Engine Thermostat stuck open?

Cory Berg · Nov 26, 2012

So I'm pretty sure I have a thermostat stuck open, just wanted to throw it out there for some feed back. The temp gauge never really comes up to temp from cold, except when sitting in traffic. It does have a 3 core radiator (brand unknown). Also, I get mildly lukewarm heat from the heater that goes cold if I try to turn the fan up at all.

So two questions;
1) Can a motor running cold cause performance issues? i.e. misfire under acceleration
2) When I dig into it, what stat should I use? is 192 ok?

ratio411 · Nov 26, 2012

Your stat may be stuck open, or too low temp.
I'd use at least 180*.
A 160* or stuck thermostat is going to keep the ECM from seeing operating temp, and it will never get into operating tune.

Cory Berg · Nov 26, 2012

That's what I thought, thanks!

Bill Gordon · Nov 26, 2012

Also, low engine temps will not burn the condensed moisture out of the oil. You can see this when you drain the oil and it has a milky color to it. Run a 180...

mikestang63 · Nov 26, 2012

IMO run the stock FOMOCO stat. That is what the engineers designed the motor for and the engine runs more efficiently when the operating temps are higher. People often throw in a lower temp stat to bandaid fix or cover up other cooling systems problems.

Cory Berg · Nov 27, 2012

I think that kind of explains itself...

The old one was a 160*, ditched that for a 180* Murray.

Now I can have my windows defrosted on my way to school!

89stang1 · Nov 27, 2012

Cory Berg said:
I think that kind of explains itself...

The old one was a 160*, ditched that for a 180* Murray.

Now I can have my windows defrosted on my way to school!

if u didnt put it in yet drill a couple small 1/8 inch holes in flange. I had my therm freez shut it wouldnt open so it built pressure and popped my upper rad line off and dumped coolant all over my new 333 stroker that had only 750 miles on engine. Also put a little crack in my hood, only downside to drilling a couple holes is it will take a little longer to get heat but atleast some coolant goes into motor if therm wont open and it makes coolant flow better

Cory Berg · Nov 27, 2012

It's already in, there's one little hole to relieve pressure. But I don't see how it would build pressure on the upper radiator hose. All the pressure would be on the lower hose right?

ratio411 · Nov 28, 2012

Bill Gordon said:
Also, low engine temps will not burn the condensed moisture out of the oil. You can see this when you drain the oil and it has a milky color to it. Run a 180...

This is true if most of your trips are short and can happen to any stat if you don't drive it far.
It just takes the lower temp stat longer to do the job, so short commutes on a regular basis with a 160 stat is a no-no.
Drive it a bit more, and it's fine.

ratio411 · Nov 28, 2012

mikestang63 said:
IMO run the stock FOMOCO stat. That is what the engineers designed the motor for and the engine runs more efficiently when the operating temps are higher. People often throw in a lower temp stat to bandaid fix or cover up other cooling systems problems.

Since the EPA has been involved in car building, the stats have been higher temp than even the manufacturers would like, not for performance or reliability, but to make the engine hotter for less emissions. So what FoMoCo put in there might be higher than optimum due to emissions regulations.

ratio411 · Nov 28, 2012

Cory Berg said:
It's already in, there's one little hole to relieve pressure. But I don't see how it would build pressure on the upper radiator hose. All the pressure would be on the lower hose right?

The lower hose is suction. Never really sees any pressure in normal operation because the pump moves water continually, even if it's through bypass.

As a side note, if you have a lower hose without a spring inside, get one with a spring, or get ahold of a spring from a junk hose to install into yours. I have even made springs out of a coat hanger... The lower hose gets enough suction put on it that when it gets age on it, or in the event of a cooling system problem, that it can suck shut and stop all water going into the engine! It'll take out a head gasket(s) quick. Ask me how I know...

srtthis · Nov 28, 2012

89stang1 said:
if u didnt put it in yet drill a couple small 1/8 inch holes in flange. I had my therm freez shut it wouldnt open so it built pressure and popped my upper rad line off and dumped coolant all over my new 333 stroker that had only 750 miles on engine. Also put a little crack in my hood, only downside to drilling a couple holes is it will take a little longer to get heat but atleast some coolant goes into motor if therm wont open and it makes coolant flow better

isnt that what the bypass hose does?

