Thermostat Questions

Mafia Mustang · Mar 4, 2010

Here is an update .. Removed the old T stat it was stuck open .. put new one in and now it gets hot faster and is actually bubbling out .. I'm thinking this one may be stuck closed it's a stant too grrrr any Ideas or u think I may have a bigger problem?

91StangGT5.0 · Mar 4, 2010

Mafia Mustang said:
Here is an update .. Removed the old T stat it was stuck open .. put new one in and now it gets hot faster and is actually bubbling out .. I'm thinking this one may be stuck closed it's a stant too grrrr any Ideas or u think I may have a bigger problem?

Did you test it in a pot on the stove before installing? I always do this to ensure that they open at specified temp and open and close properly. Sometimes you can buy bad ones as said in an earlier post. I bought a new stat today (Mr. Gasket Balanced 180*) and I tested it in a pot of hot water and it opened right at 180* and started closing at 179*. It's all about luck lol.

91StangGT5.0 · Mar 4, 2010

Well I drove a little farther today in low 70* weather all highway (around 15-18 miles) and the temp gauge went up to around 228*-230* and pretty much stayed there for about 6-8 miles of the drive.

Mafia Mustang · Mar 4, 2010

Ya I'm Doing that tomorrow for sure .. should I return the one I installed? This Just occured to me If My last Tstat was stuck open and I was still getting hot I must have another Problem as well ... GREAT lol opinions?

tannerc91gt · Mar 4, 2010

You can overheat with an open t-stat...

91StangGT5.0 · Mar 4, 2010

May take longer with tstat stuck open though, but eventually it will.

RatStang · Mar 5, 2010

91StangGT5.0 -

Did you try closing up that cowl ram? If not, just squeeze a big car wash sponge or something in there just for test purposes and then get up to cruise speed. I don't think that, that alone is going to solve all ur problems but you should stop gaining temp as you cruise.

RatStang · Mar 5, 2010

Mafia Mustang said:
Ya I'm Doing that tomorrow for sure .. should I return the one I installed? This Just occured to me If My last Tstat was stuck open and I was still getting hot I must have another Problem as well ... GREAT lol opinions?

Sir... just looking at what you've posted so far....

I would day that your radiator is hosed. It's either too small, or plugged with scale, or has a tiny leak in it somehwere (could even be above the liquid line), or some other portion of your cooling system has some small leak.

If your old t-stat was stuck open, then that is likely because your coolant was too hot. Look carefully at the old tstat. Is it LOCKED open? If it is, there would two small brass clips (one each side and on the same side as the spring assembly). If it is in-fact locked open, then that means that your cooling system got even hotter than ANY tstat can deal with using the OEM housing etc.

Remove the radiator cap... look down in there as best you can and see if there's any kind of visible build-up. If you can see a little from the top, then it's much much worse toward the middle of the radiator. In that case... the best bet would be to replace it. I've tried many kinds of engine flush and have not found one that was worth the price I paid for it. C.L.R. use to work but it's so diluted these days that it's just as innefective as every other product on the market.

Now is your chance to get that aluminum radiator you've always wanted but kept putting off. There are some GREAT deals on ebay to be had for aluminum radiators.

I'm actually working the bugs out of the inverse problem you guys are having. My radiator is overkill, it's still 20* up here (on a good day), and my temp goes down down down, at cruise speed. lol I bought one of those tstats with the large bypass holes in it... I think they're too large for up here in the frozen hell.

Mustang5L5 · Mar 5, 2010

91StangGT5.0 said:
Quite possibly the best way someone has analyzed my problem thus far.

It may be overanalyzing...but it's true. Open scoops can create positive pressure in the bay and cause cooling issues.

First thing i'd do is reinstall the lower air dam and then go from there.

91StangGT5.0 · Mar 5, 2010

Well I changed the thermostat in my car just a few minutes ago and found out that the one in my car was stuck open :X For how long it's been stuck open I don't know, but it seen 225* Thursday. I installed a Mr. Gasket 180* Tstat and burped it/bled the system and the gauge only goes up to right at 180* and stays there after multiple revs and mid range rpm holds for reassurance...next is to take it for a drive.

91StangGT5.0 · Mar 5, 2010

Drove the car and noticed that the engine warms up a lot better and quicker now and seems to stay near 180-190* when cruising on a major city road at about 50 mph. it will drop a bit when I sit at a stop light in the midts of the drive. I think the air dam may cure it but I also may think the transmission may be getting warm too and making the engine run hotter. I have a trans cooler but it's mounted barely inside of where the electric fan pulls air. It was there when I bought the car...just noticed it.

