PO128 Code 2003 Lincoln Town car

john8234

Newbie
Joined
Apr 1, 2008
Messages
6
Points
1
Make
Lincoln
Model
Town car
Year
2003
Miles
64000
Engine
4.6
Hi,
Got a P0128 code on a 2003 Lincoln Town Car, 64,000 miles 4.6 Liter.

Scanner says:
Coolant thermostat below thermostat regulating temperature
Non-mil 1/2
Confirmed 2/2

Reset computer and drive about 60 miles (mostly highway speeds) and it did not come back on.

No leaks, coolant level fine, heat works well, no gurgling heard in cooling system, temperature gauge within normal range.

I'm thinking the themorsat is on its way out?

Any damage if I keep driving it ( either with or without the service engine light on)?

Thank you
 

billr

wrench
Staff member
Joined
Mar 12, 2007
Messages
7,040
Points
63
It could be a bad t-stat, but also could be something in the temperature sensing system; the ECT sensor or wiring or even PCM. I don't know which way is easier on this vehicle to check the temp system; use an immersion thermometer in the coolant or remove ECT sensor and use live-data to see how it reads in both boiling and ice water. What is know to be easy, for a first check, is to use live-data to see if the ECT is same as ambient after the car has sat unused for many hours (overnight or more).

Damage? Not too likely, but if the ECT reading is low then the cooling fan may not come on if the engine gets hot enough to need it and the engine over-heat. That is inconvenient, at best, and could cause considerable engine damage at worst. Again, probably not likely in present winter season.
 
Last edited:

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
11,814
Points
63
Location
St-Hyacinthe, Quebec, Canada
Yeah I am going to second billr, this is usually a sticking t stat.

Also a good time to flush the system.

When I do client flush, I also add a lubricant additive. Helps the old pump, cuz they suck to do on these engines.

I would say, 9 times out of 10, a t stat fixes the issue, and here, you dont want to buy napa, buy oem. Hint.
 

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
11,814
Points
63
Location
St-Hyacinthe, Quebec, Canada
in a engine like this, half a bottle of this should do. Good for two flushes.

We use a valvoline kit, but this amsoil stuff is very good also. Its called preventive maintenance.

 

Mobile Dan

wrench
Joined
Mar 1, 2002
Messages
3,725
Points
48
Location
Kentucky
My opinion....do nothing, and see how long it takes to re-occur. Changing the t-stat is easy, but there is a good chance that the housing will leak at the bottom after the job is done. That means you need a new intake manifold, probably. $$$
 
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