2005 S40 intermittent overheating
 

FIrst hello what a cool site resource. As you can see from the title car is giving me a hard time. Recently I changed water pump, timing belt, resevoir and cap (OEM) also thermostat and housing and sending unit and all the hoses except the 2 that go into the firewall. There is a long story to all of that it has been a what is next kind of repair. But the new issue is the overheating car will run right in the middle no issue and than temperature takes off. I have been tossing a.c. on to bring temp back to center but not every time I drive it. Fan seems to work and than not work without the a.c. on? I am still chasing a very small leak at resevoir and am curious if it is that simple would like some advice before a buy a fan assembly for no reason. Thanks in advance today I have ran the car twice and it has stayed dead center.

The engine computer will turn off the AC if the engine gets too hot. You have what sounds like a blown head gasket. Which engine is in your S40?

I have the 2.4 a little confused I turn the a.c. on if it starts to overheat and this brings temp back to normal. I have no power loss no water in oil no smoke. I know that doesn't mean I don't have a head gasket problem.

It doesn't sound like you have a fan problem. I will assume that you plugged the sensor back in on the thermostat housing.

When you fill that engine with coolant, after it runs a while you will need to add another quart or so to top it off. I assume that you've done all of that and still have overheating issues.

With good water circulation, the only thing that comes to mind is that the system is getting over pressurized from a failed head gasket. Maybe you should give us the history of what led to the mass parts change?

So I have had the car since December it has 135000 miles on it. One morning driving to work it just died. Called Triple A towed it to my dad's and put it in the shop. Noticed the reservoir wss almost ampty. I was almost positive it was correct prior to that morning. Filled it car fired right up sounded fine. Than i noticed a leak at tge water pump. So that led to timing belt,water pump and a.c. belt. Pretty straight forward repair. As soon as I fired it back up and it got to temperature I noticed the reservoir was cracked on top. So ordered tank and cap. As soon as that was changed noticed a leak at the plastic section of hose by thermostat. So ordered hoses. In the process of changing hoses we checked the thermostat and the housing looked a little rough so ordered the thermostat and the housing and the sensor. So finally get all that done and than for the first time it overheated. That is when I found out after market resevoir and cap had a bad rep do ordered OEM. That gets us to current situation. Sorry for the length but that is the story. Really like the car and still haven't spent as much money as a shop would of charged to just do water pump. Not afraid to bust knuckles just looking for some trouble shooting help. Thanks again

That was a good explanation. Thank you.

I suspect that you have a blown head gasket due to low coolant the first time around. The 2.4 is a simple engine to work on and I just finished a 2.4 T that we sold at our dealership. In that case, we didn't have overheating issues but I noticed some coolant on the oil cap and the crankcase breather was full of sludge. We pulled the cylinder head, had it flattened, installed new valve seals, had the oil pan removed and cleaned and finally, installed a new crankcase breather box.

I think that you need to do the same repair that I did. That's my suggestion from your story.

I greatly appreciate your input. What is the best way to test for the head gasket? Thanks to forums and YouTube there aren't to many projects that are to big for guys and gals with some common sense.

There are several tests that I am aware based upon the head gasket leakage. Here they are:

Head Gasket Leaking in Oil - you can usually find some light-colored residue on the oil cap since the water in the coolant gets heated and turns to steam in the hot oil. A small leak will give a telltale sign like that. Of course, a major leak will turn the oil into a milkshake.

Head Gasket Leaking in Coolant - with the engine running, the system will become overpressurized since the system is designed for 16 PSI and the compression runs a lot higher. As the engine cools down, the coolant will go back into the cylinder and can create a momentary misfire at startup. The spark plug on that cylinder will also likely have some type of white residue from the coolant.

Head Gasket Leaking to Another Cylinder - Basically you will find this in a compression test by having low compression on two adjacent cylinders.

Despite best efforts, it is often a rule-out methodology. In the case of the 2.4 T that I tore down, I had a trace on the oil cap and the car was a bit low on coolant, although no overheating. When I tore it down, it appeared that the head gasket had deteriorated between the cooling jacket and the oil return in the block.

I will change oil tomorrow and let you know.

If turning on the A/C brings the temperature down, that tells me that there IS a fan problem (since all other things being equal, turning on the A/C will increase the load on the engine, and will shed heat into the radiator, both things that could cause the temperature to go up if it wasn't for the fact the fans are forced on any time the A/C is running).

I haven't gotten my manual yet, but normally the fan circuit is pretty straight-forward. When the temperature gets to a certain level, the fans come on. If you had a Vida / Dice system, or maybe a Bluetooth OBD system like Torque Pro or similar, you could read the reported coolant temperature.

It's also possible that there is some air trapped in the system (common when doing a total drain-and-fill). I'm not sure if there's a bleed valve, but brining the engine up to normal temperature with the heat on high, and with the coolant reservoir cap off or loose, and topping the tank off a time or two as necessary will normally get it done..

My thoughts were that with the fan running when he turned the AC on says that the fan works. I did ask if he plugged in the sensor for the coolant temperature and reminded him to check all of that again.

Without being there to test the car, I would agree that checking for codes is the way to go. However, it doesn't sound like he has access to that so we have to go another direction.

If the ECM is not able to regulate the fan for engine temperature, I assigned a low probability that it would work on the AC circuit from line pressure. However, all of this is based upon my experiences. Whenever I have a vehicle acting like this I suspect a head gasket issue.

If the car overheats and the fans aren't running, and turning on the A/C causes the fans to come on AND the temperature to drop back to normal, then we know three things...

1) there is a problem with the thermostatic fan switch (or ECU controlling the fans) that is causing them to not engage at the proper temperature, and...
2) the fans themselves are fine, and...
3) the engine should run at normal temperature once the fans are coming on when they should.

If I've mis-read the OP's comments and my assumptions aren't correct, then I could certainly be wrong. The way he worded the use of the A/C to bring the temperature down is a little ambiguous, so there could be other things in play.

This is a tough thread because the car was previously worked on and quit running. All of this is "fill in the blank" since we've not seen the car.

Until we get more information, we are only guessing from experience.

Nice to see some back and forth troubleshooting done with respect. But to maybe answer a couple questions my stating I turn a.c. to bring to normal temp is said because my understanding is turning on a.c. forces fan to come on. Than car runs in the middle where it belongs. Also found nothing in oil today. I had a similar experience with a pt cruiser that had a fan issue. I am finishing a flush today so hopefully I can keep the air out of system because I don't think i have a bleed valve.

I would suggest that you get a scan tool and see if you can monitor engine temperature. The ECU is dependent upon cooling temperature to command it on or on as a percentage. The later cars use a modulated pulse width signal to vary the fan speed. With a scan tool you can command the fan on and also watch the ECU control the fan speed.

Keep in mind that the engine fan won't come on until you get about 205 degrees and then it will come on at a speed that the ECU finds appropriate.

Tony thank you
 

So wanted to update the problem was head related. Didn't make sense based on my history with other vehicles having same issue. But in the end after testing for exhaust gases in coolant it was made quite clear. So a big thank you for the help.