Hello guys,

I coming here as a last resort and to get a counter opinion from my mechanic. Background: it is a 95 camry 4 cylinder with 199,000. Was sitting outside for 3 years but has been running normally for a year now after tune up. Switched from normal oil to synthetic about 8 months ago.
Problem happened a few weeks ago when overflow boiled over without my noticing. Realized fans weren't coming on unless top plug was taken off to bypass. Replaced Thermostat, Fan relay, temp sender, water pump, flushed radiator. Now fans run continuously when ignition is on but don't help prevent overheating. Radiator Antifreeze/oil levels aren't going down and don't look milky/mixed. Radiator checked and functioning normally. No smoke from engine. Don't notice any liquids coming from exhaust. Engine runs smooth with normal power. Heat works as normal and turning it on initially helped to bring heat of engine down but now has no effect. Revving engine brings down temp slightly. Takes about 20 minutes of hwy driving to start overheating and then will do so constantly until temp reaches red. Goes slowly up to about 3/4 hot and will hover there and then slowly goes to red. Mechanic feels only option left is head gasket but I haven't seen any proof that this is the issue. He seems to be using the trial and error method and this is the last option remaining.
What other problems might this be or what is the most likely? Plugged catalytic converter, air being trapped in radiator, temp control valve stuck on heated air intake, fan clutch? The car is only worth 2,000 and I I've already put in 600 and really don't want to put in another 1k for head gaskets!! Camry experts please give me some insight, I'm sure someone else has had a similar problem. Thanks a lot and I am looking forward to finally figuring this out.

Scott

 

Overheating issues can be difficult to diagnose but not impossible to solve.

When the overflow tank boiled over did the engine temp gauge go up?

How was the radiator function checked? It should pass water freely from a garden hose.

Issues such as the heater and engine revving helping to bring down the coolant temp point to poor cooling system operation. The Camry’s cooling system should be able to keep the engine cool in any type of driving, stop and go on a hot day, pulling a trailer, etc. The temp gauge needle should remain rock steady once the engine is warmed up.

The coolant fans are typically only required when car is operating at very low MPH or stop and go driving. The also turn on when the AC compressor is working. Operating on continuous basis might even be a determent at highway speeds as the spinning fans may actually slow down the airflow passing through the radiator.

What happens to the coolant temp if the engine is just idling?

Is the plastic air shield still attached to the under side of the car. This would gap the space between the engine and radiator.

A plugged CAT should also cause a lack of engine performance. A plugged exhaust system can be checked using a vacuum gauge.

The 4 cylinder Camry has no air bleed system when refilling coolant. When the engine is cold remove the radiator cap. If coolant is present all the air has been bleed out, if not add more coolant.

The fans do not have any clutch, they are electric and should only turn on when the coolant temp goes over say 200Fish or when the AC compressor is running.

The coolant does run to the air intake but it should not have any temp valve. Coolant goes in and comes out.

As to a head gasket. This engine can blow a head gasket if overheated, not uncommon. If the coolant system still had coolant in it (to effect the coolant temp sensor), the lack of fan operation should have caused the temp gauge to rise, did this happen?

A blown head gasket may or may not result in oil in the coolant or coolant in the oil. The engine may also run great. Typically the coolant water drops. Sometimes suddenly, sometimes it stays at a normal level for weeks.

If a head gasket issue, some event must have caused the engine to overheat, heat gaskets do not just fail. Do you have an idea of what this event could have been?

A compression test may or may not find low compression resulting from a blown head gasket.

If the radiator cap is removed (engine cold), once the engine is warm a blown head gasket can result in coolant being driven out of the radiator fill point as the engine is revved. This is due to air being introduced into the coolant system.

In my opinion the best way to check for a blown head gasket is to a test for exhaust gases in the coolant system. The test is called a “block test.” It uses a tube filled with a chemical that attaches to the fill point of the radiator. When the engine is running if exhaust gases are present in the coolant system the fluid will change color. At times this is the only test that points to a blown head gasket. The test kit costs about $50 at auto parts stores. Perhaps a little pricey but when used correctly it should provide a yes or no answer to a head gasket issue.

Air in the coolant system from a blown head gasket can cause all kinds of cooling problems.

A bad radiator can also cause overheating problems. Did the mechanic add any coolant system cleaners to the radiator? Have had issues where adding these chemicals results in a plugged radiator from all the debris "cleaned" from the engines cooling system.

