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Major Toyota Fan
1996 Camry LE
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74 Posts
Discussion Starter #1
The car is a high mileage 1996 LE 2.2 and is fairly well maintained. It sits outside. About a week ago, the car heater stopped working for my wife and it began to overheat after about 6 miles of driving. Ambient temperature was about 45 degrees. It was way down on coolant so I added more and when I test drove it everything worked perfectly including the heater. My thought was that it was so low on coolant that it wasn't getting much to the heater core. I've been unable to find any evidence of leaking, including at the heater core, so I was hoping I'd see something pop up now that I was looking for it. The car runs very well without any loss of power so a blown head gasket doesn't seem likely. It has a fairly recent timing belt and water pump. The thermostat is also fairly recent as are the hoses. The radiator is an almost new Denso (replaced new about a year ago) and I flushed everything and put in new Toyota red coolant at a 50:50 mix.

This morning it was much colder out, about 0 degrees when my wife left for work. She made it to work but the heater wasn't working again and the engine started to overheat. It didn't reach the red but it rose pretty high. About the time she got there the electric fans kicked on. I drove to her work about two hours later and found that the overflow tank was low again but the radiator barely took any coolant. Again no evidence of leaking. The car started and ran fine. I drove it home and the gauge stayed at exactly normal. However the heater still didn't work. When I opened the hood at home, the radiator cap was showing steaming but the engine took no coolant from the overflow tank like it did a week ago.

My gut reaction is that I have a bad heater core (maybe plugged) since that seems to be the wildcard here. I'm pretty sure it has never been touched and the car is around 240k miles. It seems strange that I'm not seeing or feeling any leakage at the core. My hope is that my fact pattern would give some obvious clues. Working on the car is a bit of a hassle right now since it's so cold and my garage is now taken with another immobile project car. Thanks in advance for your help.
 

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Super Moderator
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When I opened the hood at home, the radiator cap was showing steaming but the engine took no coolant from the overflow tank like it did a week ago.
This is indicative of a cap that’s not holding the pressure it should, which can cause overheating. Get a new cap; highly recommend paying more for an OEM cap. The aftermarket parts are hit/miss, often being bad out of the box.
 

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Another possibility is that the head gasket has failed. When these fail, they often breach between the coolant ports and the cylinder, which causes the combustion pressure to overpressurize the cooling system. Your ‘96 was built with an MLS gasket though, which is much less prone to failing than the composite gaskets used earlier.

Did you notice the coolant reservoir “boiling”, or blowing bubbles in it? That’s what my V6 did when it failed. There is a test kit you can use (see Amazon link below) which detects exhaust gas in the coolant. Some auto parts stores will loan you the tester, you buy the test fluid.

[ame]https://www.amazon.com/Block-Tester-BT-500-Combustion-Leak/dp/B06VVBSFTF[/ame]
 

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Major Toyota Fan
1996 Camry LE
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74 Posts
Discussion Starter #5
Radiator cap

I think the cap is OEM and pretty new but they are relatively cheap so it's worth a try. I just checked the purchase history and it is Genuine Toyota and it was bought May 2015.
 

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Major Toyota Fan
1996 Camry LE
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74 Posts
Discussion Starter #6
Other ways coolant is lost

My first thought would be loosing coolant from the radiator cap as well.

Everything seems dry around the cap and down the front and back of the radiator. The test would appear to be a new cap which is already on my wish list.

Another possibility is that the head gasket has failed. When these fail, they often breach between the coolant ports and the cylinder, which causes the combustion pressure to overpressurize the cooling system. Your ‘96 was built with an MLS gasket though, which is much less prone to failing than the composite gaskets used earlier.

Did you notice the coolant reservoir “boiling”, or blowing bubbles in it? That’s what my V6 did when it failed. There is a test kit you can use (see Amazon link below) which detects exhaust gas in the coolant. Some auto parts stores will loan you the tester, you buy the test fluid.

https://www.amazon.com/Block-Tester-BT-500-Combustion-Leak/dp/B06VVBSFTF

Wouldn't the car lose compression and run crappy if the head gasket failed? It runs really good. It can definitely explain the coolant loss without outward evidence however. The coolant tank has been very dormant every time I look at it (other than going down in coolant level). Nevertheless this seems like an angle worth pursuing.
 

