Dear All,

this is my first time to post a message to this wonderful site. I have a problem that does need your help.

First of all, I am from Egypt which means normal temperature in day about 37 degree Celsius in summer. Sorry for not knowing the exact English words for the cars parts :(

I have a Skoda felicia 98 1.3L petrol engine equipped originally with A/C.

I had since two years ago.

one month ago, i had a problem which was an electrical short circuit in the fuse box which is inside the motor chamber not the one inside the salon. This short circuit led to a complete burn for the fuse box along with all the wires going to the fan and every electrical part in the motor.

I sent it to an authorized Skoda dealer in Egypt. He changed the whole electrical wires and the fuse box with new ones. He made other modifications to better suit Egypt's weather. As all of you might know, the fan in the A/C equipped felicia's has two speeds a low one and a high one. The high one should operate only if the A/C is working or if the car really overheats. He disabled the low one so if the water just heats a little bit -Above 80 degress- the thermostat closes making the fan work on the high speed directly instead of the low one.

Till now, the car is working pretty fine with no over heating at all AS LONG AS i don't turn on the A/C. The car sitting in the traffic in a very hot weather (above 45 celsius in the sun) never exceeds 84 degrees (BTW, he changed the thermostat (the one in the radiator) with a further lower temp one (82/68 degrees) so the car is really cold) this is good as the weather in Egypt is really hot like 9 or 10 months out of the whole year).

Let's go the problem, if i turn on the A/C (the fan directly works on the high speed) the car slightly overheats if the car is standing but if i go fast like over 80 Km/hr the car REALLY overheats that makes me to turn off the A/C. it reaches like 100 C and the fan is working and it continues to heat. This is very wierd because it is supposed to overheat when i stand (as no air flow goes to the radiator nor the cerepentine of the A/C) On the contrary, while standing rpm is below 10 the car is pretty cold (like 80) while going on in an empty road and speeding up the car really overheats.

Also, i noticed that when i really overspeed even without A/C (but we are talking now about over 130 Km/Hr) the car starts slightly to overheat but quite far from the case with the A/C turned on.

The car was pretty nice for two years before the electrical short circuit problem - I think that this problem is now totally solved - . I think that now the problem is with the engine power or sth like this.

I asked a lot of technicians (but not quite qualified) , the main suggestions i heard that the engine became weak that can't bare an A/C load neither a hard speed up and the solution is to replace a head gasket (apologize me if it is the not correct part but i mean the part in the engine that blows up if the car overheats and leads to that oil goes to water and turns to Mayonnaise like).

I doubt this because it is a hard conicidence that the car was pretty good just one month ago and then it goes totally weak.

Another suggestion i had that the part which controls the movement of the valves (i don't know its name but the one controled by the crankshaft) needs some adjustment as the fuel and exhuast timing are not corectly adjusted.

i am really in need for your help. Aplogize me for the bad technicall english spelling mistakes as i don't know the exact names in english.

Kindest Regards,

Mostafa

Does the temperature guage work correctly? Does it go up and down a lot?

My immediate thoughts are that the car might not actually be over-heating but perhaps the temperature sender is broken?

Another thought is that the radiator could be blocked.

If the fan is turning on with the A/C then it would suggest a coolant flow problem. If the mechanic changed then thermostat then perhaps you need to check it has been replaced by the correct part. The thermostat should come complete with the plastic housing and coolant temperature sender. if the old one was broken some of the plastic could have come off and clogged the system somewhere.

Hope this helps.

Glad I'm not living in that kind of heat!!

Phil

All good thoughts Phil. I'd head towards the sensor or the blocked radiator as the issues.

Mostafa, do you use "anti-freeze" in Egypt? I'm asking because a modern anti-freeze does much more than just lower the freezing point of the coolant. It contains a package of anti-corrosion additives which help keep the waterways in the engine, and the radiator matrix, clear and operating at peak flow, and also acts as a "water wetter", which actually raises the boiling point and heat transfer rates of the coolant.

Also, you've used all the correct technical words where you knew them, and are more understandable than some who would claim to be native English speakers. In your second last paragraph, the "part that controls the valve movement" is called a camshaft. This controls the valve movement in 3 ways:-

1) The valve timing, which is when they open and close relative to when the pistons reach the top of their travel. This isn't really adjustable on most production engines, and on the Felicia 1.3 adjusting it would require removing the oil sump anyway.

2) The valve lift, which is how far the valves open from their closed positions. This just plain isn't adjustable, short of fitting a new camshaft.

3) The tappet gaps, one for each inlet and exhaust valve. I've left this to last because the tappet gaps affect both the timing and the lift of the valves. Briefly, if a tappet gap is too wide, it reduces the valve duration (the total time the valve is open) and the peak lift; it also makes the engine sound rattly. If it's too tight it can make the duration too long, and even stop the valve closing fully, which effectively reduces the cylinder's compression ratio and hence the engine power. In extreme cases, it can even lead to the valve and/or its seat being melted by the combustion gas.

If it only overheats when the AC is on and not when the AC is off but the engine is been driven at high revs, I'd suggest that there is something causing the car to fail to cool properly when the AC is on.

An obvious one is to check the fans are operating. Another perhaps less obvious one is to check that the AC fan and the Coolant fan are both blowing air in the correct directions. No point one pulling and one pushing air as in that case you would get no air flow when they are both on and as such minimal cooling.

That makes some sort of sense; my biggest reservation is that it presumes the external air is significantly cooler than the engine bay air, and I'm not sure that would be the case in Egypt.

thanks all for your considerable and important thoughts.

