My new car gets 13 miles to the barrel, but the thermostat is broke

[Ericman197]

I think the thermostat is stuck open vv

It's a 1975 Plymouth Duster with a 340. Just about everything is new or rebuilt.

Symptoms:

A. If I drive the car around, the temp gauge goes just a tad above 120 F and never higher. Ever.

B. If I let the car idle for a long time it will eventually heat up to approximately 180 F on the gauge. However it started bogging a little so I drove it around and within a couple of miles the temperature dropped back down to 130 F.

The previous owner put in a 185 F thermostat right before he sold me the car, so I'm thinking maybe it is defective (stuck open). My fear when letting the car heat up by idling is that MAYBE the temperature gauge is off, and it's running hotter than I think. This is why I didn't let the car idle longer: what I heard as bogging might have been nothing, but at the time I thought "SHE'S GONNA BLOW!" The engine fan works.

So what say you, TB? I can post pics later if anyone is interested.

[hbarcat]

Originally Posted by Ericman197

I think the thermostat is stuck open vv

It's a 1975 Plymouth Duster with a 340. Just about everything is new or rebuilt.

Symptoms:

A. If I drive the car around, the temp gauge goes just a tad above 120 F and never higher. Ever.

B. If I let the car idle for a long time it will eventually heat up to approximately 180 F on the gauge. However it started bogging a little so I drove it around and within a couple of miles the temperature dropped back down to 130 F.

The previous owner put in a 185 F thermostat right before he sold me the car, so I'm thinking maybe it is defective (stuck open). My fear when letting the car heat up by idling is that MAYBE the temperature gauge is off, and it's running hotter than I think. This is why I didn't let the car idle longer: what I heard as bogging might have been nothing, but at the time I thought "SHE'S GONNA BLOW!" The engine fan works.

So what say you, TB? I can post pics later if anyone is interested.

I'll assume for the moment you've made sure that your entire cooling system is full of coolant and there are no large air pockets anywhere.

If so, then it's almost a certainty that your thermostat is stuck open. They're CHEAP and easy to replace on that engine. Buy a new one and replace it, making sure it's installed in the proper direction. On the slim chance that this doesn't fix your problem, buy a decent after market water temp gauge (like VDO) and get an accurate reading. If it says 180 F but the stock one says 120 F then you know your gauge is bad.


If you don't have a GOOD service manual, like Haynes, for your car, get one. It's invaluable, even for easy stuff like this.

[vbsurfer3001]

Sounds simple & cheap enough to replace. Just go to Pep Boys or whatever parts shop is near you & buy the replacement thermostat, they're cheap like $6-12. Buy the Chilton's book if you're not sure how to replace it. Or try THIS You may need the housing as well.

[Johnny Crab]

What they said^^^^^^^^^^^^^^^^^^^^^^

Those 70's cars(I've had a 73 and 76 Mercury wagon with the 400 V8) had LOTS of room under the hood and the thermostats aren't usually buried like they tend to be now.
I put digital temp gauges on both wagons because all they had were "Idiot" lights.

Is this your engine?

http://cgi.ebay.com/ebaymotors/Plymo...spagenameZWDVW

[Ericman197]

Originally Posted by Johnny Crab

What they said^^^^^^^^^^^^^^^^^^^^^^

Those 70's cars(I've had a 73 and 76 Mercury wagon with the 400 V8) had LOTS of room under the hood and the thermostats aren't usually buried like they tend to be now.
I put digital temp gauges on both wagons because all they had were "Idiot" lights.

Is this your engine?

http://cgi.ebay.com/ebaymotors/Plymo...spagenameZWDVW

That one claims to be a 340, but it has a 400 under the hood. Mine is the 340 with 360 J heads.

So I think I'll go ahead and buy the thermostat, and getting a new water temp gauge sounds like a good idea too just in case.

As for pockets of air, hmm I'm not sure if I checked for that. It might. Would that make the car run cooler though? Or are you saying that it would affect the gauge reading

[HollowBassman]

Originally Posted by Ericman197

...
So what say you, TB? I can post pics later if anyone is interested.

Interested.

