My 2002 XLT with 5.4 has a bad thermostat (not closing so engine never gets to temp). My dealer wants $200 to replace the $17.00 part. Will I do any damage to engine (head gaskets etc) if i wait until the weekend to replace it myself (40 miles per day).

btw, unless it warms up it's worth the $200 to have the dealer do it since it won't fit in the warm garage.

 

as long as the thermostat is not stuck in the closed position where your engine overheats it should not hurt your engine

 

it shouldn't. since the thermostat is there it will provide some type of restriction, which will slow the flow of coolant and allow it get the heat out of the motor. in racing the run a plate with a hole in it. but you may not get hot heat in the cab.

 

For that price I'd be doing it myself or shopping around.
It's a very easy job on the 5.4L.

 

i just replaced mine two weekends ago on my 5.4. only hard part was getting the bolts loose on the thermostat housing. Those suckers were on there good. Overall it's an easy thing to do. Just take off 5.4L plastic shield, take off the intake tube, take off the bracket holding a resevoir (it has other bolts that keep it in place fine), then get those bolts loose. You will lose roughly a quarter to half gallon of coolant if i remember right so be sure to pick up a gallon of it. The thermostat should come out pretty easy. Just take the old one out, new one in with a new gasket (it's a large oring), and reassemble. I did have a very small seep from the thermo housing after i put it back together and started it up. I just made sure i got those bolts tightened down as good as i could and i assume that, with the heat cycle, helped seal it again. I got my stuff from o'reilly's came out to just over 10 bucks total. It isn't worth paying the stealership to do.

Since your in a cold climate, just get all the goodies and wait for a warmer day to do it. I ran with an open thermostat for over a year without really knowing. Then i got a CEL one cold night. Until you have a chance to change the thermo, just make sure you take it easy until the engine is warmed up. Good luck with it.

 

Running with an always open thermo basically just allows the sludge and what-not in the motor to build up because it never gets up to temp to dissolve it. If this is a couple week thing before you can fix it, then no worries, but yes, you need to let the motor get up to temp.

 

Really?, damn then i guess i'm running some seafoam through the crankcase before my next oil change (was plannin on doing it anyways).

 

Running it with the thermostat open will only cause the build up in your enginee nothing too serious to worry about, you will notice a lower mpg average but nothing to worry you, bright side you will have a better pick up form the standing still point.

 

it should not hurt it at all. there should not be a buildup of any sludge.

oh and changing the thermostat should only take you about 15 to 20 minutes. it is really easy to get to

 

so far so good. But there are two bolts and one plug (allen type) on each side of the block just above the oil pan. Which one is the coolant drain. I assume it is the plug with the allen type insert.

Better safe than sorry, so I'm asking the experts.

 

For anyone else trying this on, it's the allen plug. Could only see one on the driver side. Without a lift you have to be a real contortionist to get the lower hose off.