@ Phil: I thought about radiator blocking problems but don't you think it is wierd that the car works properly without A/C and suddenly when the A/C works it turns to be blocked ?

Also, i changed the temprature sensor with an original one as it wasn't working correctly. Also when the car is overheated i slightly opened th cap and i found the water really hot (i know it is dangerous to be done but i make it with precautions :-))

I checked the thermostat but frankly speaking it is not an original one (as i said it is lower than normal) but it is correctly pluged in and the car again operates correctly without A/C

@Ken: the last trial i will make next weekend (in Egypt the mechanics have weekend on Sunday while other workers have their on Friday so i can go to my Mechanic on Friday (just Info :-))) is to replace the tape water which is bad one with green water (contains coolan) but i doubt it will make a great difference. Thanks for encouraging my technical english

@Cheez: In the originally equipped Felicia with A/C there is a single fan that works on two speeds. No two sperate fans. I checked the air flow. It works properly. But i though of adding an extra fan for the A/C but the A/C regassing technician told me it won't make a big difference as the problem (as he thinks) is a matter of weak Engine.

Ok, let's make some engineering conclusion (i am an electronics Integrated circuits designer so i claim myself to have a good engineering sense )

The car has two states: 1- running without A/C 2- running with A/C.

We have always two Coefficients: one for cooling and one for heating. In order for the car not to over heat it is assumed that the cooling coefficient should be higher (slightly) than the heating one.

Then, what is the source of cooling in the car ? The fan and the radiator water flow and the heating coefficient is the engine heat.

In the case of NO A/C, the cooling coefficient is higher when the fan is turned on (due to thermostat) and this leads to that the water becomes cool and the fan to turn off and in turns the coeffiecent of heating becomes larger and so on. This makes the car works pretty fine.

Let's go to the bad case :( when the A/C is turned on).

Now we have the cooling coeffiecient is at its max (fan is working at high speed, radiator almost new (changed couple of months ago), water pump totally new) and the car is still overheating. This directly means that the heating coefficient is higher than the cooling and they won't ever meet (i.e. they are diverging ).

So we have two options: Whether to decrease the heating coefficient (which i don't know how and i don't know the reason of being high from the beginning) and this can be done by adjusting the car engine) or by increasing the cooling coeffiecient of the car and this can be done by either replacing the tape water by green water or by adding another fan in front of the A/C cerepentine or both.

By the way, i had an A/C regassing one month ago. Although the A/C efficiency i really nice but i have a question, can a faulty regassing lead to overloading the engine for example and if so how can it be proved ?

Also, the A/C cerepentine is relatively in bad way. changing it can lead to a difference ?

Sorry for this long replay as also i am working as a teachning assistant in a university so i am fond of explanation

I hope that we can reach a solution.

Kindest Regards,

Mostafa

Mostafa

The header tank will always be hot when the engine is up to normal operating temperature, as coolant is fed back to header tank from the cyl head... thats normal.

A better way to determin if the engine is actually overheating is is to feel the top and bottom radiator coolant hoses.

If the bottom hose is very hot ie; much the same as the top hose, then yes your engine may well be overheating.

If both top and bottom hoses are cold then that indicates a ciculation problem, maybe an air lock, faulty thermostate or pump problem.

If however you find the top hose is hot and the bottom hose is much cooler then your engine is not overheating (provided your radiator is not blocked).

From reading your first post, I think you may have a wiring problem giving a wrong temperature reading. Your car may still have some undiscovered damage to the wiring loom or a crossed wire during the rewire.

I have tested the car today again. It worked pretty fine for like 45 mins while i am moving on average speed <5 Km/Hr :( Egypt traffic in rush hour is unbearable. When i went to the ring road and speeded up to 90 Km/Hr (max speed limit) the car started to slightly overheat. I have a strong guess but i need a technical confirmation.

I think that the A/C compressor is getting old so it moving harder so it loads on the engine more than it is expected. The problem in that guess is that the guy who made my A/C regass told me that the compressor is working pretty fine (but he might mis-diagnosed the problem).

I believe that this might be a problem. But can anyone tell me what is the method of validation of this problem ?

I'd certainly change the tap water for a dedicated coolant, and I'd suggest using G12/G12+ if you can get it there as that's the current VAG standard.

Egypt is, I'm assuming, pretty hot so it might just be that the tap water has deposited gun in the cooling system and that this needs flushing to remove it and filling with the correct coolant. This will provide a significant increase in the amount of cooling provided.

The AC compressor might well be an issue, but using a flush and filling proper coolant is a much cheaper option than replacing the compressor, drier and another regas.

When you put the a/c on you increase the load on the engine, which might cause it to overheat if the coloing is already marginal. This is a problem with the cooling system rather than the engine itself.

As others say, I would drain the cooling system, flush the engine and reverse flush the radiator (water runs in the bottom and out the top), then refill with G12+. I've already discussed my reasons for using anti-freeze even in a desert climate.

Edited 25 June, 200917 yr by KenONeill

FWIW you use G12 neat rather than mixing it as it comes pre diluted.

hi mostafa i know this problem this happens when you have a weak head gasket you said that when you go over 130 km heat starts to raise a bit if you wanna be sure check the hosess pressure by pressing it it will all have a great amount of internal pressure so check the head gasket next check the air condition external eveaporator fins may be closed from the pressure of the cleaning wate gun at the gas station cleaning section cause it's wrong to clean this area with High pressure water gun causes fins damage so no air can reach the radiator because it's behind the AC evaporator change the external evaporator