans would always be on and it would only cause the coolant to stay cooler.

There's also a coolant temp sensor for the engine, but as far as I know, that only reports the temperature to the gauge. I could be wrong.

As for the bad headgasket... was the original coolant pretty clean?

[carsrus]

Originally Posted by Cuda72

Hi all,

I rev’ed the engine to like 3000 rpm and that brought the temp back to normal in like 10 seconds. I let it keep idling and like 4 minutes later it shot up from normal to red in like 5 seconds. Is that even physically possible???? Could the gauge be bad? Would a leaking head gasket cause it to be fine most of the time and then just spike the temperature up like that even while idling?

Thats a sign the pumps bad and not circulating enough at idle. The compression numbers are good so I doubt its a head gasket. Its probably spiking because once you give it some revs the cooler coolant from the rad circulates into the temp sender/block.

[91MR2quickNA]

Originally Posted by haux

There's also a coolant temp sensor for the engine, but as far as I know, that only reports the temperature to the gauge. I could be wrong.

The coolant temperature sensor is for the ECU.

The coolant temperature sender is for the gauge.

If the sender gauge connector is grounded during operation, the gauge will read fully hot. You'll find the sender on the water outlet (the top radiator hose goes to it). It should be underneath it. You might just have a bad sender.

You could verify the actual coolant temperature with a thermistor or OBDII live data feed.

[CDJr]

I agree with carsrus...the impeller on those pumps are prone to disintegrating over time and will stop pumping water. The one on my wifes car had similar symptoms and when I removed it there were 2 or 3 blades left on the impeller and they were razor thin...the other 7 or 8 were simply rusted away. Ive since run across the same problem several other times. You may be able to reach through the t-stat housing and feel it to save the trouble of pulling it off, just to make sure. But Id definitely check the pump before going to all the trouble of pulling off the head. Hope this helps.

[Cuda72]

Thanks all for the advice. I forgot to mention that a year and half ago I changed the timing belt and at the same time put on a new water pump as well.

What's strange to me is that it's overheated both on the freeway running 65 mph and while sitting idling at a stoplight. I might try changing the gauge coolant temp sender as well as checking the wiring.

Thanks,
Travis

[Cuda72]

An update....

Today I pulled off the radiator cap and topped off the radiator with distilled water. Started it up and idled it for 40 minutes with the cap off and heater on full blast. There was foaming in the radiator inlet that would occasionally bubble over but the temp gauge never moved off of normal. Put the cap on and did the same 10 minute city drive with the AC on high. Temp gauge never moved. Pulled in to my driveway, put it in park, turned off the AC and within 10 seconds the temp gauge was above max. Popped the hood and sure enough bubbling in the overflow tank.

Reved the engine up again around 2500 and within a minute or so it came back down to normal temp and no bubbling in the overflow tank. Waited two minutes or so and then put it in reverse to drive around the block and within 100 yards it was in the red again. Pulled back in to the driveway and repeated the same steps. I tried turning the engine on and off to see if that made a difference, but it didn't.

I'm confused. It doesn't even seem physically possible for the engine to go from say 190 to 240 degrees in like 10 seconds even if the water pump is not working and the thermostat is closed????

If it was a head gasket wouldn't it do it more often? Other then the foaming when the cap was off, there doesn't appear to be any oil in the antifreeze or antifreeze in the oil. Any other thoughts? Should I try another radiator cap?

Thanks,
Travis

[BamZipPow]

Did you put in an OEM or aftermarket water pump?

Did you verify that you are actually gitting water flow from the water pump? I would suspect you would have to do it with the engine cold and pull the heater hose and see if it's streaming through there or not.

[71Corolla]

When in doubt, remove the thermostat completely. Run the car and top off the rad with water and some used coolant you have left over from draining when you pull the stat. Looking into the radiator you should easily be able to see the fluid streaming along at all times. If it doesn't, the waterpump is not doing it's job.

If the car still overheats with no thermostat, you either have a clogged radiator and/or coolant passages, a bad water pump, or much less likely but possible, a blown head gasket. With no thermostat the car should never get above just slightly warm no matter how much you drive it.

edit - the proper way to drain all the fluid out of the system is remove the drain **** (stop laughing) which is at the "back" of the engine (firewall side). That is the lowest point of the cooling system, it's fairly easy to get to if you drive the car up on ramps.

