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Old 7 Sep 2005, 18:57 (Ref:1401589)   #1
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Diagnosing a damaged cylinder head gasket

My car has been suffering from overheating under high load. I suspect that it might be an electrical problem, particularly with the fan as I think that instead of engaging second speed it might be shutting down. However, my mechanic believes that the cause could be a "burned" cylinder head hasket. However I wouldn't like to dimount half the engine just to find that it was OK so he told me that there are a couple of ways to tell if there's any damage. First is to open the expansion bottle when the engine is cold (preferably during the mornings) and see if there's any air going in or out (like when one opens a soda bottle). Number 2 to check for traces of moisture on the oil cap. I've done both but both tests have yielded no indications of a bad gasket.

Is there anything else that I could do diagnose it?
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Old 7 Sep 2005, 20:03 (Ref:1401637)   #2
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Is there anything else that I could do diagnose it?
Lots of things:

The thermostat could be frozen partialy closed. With a thermometer, verify the temperature on a metal part of the radiator housing. This will also give you an indication of the effectiveness of the fan control switch as you can observe the temperture rise to the operating point(s) for the fan(s). Check a service manual. Usual range is 110-125° C. The top of the radiator will be the warmest, the bottom will be the coolest. The sensor is usually placed near the bottom of the radiator. When (if) the thermostat opens, the temperature should decrease by at least 10° C within a few minutes. If not, spray cold water from a hose on the front of the radiator (careful not to flood anything in the engine compartment).

The timing could be retarded or the spark plugs could be deteriorated so as to provide late/difficult ignition.

Fuel mixture could be too lean under load. You didn't state if your car was injected or carburetted.

The radiator could have minimal fluid flow - clogged tubes. Turn the heater on to it's warmest setting w/high fan speed and see if it stabilizes the temperature.

The water pump could be worn out (impeller not efffective or cavitating)

A blown headgasket has to `blow' something somewhere. One place would be coolant into the oil supply. This is indicated by `milky' or `grey' colored oil on the dipstick as well as the filler cap as you have noted.

The other possibility would be combustion gasses escaping into the coolant. This can be identified by very carefully using a rag or some other method, remove the radiator cap (not the cap on the catch bottle) while the engine is idling. Slowly increase the revs and look for bubbles in the coolant. If you have them, it is either water pump or head gasket. Opening the catch bottle will never produce any sound as the system is not sealed at that point. The sealing is done at the radiator cap which incorporates a pressure relief system to vent into the bottle and siphon back when cooled.

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Old 7 Sep 2005, 21:30 (Ref:1401675)   #3
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The car is injected and I changed spark plugs about a year ago but I already had the overheating before that. Likewise, the injectors were cleaned when the sparkplugs were changed. Did an exhaust gas test a couple of months ago and everything seemed to be OK. The radiator was fixed and unclogged a couple of months ago as well.

This is what happens. the car is small engined (1.1L) so you have to force it a bit, particularly when going uphill. About a month ago I was traveling on an uphill road (somewhat steep) with a full passenger load. When I was doing between 65-75 kmph in third gird with high revs and full throttle nothing happened. But as soon as I drove into traffic and had to slow down to 45-50Kmph (second gear, full throttle and high revs again) the overheating light would come on within a couple of minutes. This happened about 3 times during the 1 hour uphill drive. The first time I pulled over and turned off the car. I heard the cooling fan at full speed and it stayed that way for about 5 minutes or so before shutting down or going into low speed. However, the second time it happened I pulled over, turned off the car but as soon as I turned it off I noticed that there was no noise coming from the fan (BTW, my car is one of those in which the fan works independently of the ignition switch). As soon as I got down I heard it starting. That was certainly not normal as the car was supposed to be overheating. The last time it overheated I could hear the fan (or so I reckoned) but it stayed on for quite a while. As a matter of fact, I could touch the radiator, feel that it was cool (cooler than under normal operation) but the fan was still going at full speed.

