Hey guys need some help with a overheating issue that has happened only twice in 4 months. Both times it has occurred there has been some slow driving in traffic then a small uphill climb. The AC gets warm then the alarm goes off with the gauge showing a high temp.. I stopped the first time and noticed that the water level in the expansion tank was low so I added some to the proper level and it ran fine until it happened again yesterday. Both times there has been no water leaking from the truck or are there any obvious leaks around the engine. No water in the oil either. Im pretty good with the basics but this problem has me by the *****. Any suggestions or tests to try would be awesome. Thanks.

 

When this happens do you have reason to believe it is actually overheating? Meaning does it boil at all or are there other signs that it is actually getting that hot or is it possibly a sensor that is bad and triggering these responses? I have (AND use) an infra-red temp gun and that would tell you if the radiator is actually getting that hot or if it is bad sensors. The water level in the expansion tank shouldn't be a problem because if there is even water in there it is an indication that the system is full. How many miles on it? Is there a chance the fan clutch is getting weak? If it is actually getting that hot you should be able to tell that the fan clutch is fully kicked in by the noise it makes. You should also be able to feel the air produced by the fan by putting your hand in the area where the air comes out of the shroud. If it is actually that hot the fan should be putting out big time. BEWARE: keep your hands away from ANY MOVING PARTS if you try this test. You can't look at the fan and tell if it is fully kicked in but there is a huge difference in the air movement with low temp and high. Also, if the fan clutch is worn, you should tell by how easily it turns by hand when it is hot. OBVIOUSLY, turn ther truck off before trying this. If the fan clutch is working properly there should be some drag to it immediately after shut off.

 

Thx for the reply. The truck has 140,00". I haven't putmy temp gun on it only because I haven't had it with me but I think I'll put it in the truck in case it happens again. Thx for the tip on how to check the fan. I will test that one ASAP. As far as the water level it only has a hg inch in the bottom of the tank when this happens. I filled it up and it lasted 4 months and when it happened the other day the level was a half inch again. There no boiling over or any indication of a water leak. Should I have to add water to this tank every 4 months if so this is the first truck I've had to do this to. I'm gonna. He k the plugs and the coolant system for leaks this week. Any other thoughts are appreciated. I'll post the results of my tests. Thx again.

 

The answer is no, you shouldn't have to add water. Having said that, it would be very unusual to go say 2 years and the water level in the bottle never go down at all, but generally speaking if you're having to add because the overflow is almost empty, It IS going somewhere, even if not rapidly. My suggestion would be to do a pressure test on the system of about 20 lbs or so at least. I would do it when it's warmed up fully. Give it a little time with that prtessure on it and see if the pressure drops at all, and also check thoroughly to see if any leaks are visible. That amount could be lost by a faint head gasket leak and wouldn't show up on a pressure test or on a spark plug. If the leak is slow enough it can easily burn it off without showing.

 

Just an observation here is that you say in your posts that you are adding water...no mention of "coolant". If by chance you are just adding water then first off water is not as efficient at cooling as actual 50/50 mix is. Second if you have a bad degas bottle cap which regulates the system pressure you can be losing pressure and allowing the "water" to steam off or evaporate from higher coolant temps allowed by low system pressure. Just want to make sure everyone is on the same page as there is a big difference between a 50/50 mix, just water or a poor coolant to water ratio in the coolant system. take care.

 

Well thx for the help and suggestions. I found a small leak that was barely noticeable. I pressurized the system with the help of a buddy's tool. We found a ever so small hole at the bottom right side of the radiator. It was so small i guess that it took 4 months to slowly drain the tank. Anyway thx for the input and I hope to be able to give my 2 cents one day. Aloha