Running warm (non-mopar)

[Arthu®]

As you guys are the only automotive forum that I'm on and I have been indecisive on this I was wondering what your opinion on the matter is. The car is a 1975 Audi 80 LS, 1.5 automatic. Ever since I bought it, the temperature gauge has been almost in the red. I threw out the thermostat right after I bought it, thinking that was the problem as it had been sitting for a while, the problem remained that it was running almost in the red zone on the gauge. Since it is getting colder, it didn't warm up anymore during short drives. So I bought a new thermostat and installed it.

After making sure all the air was out, I took it around the block and it found out it was overheating (boiling even). So I took out the thermostat again and it turned out that the bypass was blocked with sticky almost sugar like goo. I got that all out and now the thermostat does open, the fan starts, but it still is near the red.

My thoughts are that there are probably more holes in the block blocked with goo and that that makes the temperature in the head go up due to a lack of circulation. So the way I see it, I have three options, one is a chemical additive that cleans the cooling system, but I am hesitant because it is an old car and it could cause leaks. Or I take it apart and try to find the blockage, but this would mean costs of a new headgasket and assorted small items. The last option is to just live with it and let it run pretty warm.

Oh by the way the temperature of the upper radiator hose when the engine is warm is around the 95 degrees Celsius (approx. 200 degrees Fahrenheit) the lower hose is around 80 degrees Celsius (approx. 175 degrees Fahrenheit) and the heater works perfectly.

What would you guys do? Thanks in advance.

Arthur

[femtnmax]

The sticky goo is not a good sign.  Buy an accurate thermometer; I have the type sold by SnapOn Tools.   They are accurate, especially the mercury filled ones.  Now you will know the true water temperature.
To check the electrical end of the sytem, on US built cars ground the wire to the temperature sensor located on the engine, and the temp gauge at the dashboard will show maximum temp(HOT).  Removing the ground the temp gauge will drop back to stone cold.  These electrical tests will tell you if the gauge is working ok.

But again, back to the goo...I would assume if the thermostat bypass hose as the goo in it, then the rest of the system has it to.  Did you buy the car recently??  Goo is something put in the cooling sytem to stop head gasket leaks, etc.  A couple ways to look at it:  1) Removing the goo could mean opening up other problems (there could be a bad head gasket, cracked head or block)  or 2) maybe only the radiator was leaking.  In that case take the radiator out and have it cleaned, or flush it out real good by yourself with something that cuts the goo.  I have used restaurant grade industrial strength kitchen degreaser to flush out gas tanks, etc with excellent results, so maybe try something like that.  For a badly gunked up gas tank, I fill the tank with straight solution or 50/50 mix with water, then let it sit at least 7-10 days, stirring once a day.  Flush with water.  The degreaser I use is biodegradeable with water.

Old time farmers taught me to stop a cooling sytem leak of almost any size, bring the engine up to temerature and pour in a full can of Bordens brand condensed milk (has sugar in it).  This will absolutely stop a water leak, don't even need hose clamps.   But imagine what the inside of the cooling system looks like.

[Cooter]

What would I do? Sell it. Sounds like Blown head gasket.

[Arthu®]

Thanks for the replies,

The temperature was measured with a thermometer from a shop, so this should be accurate. The gauge is working ok, I have tested that. I have bought the car this July and have since traveled about 10,000km with it. The entire time, the gauge never went in the red, not even when if it was 35 degrees Celsius in the sun and in traffic. If it were a cracked head/blown head gasket I would assume that it would either use water or oil and during that time, I only had to fill up the oil once with about half a liter. Both the oil and the coolant also seem relatively clean. I do know that the radiator is not original and was replaced because the old one was rusted too badly. Maybe they first tried to repair it with this goo. I think I will give myself a Christmas present and buy a new head gasket and just open it up to see what the problems are. I could of course just sell it as is, but it's a hobby car and I don't mind spending a few hours wrenching (it is a nice break from studying).

Again thanks for the advice, especially on the degreaser, I will try if that breaks down the goo.

Arthur