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Jerry, Master Mechanic
Category: Lincoln
Satisfied Customers: 17219
Experience:  ASE Master certified, 30 years experience. Auto troubleshooting, electrical , ABS, SRS, EFI system
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Engine was overheating. Replaced thermostat but it gets

Customer Question

Engine was overheating. Replaced thermostat but it gets super hot on the top radiator hoses but not on the bottom ones. Blows cold air on full defrost. Runs about 5 minutes and then coolant overflows the reservoir. 2004 lincoln aviator. 4.6 dohc v8.
Submitted: 2 years ago.
Category: Lincoln
Expert:  Jerry replied 2 years ago.
Hello and welcome. My name is ***** ***** I will be happy to assist you today.
They are sometimes bad about the radiators clogging up and causing an overheating. You can have that tested at a radiator shop or feel around the core when the engine is hot to see if there are any cool spots that would indicate a clog.
However, with any engine that runs hot, overheats or has been overheated it is best to check the integrity of the engine, (head gaskets and heads, etc.)
The first thing that you want to do is check the cooling system for any exhaust gases. Make sure that it’s full first. There is a tester for that, that you can get from Autozone for about $20. They will normally lend you the tester and you just buy the fluid for about $8. It comes with instructions, but there is a blue fluid that is used in it, if the fluid turns yellow, that is exhaust gases.
Block tester available is:
Napa BK.(###) ###-####
Part Number:
*****You will want to check it at different RPM’s and at different temperatures***
If there are any exhaust gases in the cooling system, that will cause more pressure than desired and will allow the engine to burn coolant and/or heat the coolant up too high. Most times not filling the crankcase with coolant either and not smoke out the exhaust.
If there are, then there would be an internal engine problem, like a head gasket or head.
Please don’t forget to rate the answer, **** THAT IS THE ONLY WAY I GET PAID **** if you need any more on it, I will be here.
Customer: replied 2 years ago.
I can't tell about the temperature in the radiator as its all shrouded off. But it seems odd that the top side hoses get too hot to handle and the lower hoses are cold. Could it be a blockage?
Expert:  Jerry replied 2 years ago.
It could be that the pressure is too high in the system for it to circulate. Normally, even if the radiator were clogged it would be equally warm top to bottom.
Customer: replied 2 years ago.
My gauge is reading erratically also. Where is the coolant sensor located?
Expert:  Jerry replied 2 years ago.
That could also be an after effect of high pressure in the cooling system, where the coolant can't circulate as it should. However, the coolant temp sensor is in the front of the engine. Here is a diagram of it's location.
Customer: replied 2 years ago.
I am currently trying to burp the system and am adding more coolant. I finally got the pressure relief to open - on the coolant bridge.
Expert:  Jerry replied 2 years ago.
Ok, thanks. I may have to log off early today, my sister is in from out of town, please have a great and safe Memorial Day weekend, thanks