Ask your mechanic to do a block test for exhaust gases.

The link below has a list of reasons for engine overheating and how to check for them. Suggest you go down the list and compare to what the mechanic has checked.

http://www.aa1car.com/library/overheat.htm

If you do go the head gasket replacement route have a machine shop check the head for cracks and warpage. If minor warpage the head can be machined. These operations will add more cost but are cheap insurance. Most of the cost for replacing a head gasket is labor.

If you really want to do the job right have the machine shop replace the valve stem seals. These tend to harden with age and result in a puff of white smoke at cold start up that only gets worse with time. The car sitting for several years is also not good for these seals.

 

Thanks so much for the long and very detailed explanation; I wasn't expecting such a thorough response. I agree no problem is impossible but within my budget constraints and the value of the car it just might be this time.

The first time it boiled over I can only assume the temp gauge was in the red or near (as it has been since) but I didn't actually realize the overheating at the time.

Radiator is fairly new and was taken out specifically to test it on a machine (not sure of the name), and was supposedly okay.
It has been fully flushed and is functioning properly.

Temp gauge for past years has remained rock steady as you mentioned and only recently has acted up.

Since the mechanic still can't figure out why fans won't operate as normal they must stay on all the time. Old fan relay was replaced (no fan function before) with new one and now they run 100% of time.
AC is not working as condenser is broken so this would have no effect.
How likely is the running fan at hwy speeds (both left and right fans) contributing to the overheating? Because it only seems to start overheating at hwy speeds and then continues thereafter. I suppose I could test it by unplugging fan and then driving all hwy miles to see if overheating starts? Engine doesn't seem to start overheating at idling unless already started while on the hwy. But this is hard to say for sure because it usually takes 20min of hwy to start the overheating.


Nothing happened out of the ordinary before the overheat. So as you said, there was no reason for the head gasket to go out or fail as far as I know.

So my safest bet is to do the block test. What about also the cylinder leak test? Is this as accurate and indicative as the block test? Also how about monitoring overflow tank/rad reservoir while car is running to see if air bubbles are being created (not ones from boiling)?


Not sure about plastic shield, car is still at garage.

Coolant has been full and non-leaking the entire time, except for the times it bubbled out of the overflow after boiling. And the gauge went up when the fans initially went out and now it still does when the fans are on full time. I've been dealing with this problem for >3 weeks and still no noticeable coolant reduction so it makes me wonder if it really is the head gasket.

Mechanic asked me if I had added any "stop leak" into the radiator and I answered no because it was only a year old and I didn't think this had been used.

What reason could there be for the original fan relay doing nothing in regards to fans but the new one making the fans run 100% of the time. Temp sender and thermostat are new. Could the remaining sensor be causing the problem (forgot the name of it)? Also when the other sensor that reads the temp for the interior heat gauge was installed it kept malfunctioning giving the wrong temps. When wiggled it would change but it wouldn't stay at correct temp. When old one was reinstalled the temp gauge worked fine. Could this be related to anything?

Finally, I've had a total of at least 3 reservoir boil overs in the past 3 weeks due to this problem. When I've noticed I've pulled over and let it cool down. Radiator has never been more than 90% empty. No steam or smoke. If I didn't have a head gasket problem before what are the chances that this boiling over has caused a HG problem or other cracking/warp-age in the engine?

Hope my answers help in narrowing the problem. And again, I really appreciate your friendly and helpful advice. I'm somewhat of a car novice but want to logically think things through before heading forward. Sorry if I added too many new questions.

Thanks,
Scott

 

The Camry coolant fan system is not that complicated but it does have 3 relays. To understand its workings a wiring diagram helps!

There is one relay that controls fan operation in case the coolant gets too high.

One relay controls fan operation when the AC compressor is operating.

The last relay as I remember allows the fans to run at high or low speed. High speed is when the fans are wired in parallel, low speed the fans are wired in series.

There is a coolant temp sensor on the bottom of the radiator to turn the fans on/off if the coolant temp goes over say 200F (Can't remember the exact number but there is one).

The fan system will turn on IF the plug to this sensor is disconnected. This is because when the coolant relay turns off (power to its solenoid coil is removed) the fans turn on. This is opposite of what one would expect. Perhaps the wiring is not correct or a wire is disconnected.

One way to check correct operation of the fans is to remove the electrical plug from the radiator coolant sensor with the ign switch on, the fans should turn on.

Typically the issue is with the first relay, the sensor on the relay or the wiring.