So my conclusion was: the fan switch is damaged. Instead of going into second speed as it should it's shutting down completely. This made sense as I had no overheating problems when I was doing relatively high speeds, and therefore had more air flow to the radiator than when I was doing slower speeds with the same load. But we ran several tests on the switch with my mechanic and it seemed to be working fine. Which brings me to possible cause #2.

Some months back (before replacing the battery) I had a number of electrical problems. The main problem was that I couldn't turn on the car when "medium/high power" electrical devices (lights and cooling fan in particular) were on. I would turn the key and nothing would happen. The car wouldn't even try to start (as it usually does with a dying battery). I couldn't even hear the starter motor doing anything. Replaced the battery (as the old one was over 5 years old anyway) and the problem apparently stopped. I could turn on the car even if the lights were on just as it should. However, during one of these overheating stops I tried to turn on the car while the fan was running at full speed and I got the problem again. I had to remove the cover from the stereo, turn off the lights and even remove my foot from the brake pedal to avoid turning on the brake lights in order to get it started (as the fan was still going at full speed).

So possible cause #2 could be that there's some kind of electrical problem. Namely, when there is already some kind of load on the electrical system (car running, lights on, etc), a high load condition (fan at full speed or starting the car) cannot be met so, for example, the car won't start or the fan won't go into full speed. Only removing the initial load (turning off the lights, the car, the stereo) would allow for this "high load" demand to be met.

But the strangest thing is that this overheating only happens when I'm on uphill roads at relatively low speeds. It NEVER happens with urban traffic. No matter how hot the day is or how bad the traffic jam is. It is only under constant high load conditions that this happens.

What could it be? I'm really frustrated.

BTW, the cooling fan only has 2 speeds. The highest, which is the one I mentioned, is never used under normal urban traffic. With regular use it just uses the lowest.

BTW, sorry for the long post but I wanted to describe the problem as accurately as possible. Any advise would be greatly appreciated
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Old 8 Sep 2005, 20:09 (Ref:1402228)   #4
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Definite looks like a `fan control' problem. However, the fan control might be coming from a `black box' (engine control module). The black box can retard the spark, lean out the mixture as well as direct the fan to run at high speed. If you have a bad water temperature sensor feeding the black box all sorts of `wrong' things can happen. I would asume that the fan does not turn on until the normal operating temperature is reached and then it cycles as needed (on-high-on-off). Do you have an actual teperature gage or a light that lights to indicate high tmperature?
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Old 8 Sep 2005, 22:31 (Ref:1402344)   #5
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The fan switch isn't connected to any black box. In fact, it is a "bolt" that is screwed to the radiator and has 3 electrical pins (I assume that one is always charged and the other two are for low or high speed). I had to replace it when I bought the car because it would get stuck and drain the battery. The circuit also hay a "relay" which is a small metal cylinder clamped to the top of the radiator.

Unfortunately I don't have a temp gauge on the dashboard and therefore have to rely on the warning lights. Although I'm pretty sure it was overheating because the engine compartment was very hot.
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Old 9 Sep 2005, 01:22 (Ref:1402434)   #6
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Quote:
Originally Posted by Sharky
The fan switch isn't connected to any black box. In fact, it is a "bolt" that is screwed to the radiator and has 3 electrical pins (I assume that one is always charged and the other two are for low or high speed). I had to replace it when I bought the car because it would get stuck and drain the battery. The circuit also hay a "relay" which is a small metal cylinder clamped to the top of the radiator.

Unfortunately I don't have a temp gauge on the dashboard and therefore have to rely on the warning lights. Although I'm pretty sure it was overheating because the engine compartment was very hot.
In a prior post you said:
Quote:
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BTW, the cooling fan only has 2 speeds. The highest, which is the one I mentioned, is never used under normal urban traffic. With regular use it just uses the lowest.
The most obvious solution is to force the "high speed" and see if in fact it is working. With the car parked and idling insert a piece of cardboard to cover the radiator (start with ~half, use something you can easilly remove if things get too hot too fast). Try and get a true thermometer (perhaps a probe type, used in cooking) and monitor the actual water temperature (remove the radiator cap) at which the fan operates/changes speed.