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Wouldn't the car lose compression and run crappy if the head gasket failed? It runs really good.
Years ago I had a Ford Taurus blow a head gasket. Other than the overheating and excessive white billowing from the tailpipe, there were no other signs.

Other sign you could look for:

Coolant leaking externally from below the exhaust manifold
White smoke from the exhaust pipe
Bubbles in the radiator or coolant overflow tank
Overheating engine
White milky oil
Fouled spark plugs
Low cooling system integrity

I hope it's only the radiator cap in your case!
 

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'00 4 Cyl. Auto Camry LE
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853 Posts
It has a fairly recent timing belt and water pump. The thermostat is also fairly recent as are the hoses. The radiator is an almost new Denso (replaced new about a year ago) and I flushed everything and put in new Toyota red coolant at a 50:50 mix.

This morning it was much colder out, about 0 degrees when my wife left for work. She made it to work but the heater wasn't working again and the engine started to overheat. ...


... However the heater still didn't work. When I opened the hood at home, the radiator cap was showing steaming but the engine took no coolant from the overflow tank like it did a week ago.

My gut reaction is that I have a bad heater core (maybe plugged) since that seems to be the wildcard here. I'm pretty sure it has never been touched and the car is around 240k miles. It seems strange that I'm not seeing or feeling any leakage at the core. My hope is that my fact pattern would give some obvious clues. Working on the car is a bit of a hassle right now since it's so cold and my garage is now taken with another immobile project car. Thanks in advance for your help.

You should diagnose when cold - whatever is 'steaming', is a leak. Check everything, including hoses underneath, and radiator. It also sounds like your heater core is air-locked and/or the heater mix valve is not working correctly: the heater temp. mixing valve is underneath the hood, back firewall, on the '96 Camry here.


Suggest next time filling engine cold, radiator cap off, cabin heat on, and heat mix valve open (hot) to 'burp' the air out of the system: when the coolant level reaches the top of cap housing, replace the radiator cap, and check the level in the overflow bottle - any residual air purged, will drop the level in the overflow tank, which may take a few drive cycles - it needs to be monitored / checked, & filled accordingly.
 

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short-throw dipstick
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5,985 Posts
Consider renting a cooling system pressure tester to see if the system holds pressure. Some also come with attachments to test radiator caps.
 

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Major Toyota Fan
1996 Camry LE
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74 Posts
Discussion Starter #10
Parts ordered and new info

I have ordered a new cap, thermostat and the tester kit to determine if exhaust gases are in the coolant. Should be here today.

It is still not losing coolant and the radiator is full. I've run it a couple times at idle to see what it does in warmer weather. Not comfortable driving it where I could get stranded. That has raised some new developments:
  • I still have found no evidence of leaking at the suggested spots.
  • It seems to run a little rougher at start up than normal but it smooths out in a couple minutes.
  • When the car gets warm, the heater works but doesn't seem to get as hot as usual.
  • Even after it has run for several minutes, the gauge doesn't rise to the normal temp
  • When I touch the big hoses, the upper hose gets nice and hot but the lower hose seems to be very cool. Is that what would happen if I have a bad thermostat?
 

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Major Toyota Fan
1996 Camry LE
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74 Posts
Discussion Starter #12
Getting frustrating

Both ToyotaNation and the Camry Forum have been a godsend for me. I have been getting similar, excellent advice from both forums on this problem. Here is an update I posted on the Camry Forum:


I pulled the thermostat and it was not a Genuine Toyota part. I must have dreamed that or I'm thinking of a different car. I gave the old one and the new one the classic pot of boiling water test. The old one opened at well over 200 F, didn't open that far and seemed to open and close more slowly than the new one. The new Genuine part opened at around 195 F, opened a lot wider and closed consistently as the water cooled off. That seemed to track with the other symptoms. I put it back together with the new one in and it behaved pretty much the same way as before. I let it idle for about 20 minutes. It warmed up barely above cold on the gauge but the heater blew even hotter than before. I didn't mess with the heater controls because the heater seems to be working correctly. I'm not familiar with the controls and thought I might do more harm than good.

