92 Legacy wagon overheating while idling

[Gnuman]

OK, I only have a few symptoms on this one. I was in the process of rescuing a Toyota on the freeway (alt went out, and I had to get the car off the freeway, so I charged the battery with jumpers of my system) As I was idling there on the side of the freeway, my temp guage started climbing. I opened the windows and hit the heater to max and max fan (this always brings down the temp). By the time I got around to checking under the hood the rad fans were not going (and when I checked inside,the temp was normal).

the symptoms are :

high reading on the temp guage

no CEL

hot day

Idling for extended period of time (I charged her battery for a half hour to get her safely to my parts place, where the electrical system could be checked)

when heater engaged, temp went to normal

did not see any fan activity

 

The above is the main part of this thread. What follows is what I plan to do soon anyway.

 

I will be watching this for the next few days to be sure the fans are engaging. That is the only thing I can think of that would cause this. It does not overheat at all when I'm driving. On second thought, could this be an indication that the WP is starting to go? I'm saving up for parts to do a heavy maint at 180K miles, including the WP, Timing Belt, and most of the seals. Will probably pull the engine as I will need to replace the rear crank seal (I know that one is bad). Debating with my bank account wether to put in new HGs as well, as a preventitive measure. . .

 

Timing belt would include TB, WP, OP (seals, O-ring, back out the screws on the backing plate, and torque them with good threadlock), probably new cam seals. . .

 

If I pull the engine to do the job, I would replace the HG's, intake manifold gaskets, rear crank seal, crossover pipe seals, cam cover seals and o-rings, cam cover gromets (for the bolts), and everything listed in the timing belt service. I call the latter "all soft parts". This car has given me excelent service (far beyond anything I ever expected), and deserves the pampering of the latter service. . . Now if only I can convince my bank account of that. . .

[1 Lucky Texan]

You should be able to confirm the fan cycles in 15 minutes or less idling in the driveway. I'd suspect the fan or its controller or a partially clogged radiator - but do investigate it properly.

 

good luck (good thinking on the heater fan too.)

 

Carl

[Setright]

Yeah, the fan is going haywire or maybe the thermostatically controlled switch that activates. It should have one plugged into the radiator.

 

Removing the engine will aid your work - and keep your back straight! - but removing the exhaust stud bolts from the heads will probably be a real pain in the you-know-what. Soak in WD-40 24hrs ahead if possible.

 

I would fear that at least one exhaust stud will break or take the threads out the head in the process. Therefore, HG replacement would be a good idea, 'cause you'll need to send the heads for machining of threads/studs on the exhaust ports....along with the cylinder mating surface.

 

It's an EJ22 right? It's worth the work! I still miss mine

[Gnuman]

Yeah, the fan is going haywire or maybe the thermostatically controlled switch that activates. It should have one plugged into the radiator.

 

Removing the engine will aid your work - and keep your back straight! - but removing the exhaust stud bolts from the heads will probably be a real pain in the you-know-what. Soak in WD-40 24hrs ahead if possible.

 

I would fear that at least one exhaust stud will break or take the threads out the head in the process. Therefore, HG replacement would be a good idea, 'cause you'll need to send the heads for machining of threads/studs on the exhaust ports....along with the cylinder mating surface.

 

It's an EJ22 right? It's worth the work! I still miss mine

 

Update: the overheat was totally isolated, and I have not been able to reproduce it. I've also had the headers off recently and there is no problem with any of the studs, so that is all good. I'll be taking the engine down to bolts when she reaches 200K, just to check things out inside and be sure there is no untoward wear. I'll probably post a new thread at that time (likely to crow about how nice the engine is on the inside ).

[tunered]

one of the fans should come on if you hit the air cond.

[Gnuman]

one of the fans should come on if you hit the air cond.

Both do, and they stay on. Also the fans are working correctly, as I verified later. This may have been an isolated glitch.

[tunered]

if that car is a female maybe its one of them hot flash things.

[Gnuman]

if that car is a female maybe its one of them hot flash things.

Those are not hot flashes, they are POWER SURGES. . .