There is another coolant temp sensor that connects to the temp gauge in the dashboard. This sensor is mounted on the large coolant output manifold bolted to the head. The sensor only operates the temp gauge. You may be referring to this sensor in the issue about the temp gauge moving when the wiring/sensor was moved.

There is one more temp sensor on this manifold that tells the engine computer what the coolant temp is. This is to help the computer set the air/fuel ratio, etc.

The temp gauge system on the dash is completely separate from the system monitoring the coolant temp to turn the fans on and off.

One major overheat can be enough to cause head gasket failure.

A compression test can indicate a blown head gasket if bad enough. Ideally two adjacent cylinders will have low compression when compared to the others. If the compression is low enough the problem can show up in the engines performance.

However compression can appear to be within normal in all cylinders or not that abnormal (no smoking gun) yet the head gasket have a slight leak.

The block test will indicate if there is a exhaust gas leak where the compression test is inconclusive.

Exhaust gases in the coolant system can cause overheating and overflow tanking boiling. Plus other strange overheating issues.

If the radiator was tested on a machine would assume it is OK.

In the link sent about overheating there were other possibilities such as a collapsed lower radiator hose. This does happen but does not seem to be common, yet still something to check.

I am not sure how much effect the coolant fans running constantly have on the coolant temp. Would be curious to determine what happens when they are turned off.

Unfortunately overheating when driving at hwy speeds is typical of a blown head gasket.

If sure the car did not have a head gasket problem one would start checking the items already replaced.

If the car overheated at idle or low MPH (stop and go) the fans could be the cause (this does happen often enough). The fans are not needed at hwy speeds and the engine would not overheat at hwy speeds even if the fans were not working.

The fans pull air over the radiator fins, there is enough airflow over the fins at higher MPH that the fans are not required to help out.

Water pump failure is very rare but does happen. The blades can break or some other rare issue. The pump was replaced.

The thermostat would be another logically place (common issue), the thermostat can stick or fail to open all the way. This was replaced.

A plugged radiator is possible and does happen, this was tested.

Lower coolant hose collapse is rare, the hose can be inspected when removed. If the radiator was removed for testing the hose "should" have been inspected.

Sometimes the coolant system gets plugged up with "junk," (reasonable common enough), a flush should remove all of this.

I suppose there are can be other issues such as the engine running to lean, etc or something I missed but the typical causes of overheating seem to be covered.

Ask you mechanic to run the block test, or buy the test kit and do it yourself, or give it to the mechanic to use. If the fluid changes color you can assume the head gasket has problems. This test may relieve your concerns.

The head may or may not be warped, but it does happen. Your mechanic can inspect for this if they have a straight edge (a long piece of straight rigid steel) and a set of feeler gauges. The process is straight forward and easy enough. They could also do a an visual inspection for cracks.

Head cracking is rare, I think a machine shop charges $50-100 to do a pressure test for leaks.

The issue is again much of the work being done is labor. IF the head is warped enough the replacement head gasket can just blow again. Checking for a warped head is cheap insurance against having to do the job all over again.

Checking for cracks may be optional but I have this done as I don't want to do the job over again if there is a problem and my labor is free.

As to the block test, if you are going to spend $1K a few dollars more on this test is good investment.

 

the only way to test a radiator is the old fashion way........warm up the car and when the temp gauge reads normal, shut off the engine. now place your hand on the radiator fins, starting from the top corner and working your way across the top. then slowly slide you hand down........notice the warmth of the radiator. if you come across a cold spot........you have a blockage that cannot and will not be cleaned out by flushing.............you'll need a new radiator.

now, you say the water pump is new...........but where was it bought from........a toyota dealer or the local parts store.........?? was it bought new or rebuilt...??? you still could very well have an air lock in the system.

what i used to do in these situations was, jack up the front end of the car, and put it on the highest setting you can on those stands...........

now, open up the radiator, and start up the car............turn on the defroster so this way, the heater core will get circulation as well.........

leave the radiator cap off, and if possible, idle the car at a fast idle, say around 1,000 rpm's.........watch the radiator for circulation., as the water level drops, add more coolant of the proper mix........slowly but surely, the air bubble (lock) will come out...........

the reason why you need to jack up the front end is that at level ground, that air bubble will stay put, but like anything else, it will go to the highest point, sooner or later...........

and those fans should NOT be on all the time, only when the temp switch turns them on, or when the a/c is on.............