The upper big hose never rose in temperature and it didn't feel like it had much water in it when I squeezed it. Of course, since the system wasn't pressurized then with the cap off, it may not have much water in it. The radiator water never indicated that it was circulating using toyomoho's visual port test and the temp at the port never rose above 60 F. Assuming the flow pattern is from radiator into the lower hose into the block and the upper hose back into the radiator, it's starting to look like it's the water pump. Coolant doesn't seem to be moving. I have not mentioned this before but there does seem to be some noise I hadn't heard before when it starts up. If the water pump has a seized bearing, I always thought that the timing belt would jump a tooth or come off completely, trashing the valves, etc.. But like I've consistently said the engine runs very well with plenty of power. I suppose it could still be the broken off impeller blades issue although that wouldn't seem to make noise.

The block exhaust gas test requires that the coolant be hot which means it needs to circulate. I think I need to eliminate the water pump first. Any thoughts?

Addendum: I just read my prior posts and the car had a hot upper hose and a cool lower hose when I reported earlier. Now I am more confused than before!


Thanks again for all your help.
 

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I pulled the thermostat and it was not a Genuine Toyota part. I must have dreamed that or I'm thinking of a different car. I gave the old one and the new one the classic pot of boiling water test. The old one opened at well over 200 F, didn't open that far and seemed to open and close more slowly than the new one. The new Genuine part opened at around 195 F, opened a lot wider and closed consistently as the water cooled off. That seemed to track with the other symptoms. I put it back together with the new one in and it behaved pretty much the same way as before. I let it idle for about 20 minutes. It warmed up barely above cold on the gauge but the heater blew even hotter than before. I didn't mess with the heater controls because the heater seems to be working correctly. I'm not familiar with the controls and thought I might do more harm than good.

The upper big hose never rose in temperature and it didn't feel like it had much water in it when I squeezed it. Of course, since the system wasn't pressurized then with the cap off, it may not have much water in it. The radiator water never indicated that it was circulating using toyomoho's visual port test and the temp at the port never rose above 60 F. Assuming the flow pattern is from radiator into the lower hose into the block and the upper hose back into the radiator, it's starting to look like it's the water pump. Coolant doesn't seem to be moving. I have not mentioned this before but there does seem to be some noise I hadn't heard before when it starts up. If the water pump has a seized bearing, I always thought that the timing belt would jump a tooth or come off completely, trashing the valves, etc.. But like I've consistently said the engine runs very well with plenty of power. I suppose it could still be the broken off impeller blades issue although that wouldn't seem to make noise.
A few things:

The water pump pulley runs on the flat side of the belt on this motor, not the toothed side. So if the pump was starting to seize up, it'll slip quite a bit before it tears up the belt.

This motor is non-interference, so if the timing belt fails, it doesn't damage the motor.

The water pump impeller is plastic, and molded onto the metal shaft. It's possible it's come apart. Never seen one here on the forum, but it's a possibility.
 

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If it does not overheat with the heat setting all the way to the cold side, then I'd say you have a plugged up heater core. I think you have 23 years worth of sediment in the bottom of the radiator killing its effectiveness.
 

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short-throw dipstick
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1The water pump pulley runs on the flat side of the belt on this motor, not the toothed side. So if the pump was starting to seize up, it'll slip quite a bit before it tears up the belt.
No, 5S water pump has a toothed sprocket; it's 1MZ that runs with the flat side.
 

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Super Moderator
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^Ah, right. I mistakenly thought the OP had a V6.
 

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'00 4 Cyl. Auto Camry LE
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853 Posts
... I put it back together with the new one in and it behaved pretty much the same way as before. I let it idle for about 20 minutes. It warmed up barely above cold on the gauge but the heater blew even hotter than before. I didn't mess with the heater controls because the heater seems to be working correctly. I'm not familiar with the controls and thought I might do more harm than good.