[Gnuman]

Bump and update with a few guesses:

It happened again yesterday, the temp guage went to just below redline. I popped the hood and the fans were not running! Looking back, i would guess that if the alt was going, I would have been in a low voltage situation each time. I had the alt tested a while ago, and it showed 40A to the battery, with the A/C, and headlights off. With the A/C on, it showed near 0A. I'm guessing that the alt is weak (on the way out), and the times that the car overheats is when the voltage is low, giving one of two causes: 1) with the low voltage, the temp guage to the ECU does not have the range to show an overheat. 2) the ECU tries to turn on the fans, but there would not be enough power left over so it leaves them off (yeah, this is a long shot in the dark). Aside from that, perhaps the temp sender to the ECU is bad, or maybe the one to the guage. Should probably replace both to be sure. Along with the alt. Am I nuts to suspect the alternator as the cause of my various problems on the car?

the overheating is one. I also have problems with the CD player skipping badly. I'm thinking that there is simply not enough juice to run it right (power is dropping out, but that is annother thread)

[nipper]

replace the temp switch that turns on the fans . Its a reeasonable to come up with. Your over thinking the problem. Also i would have the charging system checked again using one of those big metal boxes (battery load test) with the jumper cables. That will test the battery/starter/altenator. AT idle an altnator wont put out much power, if any, you have to rev the engine a bit to have it make power.

If you notice in really heavy traffic on a summer day (read road closed traffic not moving for hrs) cars , newer cars with popped hoods. This is because they sat there ideling for hours never reving the engine every so often tocharge the battery. With all the gizmos in the new cars, they ran down the batteries. This is rare but ti takes a long time to do. Usually thses are higher end vehicals with all the widgets.

 

nipper

[Legacy777]

Get your power issues taken care of and see if that affects your temp issues.

[OB99W]

It happened again yesterday, the temp guage went to just below redline. I popped the hood and the fans were not running! Looking back, i would guess that if the alt was going, I would have been in a low voltage situation each time. I had the alt tested a while ago, and it showed 40A to the battery, with the A/C, and headlights off. With the A/C on, it showed near 0A. I'm guessing that the alt is weak[...]Am I nuts to suspect the alternator as the cause of my various problems on the car?

Low electrical system voltage can cause lots of seemingly unrelated problems. I'm not sure whether this particular problem one is of them; a bad fan thermostat could certainly be the cause.

 

Although a bad diode or regulator could limit output, I suspect that the low current when your A/C is on might have less to do with the alternator and more to do with what's driving it. From an electrical standpoint, the additional load of the compressor clutch and blower fan could cause a marginal alternator drive belt to slip. Make sure that it's in good shape and tight enough.

 

From a mechanical aspect, the thing to consider is that engine RPMs will drop when loaded by the A/C. What Nipper said about alternator output should be kept in mind. Particularly at idle, a small drop in rotor shaft speed can make the difference between charging or not. Charge current can only flow from the alternator when its output voltage is higher than that of the battery. A small drop in engine RPM can bring the alternator speed below that threshold, even without an alternator defect.

 

Interestingly, a "higher" output alternator won't necessarily assure you of more available current at low speed. In fact, just the opposite is often the case, and the "lower" output unit might produce more below a certain RPM.

 

As has already been suggested, having the charging system and battery checked is probably a good idea. A decent shop will put an oscilloscope on the battery terminals with the engine running and look for uneven ripple, etc, from the alternator, which could indicate a bad diode or brush/slip-ring problems. An alternator output test done on a bench would allow the output versus speed to be checked.

 

--OB99W

[Gnuman]

Low electrical system voltage can cause lots of seemingly unrelated problems. I'm not sure whether this particular problem one is of them; a bad fan thermostat could certainly be the cause.

 

Although a bad diode or regulator could limit output, I suspect that the low current when your A/C is on might have less to do with the alternator and more to do with what's driving it. From an electrical standpoint, the additional load of the compressor clutch and blower fan could cause a marginal alternator drive belt to slip. Make sure that it's in good shape and tight enough.