[Ericman197]

da grill



cold idling, polluting





bizarre (original) interior




346 (bored over) cubic inch pain in the ass



actually the engine runs and starts up just fine, but there are problems...


old car with intact trunk



So I pulled the car out to take these pics and noticed a few fairly large red drops on the garage floor There were also two small brown drops, but I chalk that up to recently changing the oil and/or my incompetence. I'm taking the car in to the shop right now to have it looked at, I don't want to mess up the transmission myself. Otherwise it runs and drives great!

[BellBottomBlues]

I had a 70 Duster that was totalled last month. When I got the car, it had overheating problems, or wouldn't start in cold weather.

[Ericman197]

Originally Posted by BellBottomBlues

I had a 70 Duster that was totalled last month. When I got the car, it had overheating problems, or wouldn't start in cold weather.

Sorry to hear that! Now that I've learned to finesse the gas pedal just so, Dusty usually starts up on the first try regardless of temperature (Edelbrock 1406 with the electric choke, it's great). However it never gets up to the right temperature, or maybe the gauge is just wack The investigation will continue on Monday when I take it to the mechanic to check out the transmission.

[hbarcat]

Originally Posted by Ericman197

As for pockets of air, hmm I'm not sure if I checked for that. It might. Would that make the car run cooler though? Or are you saying that it would affect the gauge reading

That usually happens when the coolant is drained and replaced. When refilling the coolant, you need to fill the radiator and then run the engine until the thermostat opens and the water pump lets coolant fill the passages in the engine, and then you add more coolant as the level goes down when it begins to fill all the air pockets. You have to continue to add coolant until the level stabilizes at the full mark.

It's unlikely to be your problem but I mentioned it because it can cause unusual temperature fluctuations until corrected, such as running cold for awhile and then suddenly overheating. If you can run the engine when fully warm with the cap off and the coolant level is to the top then the coolant system is full. This is true of older vehicles like yours but not necessarily for newer ones.


I probably don't need to say this, but better safe than sorry:
BE VERY CAREFUL IF THE SYSTEM IS UNDER PRESSURE WHEN OPENING THE CAP. IT CAN SUDDENLY BOIL OR STEAM OUT AND CAUSE SEVERE BURNS.

[Bryan316]

I'd be draining the antifreeze, and flushing the whole coolant system with the garden hose.

Then I'd replace that thermostat.

Then refill coolant, and give it an afternoon to idle, while checking the temp needle.

[Mike N]

Originally Posted by Ericman197

No fan shroud? No wonder it heats up if it's not moving.

[Ericman197]

Originally Posted by Mike N

No fan shroud? No wonder it heats up if it's not moving.

Ahhh, Thanks! Well that's one more mystery solved. I crawled under the car and found that it IS transmission fluid that was leaking... from the power steering pump. I'm kind of hoping that it's just a loose clamp, I'll look into this further tomorrow/Monday.

And here's another thing I only just thought of, that is probably contributing in a major way: the engine fan is running 24/7, even when I just start the car. When the car is off and totally cold, the fan refuses to freewheel if I try to turn it by hand.

Other symptoms: heater core blows lukewarm air all the time, even with the heat all the way up. The only time it ever blew hot was when I let the car idle for a while. So now I'm thinking there may be something weird with the fan clutch, the thermostat, and no fan shroud.

[Mike N]

Originally Posted by Ericman197

Ahhh, Thanks! Well that's one more mystery solved. I crawled under the car and found that it IS transmission fluid that was leaking... from the power steering pump. I'm kind of hoping that it's just a loose clamp, I'll look into this further tomorrow/Monday.

And here's another thing I only just thought of, that is probably contributing in a major way: the engine fan is running 24/7, even when I just start the car. When the car is off and totally cold, the fan refuses to freewheel if I try to turn it by hand.

Other symptoms: heater core blows lukewarm air all the time, even with the heat all the way up. The only time it ever blew hot was when I let the car idle for a while. So now I'm thinking there may be something weird with the fan clutch, the thermostat, and no fan shroud.

Is the fan bolted directly to the waterpump, or does it have a clutch in between? From the look of the picture there isn't a clutch. In that case the fan should spin whenever the engine is running, and you shouldn't be able to turn the fan by hand when it isn't running.