91StangGT5.0 · Mar 17, 2010

Update. I installed the black air deflector under the radiator support and it seems to be helping ALOT! The problem I have now if that my temp goes up to 185-190ish then the temp drops to 180*, then goes back up slowly, then drops again, but even slower. Sometimes it goes up and down for a couple times then eventually stops going back down and rises toward 200* especially if I'm in stop and go traffic. When I get going again and get air pushed through the radiator by going a good speed, the temp will slowly drop a couple degrees, but as soon as I slow down and cruise slower or stop at a light, it goes up again. I mean don't get me wrong it was 75ish* outside and my temp stayed at or below 200*, which is a BIG improvement nonetheless! Better than 230* in 15 minutes like last year in the fall when it was mid 70s! If there are anymore suggestions on how to keep it around 180* or consistant please let me know! I do have a Mark VIII 2 Speed Fan that's sitting in my garage with a thicker 3 core radiator if that would help. I've also looked into high flow water pumps (not sure if I have one already since it was new when I bought the car.

Tanus · Mar 17, 2010

temp fluctuating up and down is normal, its the thermostat opening and closing. If 200 is as hot as it gets your perfect. If you have a electric fan definatly throw it on, should run cooler and will free up some hp too.

phutch11 · Mar 18, 2010

One thing to remember with the stock thermostat is that most stock ECUs pull 2 degrees of timing at 190 degrees.

OP, thus I think you made the right call with the 180 thermostat, at least as far as power is concerned.

Good luck....

67coupe · Mar 18, 2010

91StangGT5.0 said:
Update. I installed the black air deflector under the radiator support and it seems to be helping ALOT! The problem I have now if that my temp goes up to 185-190ish then the temp drops to 180*, then goes back up slowly, then drops again, but even slower. Sometimes it goes up and down for a couple times then eventually stops going back down and rises toward 200* especially if I'm in stop and go traffic. When I get going again and get air pushed through the radiator by going a good speed, the temp will slowly drop a couple degrees, but as soon as I slow down and cruise slower or stop at a light, it goes up again. I mean don't get me wrong it was 75ish* outside and my temp stayed at or below 200*, which is a BIG improvement nonetheless! Better than 230* in 15 minutes like last year in the fall when it was mid 70s! If there are anymore suggestions on how to keep it around 180* or consistant please let me know! I do have a Mark VIII 2 Speed Fan that's sitting in my garage with a thicker 3 core radiator if that would help. I've also looked into high flow water pumps (not sure if I have one already since it was new when I bought the car.

Heating up at lower speeds is a clear indicator that your fan is not moving enough air. Previously, you mention that you are using a 15" fan. What type of fan exactly?

If you have an upgraded alt, I would use the Mark 8 ASAP. If still using the stock alt, you could wire the Mark 8 on low speed. I ran my car this way for a long time prior to upgrading to a 3g.

91StangGT5.0 · Mar 18, 2010

67coupe said:
Heating up at lower speeds is a clear indicator that your fan is not moving enough air. Previously, you mention that you are using a 15" fan. What type of fan exactly?

If you have an upgraded alt, I would use the Mark 8 ASAP. If still using the stock alt, you could wire the Mark 8 on low speed. I ran my car this way for a long time prior to upgrading to a 3g.

It's a Flex-a-lite electric fan. My alt is definately not stock it's a motorcrafts alt, but I do not know the amp rating. I have a 200A Alternator I'm about to install anyway....plus I'm putting the stock crank pulley back on too, so we'll see what happens after that. I also figured the fan wasn't pulling enough air through a somewhat used A/C condenser and a transmission cooler. As far as how hot it gets, I'm not sure with the addition of the air deflector, but I do know I can do all the highway driving and it will stay between 180* and 195*ish. If I get stopped by a light or traffic it will get to at least 200*, but by that time I'm back home from driving from work, so I never continued to drive to see. Mostly out of fear of pushing the thermostat too far and getting it stuck open or closed.

Mafia Mustang · Mar 27, 2010

*update* I installed the Housing With No Tstat For A Test. The Car Runs Cool For A while but once it starts getting hot it gets up there fast .. I have an Aftermarket 3 core radiator that barley fits in the brackets but the car did sit for about a year or two . The Uppper radiator hose is still pressurizing That why I Want to eliminate the radiator .. anyone else had a similar problem?

Mafia Mustang · Mar 28, 2010

stang0f87 · Apr 4, 2010

hate to hijack but i was wondering what tstat to try. gotta 87 gt. just gotta ford motorsports aluminum radiator. pretty much stock except for gt40 heads. i've heard its possible to run it too cold. i was thinkin a 180. what u guys think?

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