you might have a blown head gasket and the coolant is leaking into the cylender and the engine is burning it.
Most of the time it is because the water pump is going out and it is leaking where the pulley is on the engine.
if you have antifreeze in the oil means you have a leaky head gasket.... or if your engine has the oil lines going to the rad like some s10s had get a pressure check on the rad could be leaking there as well
it could mean you need a new carburetor
It could be leaking from the water pump. There is a small hole in the bottom of water pumps that will leak coolant when the bearing id going out. This is so you have an indication of failure before it comes apart and destroys other engine parts.
could be your thermostat or you have no antifreeze coolant or your water pump is going bad
If losing anti freeze but not visible leaking typically means bad head gasket. Antifreeze is leaking into combustion cylinder and therefore evaporating and going out exhaust pipe as steam.
( Yes ) you might have an internal leak to the engine Is the engine oil level going up , or look " milky " With the engine warmed up and running is there white smoke coming from the exhaust pipe
Check to see if it is mixing with engine oil Run engine to normal operating temperature and remove oil dipstick, let a drop fall on hot part of engine - oil will smoke coolant will "sizzle" If so could be a sign of a bad head gasket It's not going anywhere in a Type 1 Beetle because we never used antifreeze in aircooled engines. In a New Beetle, it could be going one of three places. In ascending order of dread: You could have a leak you don't know about. Do you smell antifreeze inside the car? Heater cores do spring leaks occasionally. (Changing one is an awful job. Hope it's not that.) Heater hoses leak. Little pinholes you can't even see will cause leaks you can't find. You could have a bad head gasket. Or you could have a cracked block.
Are you referring to a loud exhaust sound? If so, it could be (Going from the engine back to the tailpipe) a cracked or leaking exhaust manifold - a leaking exhaust pipe - a leaking catalytic converter - a leaking muffler. That covers the exhaust system. If you are talking about a noisy clattering sound in the engine, you could possibly need a valve adjustment.
If it is smoking white smoke, it is getting in the engine and the engine is burning it. If not, it is leaking somewhere. Sometimes you hve to check it when it is cold as it seals off when it gets hot. GoodluckJoe
I'm not a mechanic / technician but it sounds like your heater core is leaking Have you noticed if your engine coolant level is going down ?
The reason the temp. gauge is going up and down is because it is low on coolant. Now where it is leaking I don't know, but you can start by checking these few things. First check the engine oil and see if it's over full or if the oil is white in color, If it is then the intake manifold gaskets are leaking coolant into the oil. You will have to replace the intake gaskets and change the oil and filter a few times within 5 to 10 mins. of engine running time to clean engine up. If the oil is okay when you check it and it's not white in color then it's not leaking into the engine and that's a good thing. Then Fill radiator up, put cap on and start engine. Take your fingers and fill around all 4 corners of the intake manifold where it bolts to the heads, or look at the corners real close to see if there is antifreeze leaking or a white resedu on the intake corners. If there is then the intake is leaking and you will still have to replace gaskets on intake. THIS IS A REAL COMMON PROBLEM WITH YOUR ENGINE.