Lukewarm air and a low temp gauge tells me the thermostat is either stuck open or missing.

A new thermostat and a fan shroud should solve some of your problems.

[Ericman197]

I'm going to have the mechanic check the car out tomorrow morning.

I'm having trouble finding a fan shroud that's going to fit, and now I'm starting to think maybe I'd be better off with an electric fan setup

e: wait a minute, the engine fan is driven by the same belt that drives the alternator, so would that mean it has a fan clutch? It's bolted on to something that bolts onto the water pump.

[hbarcat]

Originally Posted by Ericman197

I'm going to have the mechanic check the car out tomorrow morning.

I'm having trouble finding a fan shroud that's going to fit, and now I'm starting to think maybe I'd be better off with an electric fan setup

e: wait a minute, the engine fan is driven by the same belt that drives the alternator, so would that mean it has a fan clutch? It's bolted on to something that bolts onto the water pump.

1) Replace the thermostat.

2) Replace the fan shroud.

3) Don't screw with an electric fan.

[MAJOR METAL]

Be safe eric.

[Ericman197]

Originally Posted by hbarcat

1) Replace the thermostat.

2) Replace the fan shroud.

3) Don't screw with an electric fan.

Do you know of anyone that makes a fan shroud that would fit right? It's a 17" tall, 22" wide Chrysler radiator (numbers are 38086 and 299845). I did a lot of searching but didn't come up with much.

I could go with something like this: http://www.speedwaymotors.com/p/4085...ssemblies.html

although it appears I'd have to weld it together and fabricate the mounts myself. Doable, ish.

[Bryan316]

A couple things.

The fan has no clutch. I don't even think they had clutches for fans in 1975, maybe on the luxury cars like Lincolns.

Contact National Parts Depot (Michigan store:Toll-Free 800-521-6104) and ask them for help, if any of the other models shared the same fan shroud. It's common that the exact same parts from a completely different Chrysler car will fit. They are all car junkies over there, they'll either know it or know someone who will know it. If not... EBAY.

Power Steering Pump.... okay, no exceptions no excuses here... replace the hoses leading to and from your pump. New fittings, new rubber, new everything. And teflon tape those threads! And inspect your PS control valve as well.

Lukewarm heater air also says to me the thermostat. Also, maybe check the hoses leading to your heater core. Plugged hoses? Heater core plugged up too?

[Ericman197]

Originally Posted by Bryan316

A couple things.

The fan has no clutch. I don't even think they had clutches for fans in 1975, maybe on the luxury cars like Lincolns.

Contact National Parts Depot (Michigan store:Toll-Free 800-521-6104) and ask them for help, if any of the other models shared the same fan shroud. It's common that the exact same parts from a completely different Chrysler car will fit. They are all car junkies over there, they'll either know it or know someone who will know it. If not... EBAY.

Power Steering Pump.... okay, no exceptions no excuses here... replace the hoses leading to and from your pump. New fittings, new rubber, new everything. And teflon tape those threads! And inspect your PS control valve as well.

Lukewarm heater air also says to me the thermostat. Also, maybe check the hoses leading to your heater core. Plugged hoses? Heater core plugged up too?

I just thought it might have a clutch because it's highly modified, but yeah I guess not. I'll have to deal with that issue later on.

The heater core works because I know when I left the car running it blew VERY hot air!

Unfortunately I didn't get a chance to do anything today, but on the to-do list is DEFINITELY to get the p/s checked out, and to buy a fan shroud.

Now I'm thinking I could and should get the thermostat replaced, but does it matter that much if the engine runs at 130 F? I'm thinking I should get it fixed so the oil gets up to temp., better emissions/fuel economy etc., but my dad is giving me the "if it ain't broke don't fix it" line... eh, it's like a $5 part...

e: Called the parts place, no dice (they don't do mopar)

so my fan shroud choices now are either a generic and perhaps crappy one like this:

http://cgi.ebay.com/ebaymotors/Chrom...spagenameZWDVW

or an original/reproduction for $100ish

what do you guys think