I would also question the function of the "The circuit also hay a "relay" which is a small metal cylinder clamped to the top of the radiator." If it is fastened to the to the top of the radiator it may have deteriorated due to heat or it may also have some type of temperature sensor. I think `we' are getting closer.
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Old 9 Sep 2005, 01:43 (Ref:1402438)   #7
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OK, I'll try that and I'll get back to you. Thanks

BTW, is there any kind of test I could do on the relay? I have a multimeter if that helps.....
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Old 9 Sep 2005, 01:57 (Ref:1402439)   #8
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Mhhh, wait a minute. I think we might have a problem because the fan is located in front of the radiator. In other words, it blows air instead of "sucking" it in. Will it work anyway if I just place the cardboard on the back of the radiator?
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Old 9 Sep 2005, 02:10 (Ref:1402443)   #9
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OK, I'll try that and I'll get back to you. Thanks

BTW, is there any kind of test I could do on the relay? I have a multimeter if that helps.....
It depends upon how may wires there are and if you can disconnect them easily. Remember that automobile electrical systems run 12v wiring that is always energized from the approprite fuse to whatever device is to be operated. The `switching' action that takes place in what you are calling your fan switch, for instance actually "Grounds" the circuit and completes it. Check voltage from ANY location to ground. There is NO `neutral' or `return' wire as you would find in your home wiring. Your three wire fan switch should have a wire that goes to a ground somewhere and two wires with a constant 12v. That means that it is possible that the wire for `high speed' is NOT energized at all, resulting in no high speed operation. The two wires with 12 volts probably connect to your `relay' somehow but what you are calling a `relay' might actually be the temperature sensor. Can you get a wiring schematic from your car dealer or is there one in in your owner's manual?
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Old 9 Sep 2005, 03:10 (Ref:1402460)   #10
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I just went down and took a couple of pictures (now that I have a digital camera ). Sorry for the dirt

This is the fan switch that is plugged into the radiator:

http://pwp.007mundo.com/chsoto/DSCF0538.JPG

And a couple of pictures of the "relay"

http://pwp.007mundo.com/chsoto/DSCF0535.JPG

http://pwp.007mundo.com/chsoto/DSCF0533.JPG

Also, here's a screenshot of a repair manual for this car which refers to this as relay:

http://pwp.007mundo.com/chsoto/manual.jpg

Thanks
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Old 9 Sep 2005, 15:19 (Ref:1402950)   #11
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The identified components are:

1. Fan, if it has two wires the only way to provide a slow speed is by dropping the voltage from 12 to 6 (?). If it has three wires, they are individualy energized to provide the two speeds via differnt windings in the fan motor. Wire colors are (?)

2. Temperature switch, three wires (green, blue white)

3. Relay, two wires (probably a temperature activated switch as it is on the hottest part of the radiator)

The pictures have changed my `overnight' thoughts.

I believe the `relay; also has an internal resistor (single speed two wire fan only). 12v from the battery goes to a fuse then to the relay, then to the fan, then to ground to complete the circuit. The resistor is in the circuit to drop the voltage to ~6v so you get 'slow' fan speed. When the temperature rises sufficiently, the `relay' will bypass the the resistor and allow the full 12v to run the fan at `high' speed.

The three wire temperature switch MAY prevent the fan from operating until the water temperature at the bottom of the radiator reaches 85-90° C. The bottom of the radiator is the coolest place and that is where the coolant returns to the water pump. Without tracing the wires I can not offer any other help.

I would determine the color of the wires, follow them if possible and search for the fuse that feeds the circuit. Then try and draw a schematic, noting wire colors and connections.

As the fan is not dependent on the ignition switch, using your multimeter with an aligator/crocodile clip on the black lead (-) fastened to a good ground and a common straight pin or safety pin on the red lead probe the appropriate wires to determine when various parts of the circuit are enregized and if there is in fact 6 or 12 volts present. Pushing the pin into the insulation will not cause any significant harm to the wires.