[CDJr]

Whatd the old pump look like when you replaced it? I think the easiest way to eliminate the pump as the culprit would be like 71Corolla suggested and remove the t'stat, backflush it and refill it and see how it acts and the easiest way to test for the blown head gasket is to let it cool down, then start it up and see how quickly the hoses build pressure. If the head gasket is blown, the pressure will build very quickly in the cooling system and the hoses will tighten up faster than normal However, its beginning to sound more like a fan or electrical issue.

[Cuda72]

Thanks for the ideas. I'll pull the thermostat tomorrow and backflush again. I'll also see if I can get to the back drain plug. When I pull the thermostat I'll see if I can feel around for the water pump.

I'll report back tomorrow.

Thanks,
Travis

[fenixus]

Originally Posted by Cuda72

Thanks for the ideas. I'll pull the thermostat tomorrow and backflush again. I'll also see if I can get to the back drain plug. When I pull the thermostat I'll see if I can feel around for the water pump.

I'll report back tomorrow.

Thanks,
Travis

you need to put car on ramps or jack stands and slide yourself on your back under car with head toward rear to see the drain "****" on the back of engine block, once you see it you will know. i think you can attach a hose to it for easier draining otherwise it will be flushing out straight on your face

when you said you flushed the rad and block first time, you did it through radiator using tap water (garden hose) ? and then refilled with 50/50 mix ?

if yes then half of that water stayed in engine block and you topped of radiator with 50/50 mix making a lean coolant mixture of around 25% coolant and 75% tap water (corrosive!!).

I suggest using only distilled water for any flushing purposes and then topping up radiator with concentrated coolant (so it mixes to 50/50 with left over water in engine block).

you can also burp upper radiator hose a few times when topping up radiator to make sure there is no air in it. also after idling for 10 mins, shut it down, wait a few minutes and open the rad cap, if coolant level is below the cap top it off (it means there was air still in it). also put 50/50 mixture in return tank past the full mark (make it literally full), engine will suck it in over night. it's better to initially overfill it then to fight with air in system again the next day.

i don't quite like idea of using aftermarket water pumps. used one once and it died in less than 2 years (shortly after flushing radiator). now running OEM pump again and new thermostat and hoping it holds longer.

also get OEM rad cap from dealer, those aftermarket ones just do not hold pressure right. if there is no pressure in system the coolant mixture will boil at 220F (water only) or slightly above it when mixed with coolant concentrate.
when running pressurized the boil point shifts long way above those temps (higher pressure, higher boil point).

since you saw the water bubbling in return tank on one occasion then i think your coolant temp sender is fine and was showing correct voltage on dash.

good luck!

[71Corolla]

I agree, it's never a good idea to flush with tap water it's loaded with minerals and who knows what else. But if you can't help it, draining the system from the lowest point will at least get most of it out.

I posted this in another thread, use a proper funnel to fill the system. Without it, it takes 10 times longer to deal with getting the air out.

[Cuda72]

Well I only had an hour to work on it today, so I pulled the thermostat and ran it without that just to eliminate the thermo. I did the same 10 minute loop and this time it went from normal to in the red about 3/4 of the way through the drive (again it just spikes up very quickly). After that it wildly fluctuated between normal and red... sometime cooling down at idle and other times cooling down at speed.

When I had the thermostat housing off, I looked at the water pump blades and at least the ones that are visible looked fine. I can't remember if it was an Aisin water pump or an aftermarket one that I installed last. When I refilled the radiator after pulling the thermostat I could see the water flowing so the water pump appears to be working at least some of the time.

The hoses didn't feel that tight to me and of course with the thermostat out, both the top and bottom hoses were hot. Should I try taking it to a radiator shop and having them flush out the whole system?

Thanks,
Travis

[fenixus]

i think you might have some dirt or debris clogging the radiator. professional pressure flush won't hurt.
otherwise it might be a sign of water pump failing maybe ? do you have any leaks from WP weep hole or louder pump operation ?

when you were flushing the rad, have you seen any black pieces of "dirt" in old coolant ? was it discolored in any way ?