The upper big hose never rose in temperature and it didn't feel like it had much water in it when I squeezed it. Of course, since the system wasn't pressurized then with the cap off, it may not have much water in it. The radiator water never indicated that it was circulating using toyomoho's visual port test and the temp at the port never rose above 60 F. ...
The block exhaust gas test requires that the coolant be hot which means it needs to circulate. I think I need to eliminate the water pump first. Any thoughts?

Addendum: I just read my prior posts and the car had a hot upper hose and a cool lower hose when I reported earlier. Now I am more confused than before!


Thanks again for all your help.
The purpose of the thermostat is to -block- coolant flow to the radiator, until the engine heats the coolant. The cabin heater being warmer is a good sign - it's supposed to be when the thermostat is closed: the cabin heater is directly off the engine block.




Your new thermostat is not opening, to allow coolant flow to the radiator.

Why, it could be too cold w/ the radiator cap off, to allow the unpressurized system to reach operating temp. within 20 minutes ... with air in the system.

Or, the new thermostat could be installed incorrectly, been there - done that. If below offers no improvement, I would re-check my work, if here.

Run w/ radiator cap installed, fully heat-soak the motor, monitor coolant overflow tank level..

If there is air in the system, coolant level in the overflow tank -will- drop after thermostat opens: make sure to monitor closely, and keep it above (low) level.




Consider checking coolant level @ radiator cap after letting sit for several hours / engine cold, re-top level as needed.

Hope this helps.
 

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Major Toyota Fan
1996 Camry LE
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74 Posts
Discussion Starter #18
FSM and Haynes

No, 5S water pump has a toothed sprocket; it's 1MZ that runs with the flat side.
It is an 5S engine. Without anything apart I can't really verify this but the FSM and Haynes show the flat side of the belt running the water pump.
 

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'00 4 Cyl. Auto Camry LE
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853 Posts
@rbuswell - if you 'boiled' that new thermostat when you were doing your testing: Consider trying a (2nd) replacement thermostat, if you are still having issues.
 

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Major Toyota Fan
1996 Camry LE
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74 Posts
Discussion Starter #20
Lots of great thoughts

The purpose of the thermostat is to -block- coolant flow to the radiator, until the engine heats the coolant. The cabin heater being warmer is a good sign - it's supposed to be when the thermostat is closed: the cabin heater is directly off the engine block. That was my feeling too.

Your new thermostat is not opening, to allow coolant flow to the radiator. Doesn't it seem odd to you that the engine block side wouldn't get hot enough to open the thermostat in 20 minutes regardless of air in the system?

Why, it could be too cold w/ the radiator cap off, to allow the unpressurized system to reach operating temp. within 20 minutes ... with air in the system. Same as above.

Or, the new thermostat could be installed incorrectly, been there - done that. If below offers no improvement, I would re-check my work, if here. It doesn't appear that it can be installed incorrectly in this engine. There isn't enough room in housing on the radiator-side for it to fit with the temp reading side of the t-stat in that direction.

Run w/ radiator cap installed, fully heat-soak the motor, monitor coolant overflow tank level.. I have not tried running it with the new thermostat and the new cap on. I will do that. Another poster suggested that I start the engine cold and watch the flow in the radiator. His belief was that the engine should get hot enough to open the t-stat and, if the pump was working, I would see the water flow in the radiator. Can't really do that safely with a hot engine.

If there is air in the system, coolant level in the overflow tank -will- drop after thermostat opens: make sure to monitor closely, and keep it above (low) level. Yes that makes sense.

Consider checking coolant level @ radiator cap after letting sit for several hours / engine cold, re-top level as needed. Coolant loss appears to be way down from earlier but I haven't been running the car for nearly as long. Concerns about a blown head gasket are still in play. Unfortunately I can't use my new exhaust gas block tester if there is not coolant flow.

Hope this helps.
More info after your suggestions
 
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