It is also possible that the ignition switch permits initial fan operation but one of the connections to the temperature switch will bypass the ignition switch to maintain power until the temperature drops to a safe level when the key removed from the ignition.

When checking across the terminals of components that are `switches', a "Zero" voltage indicates a `closed' switch, 6 or 12 volts indicated the switch is open. The voltage is truly named "Potential" as it CAN do work.

I wish that I was there `looking over your shoulder' but that is obviously impossible. My `instincts' point to the `resistor' (wherever it is located) as the cause of your other electrical trouble as well.

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Old 9 Sep 2005, 17:00 (Ref:1403045)   #12
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try a replacement radiator its more than likely blocked in the pipes inernally and no amount of cleaning will make it cool.
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Old 9 Sep 2005, 17:05 (Ref:1403053)   #13
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You've been very helpful, even if you're not right here.

I've been doing a couple of test and I think you're right. I unplugged the 3 wire connector that went into the fan switch and tested it with the multimeter. I got 12 volts when testing green-white and green-blue. Therefore green is always energized and white and blue are the ones that ground the circuit. Then I used a piece of wire to short circuit and found that green-blue is low speed and green-white is high speed. Then I unplugged the relay wires and plugged the multimeter instead. When I short circuited green and blue (low speed) I got 12 volts and got no volts when short circuiting green and white (high speed). Also, the blue wire goes into the relay and comes out as the white wire that goes into the fuse box while the white (high) goes directly into the fuse box from where, I would assume, it goes into the fan.

So indeed, as you suggested, the relay is nothing more than a resistance that reduces voltage to the fan when going into low speed.

But then I did this test. I short circuited green-white to get maximum fan speed (which I got). Then I started turning on every electrical device inside the car (Radio, heater, lights, braking lights, warning lights, etc.). As I started turning everything on I could hear the fan reducing its speed. Finally, when everything was on I tried to turn on the car and, as I suspected, nothing happened. Once again I couldn't even hear the starter moving (although everything inside the car was shut down as I turned the key, which is what any car does when it starts). tried again and it finally started.

Which brings me into this little detail. Since I bought the car over 5 years ago (I bought it second hand) I always noticed that the windshield wipers were somewhat "weak". They would always have a little "shake" when operating. Recently I had to replace the alternator's regulator and I noticed that as soon as it was replaced the wipers were opperating very strongly as they never did. But after a while they went back to their usual operation. I don't know if there's perhaps some kind of "power management device" that is failing and isn't sending enough power to certain devices.
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Old 9 Sep 2005, 23:13 (Ref:1403304)   #14
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You've been very helpful, even if you're not right here. I don't know if there's perhaps some kind of "power management device" that is failing and isn't sending enough power to certain devices.
Yes. The voltage regulator that is usually built into the alternator. However, it may be as simple as a loose alternator belt. It is possible for the belt to slip if it is not tight enough and the electrical load is high enough. This will result in lower voltage available to run things and you know what happens next. Check your service manual for the correct `slack' (~5mm) and see what yours is. It should be checked at the middle of the longest span of the belt.

With the car shut off, measure the voltage at the battery and try to find a connection method that will stay in place. Locate the meter where you can see it from inside the car and secure so that it does nor fall over when the car is started/running. It should be at least 13v and as much as 14.4v. Next, start the car with no accessories running and check again. Slowly increase the engine speed and see if the voltage goes up to ~15-16v. That is a sign of a healthy alternator/regulator. If not, have it evaluated by a specialist auto electric shop or just replace it. I think you have your answer.
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Old 13 Sep 2005, 00:47 (Ref:1406215)   #15
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¿El tiburón, dónde está usted? ¿Corre el automóvil bueno?

Mister shark, where are you? Is the car running ok?

Any of the `lurkers' out there have any comments on this exchange of messages? There are at least three of you.

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