Cory Berg · Nov 29, 2012

ratio411 I think I recall reading your thread about that... I'll make sure to check next time I'm under the hood.

Just curious here, but what kind of temps should I be seeing? It sit's at the A on the gauge, what is normal for a 5.0?

89stang1 · Dec 1, 2012

srtthis said:
isnt that what the bypass hose does?

huh? this is what i was saying if he didnt install therm yet to do this worked for me
http://forums.mustangandfords.com/7...-drivetrains/289-blown-head-gasket/page4.html

88LX5.Oh · Dec 2, 2012

Cory Berg said:
ratio411 I think I recall reading your thread about that... I'll make sure to check next time I'm under the hood.

Just curious here, but what kind of temps should I be seeing? It sit's at the A on the gauge, what is normal for a 5.0?

Our gauges are all over the place. If you want an accurate reading, get an aftermarket gauge.

ScreamnV8 · Dec 2, 2012

Hey
Not trying to hijack but i do have a similar issue.
car has been running cool for a while now, being constantly at 120 degrees even when driving for a while, it only climbs if i idle for about 20 minutes and it goes to 160 max.

I have changed the heater core, thermostat, aftermarket gauge and the radiator cap with temp readout. No leaks have been seen or anything of that sort, i do blow out kind of thick white smoke when cold until it warms up but i also have no cats .

It never overheats nor does it get even close and takes about 15 mintues to warm up the heater temp to. any idea's? And should i be expecting any bad effect from this?

7991LXnSHO · Dec 2, 2012

Cory Berg said:
ratio411 I think I recall reading your thread about that... I'll make sure to check next time I'm under the hood.

Just curious here, but what kind of temps should I be seeing? It sit's at the A on the gauge, what is normal for a 5.0?

"M" to "A" is about right for my car with the sender post cleaned and a new stock temp thermostat in. But it was all over the place and an aftermarket gauge is a great idea.

Cory Berg · Dec 2, 2012

If I could afford an aftermarket gauge, I would definitely go for one. Being a broke college student kinda sucks

ratio411 · Dec 3, 2012

ScreamnV8 said:
Hey
Not trying to hijack but i do have a similar issue.
car has been running cool for a while now, being constantly at 120 degrees even when driving for a while, it only climbs if i idle for about 20 minutes and it goes to 160 max.

I have changed the heater core, thermostat, aftermarket gauge and the radiator cap with temp readout. No leaks have been seen or anything of that sort, i do blow out kind of thick white smoke when cold until it warms up but i also have no cats .

It never overheats nor does it get even close and takes about 15 mintues to warm up the heater temp to. any idea's? And should i be expecting any bad effect from this?

I wonder if your gauge is wrong?
120* is VERY low, the car wouldn't be running properly as the ECM needs to see a minimum temp to run in tune, and the heat wouldn't be blowing any sort of air I would call warm/hot.
The problems you will run into if you are really running temps this low are:
Sludge buildup and contaminants building up in the engine, creating destructive acids.
Poor performance and economy from the ECM being in a closed warm up state constantly, instead of actively running a normal tune.

7991LXnSHO · Dec 3, 2012

You can get a 2" mechanical Temp gauge for about $20 with tax at Advanced Auto - do you like black or white faces? I have had one 20+ years old in another car I paid abuot this for back then, also Sunpro.
http://shop.advanceautoparts.com/we...unpro_9030006-p?searchTerm=temperature+gauges+
http://shop.advanceautoparts.com/we...npro_17122010-p?searchTerm=temperature+gauges+

I think the pods that fit the A pillar usually take 2 1/16", but it is not worse than party or a pizza study night. Why haven't I done this? I can not decide where to put the gauges- on the dash or on the pillar or near the radio. I'm certinly not blocking any AC outlet to do it. In a late 87 (?) Merc. Cougar, I made a template for below the radio with a piece of sheet metal, tin snips and a hole saw or careful cutting. With black paint it looked just right. I bet I will ask Santa for a pre made gauge holder and get it done too.

Engine Thermostat stuck open?

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