I blew a head gasket once years ago and the oil and the antifreeze were both a mess. It also ran hot even without the AC on. Brown sounds like the radiator has rusted internally and may be partially blocked. This would explain why it only runs hot with the extra AC load. I don’t think over tightening the belt would cause it at all. A belt too loose on the water pump might though. There are tests a mechanic can do to determine if the head gasket is leaking. Is this a mechanic that has done reliable work for you in the past? Might be a good time for a second opinion. Ask friends for a good recommendation first, not a dealer and not a chain like Pep Boys.
Here is an update. First, thanks to everyone who contributed ideas. Now for what’s new in my little mystery.
I found the leak responsible for the creamy mess shown in the photographs. It was a pinhole leak in a 1/2" O.D. hose coming off the rear of the engine (this is the 6-cylinder). The leak only occurred when conditions were just right. And surprisingly, they were just right at the moment I pulled into the dealer for service! I had been hunting for the leak for a couple weeks with no success. But when I popped the hood at the dealer there was a tiny little geyser erupting from the back of the engine compartment.
So, that part of the mystery has been solved, it turns out I didn’t blow a head gasket, and the fluids are all normal - no oil in the coolant and no coolant in the oil.
However, I’m still overheating under some conditions and I either need to get this fixed or get rid of the car - and that’s a big financial problem.
The overheating does not occur completely predictably. However, as far as I can tell, it is triggered by load and time. For instance…
Tonight I drove home from work. The outdoor temperature was 95 degrees and humidity was 80% or so - typical Boston mid-summer weather. I drove 1 mile on a local road and then entered the highway where I drove at 60 MPH or higher (OK, sometimes a lot higher) for 20 minutes or so. I then entered stop-and-go traffic that lasted 10-12 minutes. Then I got back up to cruising speed. So now I’ve been driving at high speed for 20 minutes plus stop-and-go for 10-12 and then back to full speed for 3-5 minutes. Yet. only now does the temperature gauge start to climb above normal (normal for my Accord is about 40% up the gauge).
Once the temp started tonight rising it just kept on climbing. It didn’t rise fast, but it rose steadily. About 5 minutes after it started to rise it reached 75% or so on the gauge. I turned off the AC and the temp started going back down within seconds. It steadily dropped but, interestingly, only got down to just under half-way on the gauge. It didn’t go all the way back down to its normal 40% mark.
I drove the rest of the way home with the windows open and sweat running down my back.
Once I got to my town my speed dropped to 35. I turned on the AC and noticed the temp start to climb right away. Naturally, I turned it back off and again it dropped back down. More sweating followed.
As you can see, the problem doesn’t just happen because the car has been running long enough, got warm enough or is going fast enough or stuck in traffic. Tonight I went over 30 minutes of high speed and bumper-to-bumper driving without any symptoms. And then suddenly the temp started rising.
Once the temp rises the first time during a drive it doesn’t un-happen, the temp never gets all the way back down to my car’s normal level. And, even when I get down to low speeds I still cannot use the AC without the car starting to overheat. Yet, sometimes I can drive around and do errands for a couple hours with no problem at all.
I have had the leak fixed. I had the cooling system flushed. All the fans are working as far as I can tell (I’ve pulled over and checked on numerous occasions and both fans are always running). The coolant is the proper mix and checks out on a coolant tester. And oh yes, the AC works ok - not super cool but good enough to satisfy me.
So, can anyone help out or suggest a diagnostic approach? I’m a pretty good mechanic and a very good diagnostician but I’m stumped, stumped, stumped.
Again, thanks for the help people have offered.
[b]The mechanic thinks that means the head gasket is gone and oil is getting into the coolant. But I always thought a blown head gasket lets coolant get into the oil.
Is he LIKELY to be right about this? [/b]
He may be, but he needs to test it before pulling the heads. Was there oil in the coolant or coolant in the oil? Looking brown can jest mean minimal rust.
It’s time to take it to the pros now: a radiator/ ac repair shop. You didn’t change the radiator cap. You probably didn’t use a chemical in the cooling system flush to remove mineral buildup, or check the water pump flow rate, or pressure check the coolant system. Is the thermostat allowing adequate flow? With a system this old, the next hose to go will be the upper radiator hose, followed by one of the other hoses. If this is a Accord EX, the hoses, on the back of the engine to the oil cooler (under the oil filter) won’t last forever.
