Occasionally overheating

[ezveedub]

Could be a bad radiator if the waterpump, thermostat and radiator cap hold pressure. My 95 A6 would overheat and the AC would shut off on the highway, but then cool down when city driving or short distance driving. Replaced the radiator and the issue went away.

[upallnight]

spewing from the expansion bottle means the engine is building up too much pressure in the cooling system. Your car is overheating which is causing the water to boil and turn to steam. You either have a bad thermostat, bad water pump or a clogged radiator. If the radiator is cold you have a bad thermostat, if the radiator is hot in one section but cool or cold in another section you have a clogged radiator. If the radiator is warm or hot throughout you have a bad water pump.

[sugaryling]

Originally Posted by ezveedub

Could be a bad radiator if the waterpump, thermostat and radiator cap hold pressure. My 95 A6 would overheat and the AC would shut off on the highway, but then cool down when city driving or short distance driving. Replaced the radiator and the issue went away.

I did flush the radiator form the top and water runs out the bottom hose just fine. Sure doesn't seem clogged.

[ezveedub]

Originally Posted by sugaryling

I did flush the radiator form the top and water runs out the bottom hose just fine. Sure doesn't seem clogged.

That won't tell you anything, that's why I said, you have to know all the components are fine. You usually have to feel or check the radiator with a temp gun when its overheating to know if it's cooling properly. Several cores can be blocked and the water will run through it fine with a hose, but it's running through the unclogged sections of the radiator core, not the entire radiator.

[sugaryling]

Gotcha! Well I don't have one of those temp guns. Maybe I'l get one from Harbor freight this weekend.

The cam alignment tool just arrived. I'm going to replace the thermostat in the next few days.

I've been driving for the past 4 days and the car hast over heat yet. This kind of makes me think that it's not the radiator or else it would over heat more often. What do you think?

[ezveedub]

Originally Posted by sugaryling

Gotcha! Well I don't have one of those temp guns. Maybe I'l get one from Harbor freight this weekend.

The cam alignment tool just arrived. I'm going to replace the thermostat in the next few days.

I've been driving for the past 4 days and the car hast over heat yet. This kind of makes me think that it's not the radiator or else it would over heat more often. What do you think?

Mine only overheated when ran on the highway with the AC on. Anything else, it seemed fine. If your car just overheats at anytime, check the other cooling system parts first. I would pressure test the cap to make sure its fine. I also use distilled water when mixing coolant also. Tap water has minerals and usually builds up deposits in the radiator core over time.

[Rob 635]

If you cannot find any other leak, go with a cap first (I think dealer is 30 bucks).In the meantime, if you are in tough driving conditions, put the heat on high. Try to see which happens first, temp gauge or steam from the engine.

[upallnight]

Unless you are replacing the timing belt, you could have replaced the thermostat without having to buy the cam alignment tool. It's a little bit harder with the timing belt still in place, but doable. You will also need the crank pin if you going to use the cam tool.

[sugaryling]

Camshaft alignment tool arrived and guess what? It doesnt fit! It's the correct width apart (unlike my 2.7T, it's wider) from cam to cam but the damn pins that goes into the cams are opposite. The small pin is lined up with the large hole and vice versa.

[sugaryling]

Originally Posted by Rob 635

If you cannot find any other leak, go with a cap first (I think dealer is 30 bucks).In the meantime, if you are in tough driving conditions, put the heat on high. Try to see which happens first, temp gauge or steam from the engine.

I can't find any leaks. No puddles or drips on the floor.

I replaced the cap today. Less than $2 for a Meyle one. Now when the temp gauge overheats, I pop the hood to check and steam and is hissing from under the coolant tank and rising up and around it. I think I'm going to replace the coolant tank next and see what happens. Before I replaced the cap, when I pop the hood, I would find coolant spewing from the side of the cap. New cap, no more spewing.

I'll try my best to monitor the temp gauge vs. steam from the hood.