Not understanding whats goin on
Hall Of Fame
Joined: Mar 2009
Posts: 19,168
Likes: 23
From: South GA
The great thing about a coolant system is there are only a few parts to it.
Hoses
Radiator
Rad cap
T-stat
Water pump
Heater core
Your hoses either hold water or they dont. If you can run the engine and both the upper and lower hose are hot then you are circulating water. If only ONE hose is hot and the other is not then its time to check the T-stat and/or water pump. If you replace the T-stat or boil it in water and find it works then move onto the water pump. If you pull it and the seal and impeller are fine or if you replace it anyway and you STILL are overheating, then its time to pull the heads and have them checked at a machine shop and replace the head gaskets.
Hoses
Radiator
Rad cap
T-stat
Water pump
Heater core
Your hoses either hold water or they dont. If you can run the engine and both the upper and lower hose are hot then you are circulating water. If only ONE hose is hot and the other is not then its time to check the T-stat and/or water pump. If you replace the T-stat or boil it in water and find it works then move onto the water pump. If you pull it and the seal and impeller are fine or if you replace it anyway and you STILL are overheating, then its time to pull the heads and have them checked at a machine shop and replace the head gaskets.
Registered User
Joined: May 2010
Posts: 1
Likes: 0
Got an '03 4.7 with a similar problem. Here's what I've noticed:
- only overheats a highway speeds, never from driving slowly through the city at < 35mph
- overheats at highway speeds mostly when its above 50 degrees, and the warmer it gets the slow I have to go to maintain it cool. At above 80 degrees its about 53mph. At 60 degrees its about 60mph. Below 40 degrees no cooling issues.
- it overheats when I hit small hills, cooling when it goes down the hill.
- the overheating never goes beyond the 3/4 mark, mostly cause I slow down to keep it cooler. Normally sits a needle below the 1/2 mark.
- has gone through 5 or 6 heater cores (problem went away when I dropped the big $ and had the dealer do it).
- no smell of coolant (see above - I know the smell and there is zero).
- dealer said zero coolant in the exhaust and zero leaks (its been a year and the coolant level is still good). So they didn't think it was a leaking head gasket. They suggested maybe the thermostat and a new clutch fan ($400 total - told them I'm not spending $400 on their guess...)
- at slow speeds it stays cool.
Work I've had done:
- heater core, radiator, thermostat a year ago.
- y-pipe and catalytic converter a month ago.
- all work has been done by a dealer.
Anyone have any clues???
- only overheats a highway speeds, never from driving slowly through the city at < 35mph
- overheats at highway speeds mostly when its above 50 degrees, and the warmer it gets the slow I have to go to maintain it cool. At above 80 degrees its about 53mph. At 60 degrees its about 60mph. Below 40 degrees no cooling issues.
- it overheats when I hit small hills, cooling when it goes down the hill.
- the overheating never goes beyond the 3/4 mark, mostly cause I slow down to keep it cooler. Normally sits a needle below the 1/2 mark.
- has gone through 5 or 6 heater cores (problem went away when I dropped the big $ and had the dealer do it).
- no smell of coolant (see above - I know the smell and there is zero).
- dealer said zero coolant in the exhaust and zero leaks (its been a year and the coolant level is still good). So they didn't think it was a leaking head gasket. They suggested maybe the thermostat and a new clutch fan ($400 total - told them I'm not spending $400 on their guess...)
- at slow speeds it stays cool.
Work I've had done:
- heater core, radiator, thermostat a year ago.
- y-pipe and catalytic converter a month ago.
- all work has been done by a dealer.
Anyone have any clues???
Registered User
Joined: May 2010
Posts: 1
Likes: 0
From: Houston TX
Have either of you checked for bugs or anything clogging your radiator? It will cause overheating if air cannot get through the radiator. Also, on my 02 I had the electric fan go out and it gave me a similar problem. Also, before I replaced my fan I had the radiator go out and the only way I knew was someone was standing in front of my truck when I drove up and it was hot! I was actually pissing water out of a small hole that I couldn't see unless it was under a load. (HOT!!)