Hey, I have a '99 Acura 3.2 TL with the EXACT SAME PROBLEM. As a matter of fact, I took my car to get all cleaned up today in preps to sell it this weekend to CarMax. I’ve been experiencing the same problem for a year now and no one could ever tell me what was wrong. I took it back to Acura (4th time) a month ago and was told I have a blown head gasket. I honestly wouldn’t recommend driving it if it’s overheating b/c you can really mess the car up. I took it out today for the 1st time in a month to test the conditions under which it would overheat. Because I only have this problem in the summer when the Georgia heat is oppressive I had to wait until it cooled off some. This is the 1st weekend that we’ve had moderate temps (80) so I figured it wouldn’t overheat today. It was running just fine until I turned the A/C on. The second I turn it off, the temp needle comes right back down within minutes and doesn’t overheat anymore. So it got me to thinking that if the head gasket were truly blown that it should overheat under all conditions. I’m no mechanic so I could very well be wrong but I came to the conclusion that at the very least, I will get a second opinion this weekend before I go purchase another car. I did take it to the guy that usually services my family’s cars and he suggested last year that it could be the expansion valve. This would make sense b/c he couldn’t find any leaks anywhere and he said if the pressure builds up too much then that will cause overheating. I’ll check into that this weekend to see if that could truly be it. Of course, when you have an undiagnosed problem you run the risk of then blowing the head gasket if you keep driving around. So it may truly be gone but I’m still not 100% convinced just yet. I have a brand new thermostat, thermostat gasket, alternator, and both fans are running (condensor fan almost new). All fluid levels are fine as well as the radiator. I have no idea what else could be wrong. Does anyone have ANY thoughts on the expansion valve suggestion? Or should I look at a new radiator cap? You’d be helping both the original poster and me. Thanks!
I would be a bit dubious about the diagnosis of an expansion valve causing your overheating. The expanion valve is part of the A/C system and if the valve was sticking closed then it’s possible the AC high side pressure would climb and the engine would overheat.
This also means the AC would quit cooling and a pressure switch should cut the compressor off.
If this overheating with the AC on occurs during in-town driving then I would suspect a clogged radiator, just like the OP.
A head gasket will not cause overheating unless the gasket is allowing a coolant loss, the cooling system is being pressured up by combustion chamber gas, or a head gasket is blown between 2 cylinders leading to loss of power and engine strain.
This will not be a now and then thing; it will occur every time.
Testing for a head gasket problem is verifiable with a compression test, vacuum gauge, cooling system pressure test, and hydrocarbon test; preferably using all of them.
Testing for an expansion valve problem is done with a full gauge set. No guess work there.
After your car has sat all night and is cold, loosen the radiator cap to release any pressure. If you hear a hiss the you likely do not have a head gasket problem.
Retighten the cap, start the engine and allow it to idle for about 30 seconds. Shut the engine off and quickly release the radiator cap. If you do not hear a hiss then again, you likely do not have a head gasket problem.
Hope some of that helps.
$12.95 for a new radiator cap, its a no brainer, get one. 10 years old, its due anyway.
Since the coolant stayed in the system long enough to turn brown, I’d say that you may still have some blockage issues somewhere in the system and/or your water pump is marginal. When you run the AC, it heats up the air going to the radiator, so if the cooling system is marginal, the system temperature could start rising. Once it starts rising, it can be difficult to get it to come back down.
I am not a fan of chemical cleaners, I think they do more harm than good, and I’m not a fan of flushing the cooling system unless there is a problem, and you have a problem. If the new radiator cap does not fix your problem, then I’d look into some type of mechanical flush. I would remove the radiator and flush it out on the lawn with a garden hose. Then I’d remove the thermostat and flush out the engine with a garden hose. If you are due for a timing belt, then I’d suggest getting a new waterpump at the same time. If you do all this, then you might as well put in a new thermostat to head off a future problem, though I doubt the current one is bad.
If you do all the above and your a little casual on your cooling system maintenance schedule, then I’d also recommend that you finish off with a fill of one of the new HOAT antifreezes mixed at 2:1 with distilled water. You get some extra corrosion protection that way.
I agree with you that the expansion valve should not cause the overheating. Our 97 Accord had what I believe was a stuck expansion valve last year. It decreases the effectiveness of the AC system but the cooling system never overheated. I only have the 4 cylinder and have giving thee cooling system what I consider reasonable maintenance.
I say suspected expansion valve because when the AC was not cooling as much as it should (60? vent air vs 40?), the high side pressure was high and the low side low. Somehow it fixed itself. Its been good all this summer.