 

From a mechanical aspect, the thing to consider is that engine RPMs will drop when loaded by the A/C. What Nipper said about alternator output should be kept in mind. Particularly at idle, a small drop in rotor shaft speed can make the difference between charging or not. Charge current can only flow from the alternator when its output voltage is higher than that of the battery. A small drop in engine RPM can bring the alternator speed below that threshold, even without an alternator defect.

 

Interestingly, a "higher" output alternator won't necessarily assure you of more available current at low speed. In fact, just the opposite is often the case, and the "lower" output unit might produce more below a certain RPM.

 

As has already been suggested, having the charging system and battery checked is probably a good idea. A decent shop will put an oscilloscope on the battery terminals with the engine running and look for uneven ripple, etc, from the alternator, which could indicate a bad diode or brush/slip-ring problems. An alternator output test done on a bench would allow the output versus speed to be checked.

 

--OB99W

 

OK, first off the alt is not on the same belt as the A/C, and the testing was done at 2K RPM. Belt tension was OK (no slipping at all), so that leaves low output. I'm a bit concerned that the A/C draws close to 40A, but that is something I'll have to deal with later. My car has almost all of the widgets: Good stereo, PW, PS, PB, AC, PDL, PM. . . My headlights stay on. Of those, only the AC, and maybe the PW would be an issue for draining the battery while driving. The brakes and steering are driven by the engine , not the battery, and are always there, so the ECU compensates for them at or near idle. Perhaps the stereo, but I do not see that as very much of a drain (it is an OEM stereo, and only 4x20W at that. Now if I kept it turned up to max. . . But I don't.) So I see the alternator putting out sub-par current as the most reasonable solution. My guess is that it contributes to the overheating by letting the battery discharge to the point that the reference voltage changes to the point that the ECU does not know it is overheating.

[Legacy777]

Or the low voltage isn't enough to engage the relays.

[OB99W]

OK, first off the alt is not on the same belt as the A/C, and the testing was done at 2K RPM. Belt tension was OK (no slipping at all), so that leaves low output. I'm a bit concerned that the A/C draws close to 40A, but that is something I'll have to deal with later. [...] So I see the alternator putting out sub-par current as the most reasonable solution. My guess is that it contributes to the overheating by letting the battery discharge to the point that the reference voltage changes to the point that the ECU does not know it is overheating.

Hmmm, I didn't say that the alt and A/C are driven from the same belt, although I did suggest that they both were driven by and load the engine. That the test was run at 2,000 RPM doesn't indicate much about what happens when the fan problem is occuring at idle, which is what you've been saying.

 

I don't know why you're assuming that because the alt output dropped very low when the A/C was turned on that the A/C is drawing nearly 40A; current doesn't get "depleted" that way.

 

Rather than get into a long-winded explanation of Ohm's Law, etc., lets go back to the suggestion that you get your alt/bat/etc checked in addition to the rad fan controls.

 

By the way, if you have a decent voltmeter you can do a quick check of your "low voltage" theory. A "12 volt" lead-acid battery is actually a series connection of six cells that when fully charged should be at about 2.1 volts each, for 12.6 volts at the terminals (if the battery has been recently charged, a slight "surface charge" may bring it above that, but running accessories for a few minutes with the engine off should bring it down to 12.6). After a short warmup, at idle the voltage across the battery terminals should be at least 13.5 volts if the alternator is functional. At higher RPMs and dependent on temperature and other factors, the voltage is often in the 13.8 - 14.8 volt range. If you don't see voltages around those, the charging system is suspect.

 

The battery acts as both a storage device and a filter for the electrical system. It supplies current when the alternator can't make enough, especially at idle. Something as simple as a bad cable connection can prevent it being properly charged, delivering "make-up" current, and smoothing out alternator ripple and other voltage variations. Sometimes a connection that looks good can be resistive. Checking for a voltage drop from the battery post to the terminal (both positive and negative), especially under load, can detect that.

 

Best of luck.

 

--OB99W

[OB99W]

For anyone interested, I just found some decent info about the charging system at End Wrench: http://endwrench.com/images/pdfs/BatteryAltWin03.pdf

 

--OB99W