Ask Bob: Why Is It Overheating?

by Bob DeP.

Dear Bob:
I own a 1995 Dodge Neon with about 72,000 miles on it. This past fall (Oct. 98) my engine overheated half way through a two hour interstate trip. A couple of months before the overheat, I had noticed a bubbling, gurgling sound coming from the coolant reservoir, but was told that it was a "normal" thing for a car to do in the summer months. A few days prior to the engine overheat, I noticed a fair amount of coolant leakage - a running stream coming from behind the front passenger wheel, so I put more coolant in. The garage that looked at my car after it overheated said that there was practically no coolant in the engine.

They did a pressure test and told me that it was probably the thermostat. I had a local dealer install a thermostat but they didn't test drive it or do any diagnosis. The gurgling sound continued, but I noticed that when I turned the AC on, the the engine fan would come on, and it would pull the level of coolant in the reservoir down, and the bubbling/gurgling would stop. I took it to another shop, thinking it might be the fan sensor switch, and they said that I had a bad radiator cap and there was no pressure in the system. They put a new radiator cap on it, I picked up my car and started driving home and within five miles from the shop, the temperature warning bell came on and the engine temperature read High. HELP! Do you have any idea what the problem could be?

Dear Kim,
No one ever addressed where this "steady stream of coolant" was coming from. Behind the passenger wheel? Okay, but still, there should not be any coolant leaking at all!!! To me, that might be in a location where the heater hoses are. The system is probably not holding pressure because you have a bad hose. The gurgling sound is the coolant boiling in the radiator. You may have a bad fan not allowing the coolant to cool. If you keep driving like this, you WILL damage the engine.

Do this first, find out where that leak is coming from. Address that. Then do a pressure test This will tell you if there are any other leaks.

First make sure that the system holds pressure. Make sure that there is coolant in the system. With the cap off, run the engine, watch to see if the coolant is circulating in the radiator. While waiting for the engine to warm up, check to make sure that there is no debris in front of the radiator.

Now, when the engine warms up, the thermostat should open (about 10 or so minutes) when this happens, you should see the level in the radiator drop. If it doesn't, then it's possibly a bad thermostat. After a while when the coolant gets hot, the fan should come on. If not, then it's either a bad fan, switch, wiring, relay.
Good Luck!
Drive Safely!
Bob, The Auto Answer Man

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