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Thermostats, Auto, Car Truck

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Thermostat replacement: $50-$100 parts and labor
(Prices good for most domestic or import cars and light trucks)
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Purpose of a thermostat

Your engine is designed to operate at a certain temperature. Your engine does not run its best until it's "warmed up."

The purpose of the thermostat is to keep the engine temperature the same no matter what the outside temperature. The thermostat also helps the engine warm up more quicky.

On a water cooled engine, the thermostat blocks off the water (coolant) flow to the radiator until normal operating temperature is reached (usually 165 to 195 degrees). The "degrees" that a thermostat is rated is printed on the box and usually engraved on the thermostat itself. Most newer cars run at 195 degrees: they get better gas mileage that way. As the motor warms up, a paraffin pellet in the thermostat expands against a piston in the thermostat, pushing it open and allowing water to flow through the radiator. On a very cold day, the radiator may cool the water jacket of the engine too much. The thermostat will then close a bit, reducing the flow of coolant through the radiator and thus maintaining a steady operating temperature. .

Symptoms of a bad thermostat

A motor with a bad thermostat will run fine for the first few minutes, then overheat rapidly. Other symptoms include the engine and radiator making a rumbling, gurgling, boiling sound: like a steam pipe knock, if you've ever heard one of those. A thermostat sticking open can make your heater not work in the winter. A partially closed thermostat can make the car run a bit hot but not overheat.

Overheating can destroy a thermostat

When you overheat an engine from a coolant leak or whatever you can destroy the thermostat. It might not fail immediately, but the seal on the paraffin pellet that opens the thermostat can be compromised, and the thermostat often fails shortly thereafter. A thermostat will also fail from corrosion, and wear from many many cycles.

Doing without a thermostat

If you are broken down with a bad thermostat you can remove it and not replace it right away. You can put the thermostat housing back on and leave the thermostat out and the engine will still run fairly well. The problem is that the engine is designed to operate at a certain temperature, and especially in cold weather an engine without a thermostat will never reach optimum operating temperature. On a computer controlled engine (like, most all engines since 1980) the computer might not control the engine properly if it never fully warms up. (Bad gas mileage!) Below are pictures of a thermostat replacement in a Jeep Cherokee 4.0 Liter Motor.

A new thermostat usually comes on a card. The operating temperature is written on the card, usually 165, 180, or 195 degrees fahrenheit.

The 4.0 litre Jeep Cherokee thermostat location is typical: it is on the top front of the cylinder head. This nview is with the thermostat removed.

The thermosrtat sits in a groove machined into the head. Notice that I have drilled a hole in the thermostat flange: this small hole will allow any air, steam, or gas to bleed past the thermostat.

This is the thermostat housing

I like to glue the gasket to the part that gets removed from the engine. The bolts inserted backwards insure the bolt holes are aligned while the glue sets. I use 3m Super Weatherstrip Adhesive (yellow).

just before installation I like to put a light film of RTV silicone gasket maker on the other side of the gasket.  This will make up for any scratches or imperfections in the head side of the gasket. If you install paper gaskets this way you'll never have a leak!

Here it is back together with the engine running!  The temp sensor is at the top: that's the computer temp sensor. (2 wires)


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Thank you for visiting the ECONOMECHANIX WEB SITE. Please feel free to comment. We also serve the surrounding communities of Alachua, High Springs, Hawthorne, and Newberry! Gainesville has been my home since 1974, and I've loved Gvl and the Gators since I came here in the fall of 1974 to attend the University of Florida. I loved it so much I stayed and opened my car repair business. Originally it was out of the back of a 1963 Chevrolet wagon, but in 1977 a fellow mechanic and I opened an auto repair shop with actual walls, etc. I stayed in the same location for 26 years, and recently moved my operation to property I bought 15 miles east of Gainesville. I am doing most all the repairs myself now, having reduced my overhead from $1500 per month to practically nothing. I do work by appointment only. I mostly work only on my established customers cars, but I will occasionally take on new clients. E-mail me and I will either make arrangements to look at your car, or I will recommend you to someone who will.

George G. Scott, Jr.


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Auto, Car, and Truck Article List

A
ABS: Anti-Lock Brake Systems
ADVANCE: Car ignition timing
ALTERNATORS and Car Battery
AUTOMATIC TRANSMISSIONS
B
BAD CAR DESIGNS
BATTERIES: Auto, Car or Truck
BELTS AND HOSES
BEARINGS
BODY AND BUMPER REPAIRS
BRAKE REPAIRS: Car or Truck
C
Car Washing and Care
CARBURETORS:Car & Truck
CHECK ENGINE LIGHT
CLEANING: Engine Cleaning
CLUTCH REPAIRS: Car & Truck
COMPRESSION: Car Engine
COMPUTER CAR CONTROLS
CV JOINT OR CV AXLES
D
DISTRIBUTORS (IGNITION)
E
ELECTRIC WIRING REPAIR
ENGINES: Car & Truck
ENGINE CLEANING
EXPANSION PLUGS
F
FREEZE PLUGS
FUEL AIR MIXTURE
FUEL INJECTION: Car & Truck
FUEL PUMPS: Car & Truck
G
GAGES AND "IDIOT LIGHTS"
GASKETS AND SEALS
GLASS: WINDOWS AND WINDSHIELDS
H
HEADS & HEAD GASKET
HOSES AND BELTS
I
"IDIOT LIGHTS" AND GAGES
IGNITION TIMING: Car & Truck
J
AUTO JACKS: lifting cars safely
K
L
LEAN "Car runs lean"
LIGHTS: WARNING OR "IDIOT LIGHTS"
Limp Home Mode
M
MIL Light
MANUAL TRANSMISSIONS
N
NO START: Car Won't Start
O
OIL CHANGES
OIL: What's right for your car?
OIL LIGHT ON OR GAGE LOW
P
PCV Valve
Q
R
RADIATORS: Car and Truck
RICH: Car runs rich
S
SEALS AND GASKETS
SERVICE ENGINE SOON LIGHT
SPARK PLUGS
STARTERS: Auto, Truck
T
THERMOSTATS
TIMING: IGNITION TIMING
TIMING BELT & TIMING CHAIN
TIRE REPAIR
TRANSMISSIONS: AUTOMATIC
TRANSMISSIONS: MANUAL
U
V
VACUUM ADVANCE
WARNING LIGHTS OR "IDIOT LIGHTS"
Car Washing and Care
W
WATER PUMP REPAIR
WINDOWS AND WINDSHIELDS
WIRING REPAIR
X
Y
Z

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