Help...overheating!!!!!
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New User
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Help...overheating!!!!!
89 f150 5.0 5 speed..... here's the scoop...changed the t-stat,coolant, and flushed the heater core...when I just sit and let the truck run, rev it up occasionally with the heater on...then it runs moderately cool and I have heat in the cabin...I take it for a drive and after six to seven minutes it loses cabin heat and then the engine over heats...here is the kicker though...I can pull the radiator cap off and there is no pressure in it and i can top off the radiator with about a pint of water....heater hoses feel warm but the upper radiator hose is mushy and you can kind of hear air in it when you squeeze it...is it possible that the top hose is collapsing or do i need another radiator cap...what do i do....thx guys....undefined
Fleet Mechanic
Joined: Nov 2003
Posts: 1,372
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From: West Cornwall, CT
Did the truck have an overheating problem before the flush and thermosat change? If it was OK before, the problem was introduced when the work was done.
From your description of the problem it sounds as if there is a small leak that is causing coolant loss. There are a couple of easy things to check.
- Look at the thermosat housing to see if there is a leak. It is easy to create a leak when changing that thermosat.
- Check the weep hole in the water pump shaft. Tere is one hole on the top and another on the bottom. Coolant can leak out the bottom and you will not see it.
- As you mentioned, change the radiator cap.
You should get indications of high system pressure before the engine starts to overheat. There should be *lots* of steam and hot coolant spray if you remove the radiator cap from an overheated engine!
Lou Braun
From your description of the problem it sounds as if there is a small leak that is causing coolant loss. There are a couple of easy things to check.
- Look at the thermosat housing to see if there is a leak. It is easy to create a leak when changing that thermosat.
- Check the weep hole in the water pump shaft. Tere is one hole on the top and another on the bottom. Coolant can leak out the bottom and you will not see it.
- As you mentioned, change the radiator cap.
You should get indications of high system pressure before the engine starts to overheat. There should be *lots* of steam and hot coolant spray if you remove the radiator cap from an overheated engine!
Lou Braun
Elder User
Joined: Oct 2004
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From: Winnipeg, Manitoba
The hoses can contribute to this situation. I'd personally take it in and get it pressure tested, or borrow or buy a pressure tester and do it yourself. Curious, did you perhaps revers the hoses on the heater core when you installed the new one? This could create all sorts of havoc, and heat loss would be explained. As for no pressure....that's a leak of some kind, somewhere. You're going to have to check ever hose clamp and fitting to make sure it's not the culprit.
New User
Joined: Dec 2004
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how many times have you overheated? what does the coolant look like? if there is any signs of oil, you're done. pressure test the cooling system. there are 2 types of coolant leaks, cold and hot. start with a cold coolant pressure test, retest after engine has reached operating temperature. 90% of coolant leaks show up when the engine is cold. sounds like a coolant leak. i'm a tech, check for leaks first. if you found one, it doesn't eliminate another. repair the weakest link and retest. check the radiator for cold spots.
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From: houston
Take things one at a time. Lack of cabin heat could be low coolant. This could also be the cause of overheating. Lack of pressure in radiator could be from low coolant which means there is a lot of air in the system. The upper hose can't collapse because it is the exit hose from the engine to the radiator. The lower hose can collapse because it is under suction from the waterpump. But only if someone has removed the coil re-enforcement from inside it. It looks like a spring and prevents collapse at high RPM. Check to be sure the Stat is facing the right way. Also be sure there is a small hole in the flange of the Stat. This allows air to bleed through when the Stat is closed, this helps when filling. If there isn't one, just drill a 1/8" hole. It all sounds like the system isn't full. Good luck.
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overheating....
thanks guys for all the suggestions....didn't know about a hole needing to be in the t-stat...will need to check that...there is also no oil present so that is good news...everybody has said one common thing and that is that is has an airpocket or low coolant...gives me some things to work on this weekend...let you guys know how it turns out....thx,todd
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My '94 F-150 4x4 was doing about the same thing. We changed the heat sensing switch and then found out that we had a hose that was leaking and the hoses that were leading to my heater core were partially blocked. My truck (for the time being) runs at her normal temp and the heater is working...you might check those while you are at it.
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Shortly after I bought 'Ruby' my darling father wanted to make sure that my radiator didnt have a leak....he did this by adding "stop-Leak" to my radiator...DO NOT DO THIS!! I found that out the hard way...the stop-leak didnt flow all the way through and blocked my hoses. They had cleaned out and my mechanic saved me over $400. by flushing them out and getting that crud out of them
