Thermostat 195F, when driving engine is always 150F

[kikkegek]

guys,

I have a strange problem I wanna ask your opinion on and experience.

I have a 350 small block with a 195F thermostat.
I have an electric fan that kicks on at 200F and stops at 180F.

for some reason my engine warms up to 150F, but max 160F when driving. Even at traffic lights it seems to hang around that temperature. Only when I sit at a traffic light for a couple of minutes or let it idle for some time the temperatures to the 200F and the e-fan kicks in and cools it down.

as soon as I start driving again, town or highway, the temperature goes down to 150F again...

isnt that strange if there is a 195F thermostat in there?

I already checked the thermostat and put it in water boiled it and:

at 175F it opens...you can see that at 55seconds into the video, there's a bubble coming from the bottom of the thermostat.

at 2 minutes the water boils and the thermostat is wide open.

when it cools down the thermostat is fully closed at 175F

should it start opening at 175F?

heres the video on Youtube:

Thermostat test 195F - YouTube

[Gyawo]

Do you have the proper radiator for the vehicle/engine? Obviously the T-stat isn't sticking open so that isn't the case. Proper operating temp is around the 180 mark, 150 is a touch cool.

[foamypirate]

I find that a typical thermostat opens about 5-10* AFTER it's rated temperature. You may want to try another one.

[jrsavoie]

get a GM, AC Delco or Stewart. I've hd nothing but problems with any other aftermarket thermostats

[gchemist]

You live in a cold climate. The thermostat is probably working fine. The cold climate may affect the sensor output. Watch carefully when you start it in the morning. The temps should go up to 200 then drop quick when the thermostat opens. After the thermostat opens, the temps gauge may not go back up to normal ops again. If it's too cold, use a 205 thermostat. The cooling fan will keep it cool at idle/traffic. Once the truck is moving, the radiator alone will keep it cool. An engine can run cool. It's oil temperature that is a concern. If oil is not hot enough, poor oiling occurs.

[oldschool18]

my truck was the same way, I put the extra core rad in it and it wouldnt get hot, put cardboard in front of the rad in the summer and still nothing. and in the winter I had no heat, i put a 160 thermostat in it and i got better heat....not great heat...but better heat

[wilkin250r]

You're right, it does seem strange. Are you actually having problems, or are you just trying to solve the mystery? Are you doing all this testing because your heater isn't working the way you want it to?

Spending all day draining radiator fluid over and over isn't really my idea of fun, but thermostats generally aren't that expensive. I would go buy several varieties, different brands, different temperature ratings, and do the same boiling water test. When you find one that opens up later, try throwing that in and see how your cooling system responds.

[wilkin250r]

Originally Posted by oldschool18

my truck was the same way, I put the extra core rad in it and it wouldnt get hot, put cardboard in front of the rad in the summer and still nothing. and in the winter I had no heat, i put a 160 thermostat in it and i got better heat....not great heat...but better heat

I'm thinking you may have a routing problem. I'm assuming your heater hose comes out of the intake manifold, like most of ours, but then I'm assuming it returns back to the radiator? You would likely get better heat if you returned it directly back to the water pump, especially if you coupled it with a higher-temp thermostat.

[kikkegek]

okay guys, thanks for all the response. Some answers then to questions:

QGyawo: radiator: jep, right size, although the heavy duty version (so rather big for our use)

@gchemist: nope, engine warms up to 150F and stays there, unless I let it idle for a long time at a traffic light or just when parked. So when I cold start it, we usually hit the highway within 1.5 miles. then within 3 miles it will be at 150-155F and stay there, untill we leave the highway after about 7-8 miles. then we drive through the city for about 2 miles and not even then it will go much higher...only when we reach the parking lot and dont turn it off immediately it will reach 00F and the e-fan will turn on.

shown temperature:
I am guessing it is 150F because I already opened up a topic before on these temp gauges that come factory installed. they have a strange range. check it out:


since I checked my thermostat. And because it starts opening at 175F and is also when cooling down fully closed at 175F, you'd expect the blind marker at the left side of the 210 not to be the 155F mark, but the 175F mark, because of that!!!

I know my temp gauge reads the right temperature, because I have green LED in my dash that tells me when my e-fan is ON. and it kicks ON as soon as the needle on my temp gauge gets very close to the 210F mark...




sooo....that being said...I am really curious where the needle is at YOUR GAUGE when you have a 180F thermostat in your car? anybody got a 180F thermostat and can check where their needle sits?

[Pyrotechnic]

I wouldn't trust the stock gauge, not with the life of the motor.

I like to run a true mechanical aftermarket gauge in addition to the stock gauge, they are accurate and not too expensive, and there's no guessing about the temperature when you look at it.

[1BadAction]

You're basing this on the range of the stock gauge? They are notorious for reading odd - My k5 would swing from just above the "150" mark, all the way up to just under 210, then back down. It was only a 15 degree or so swing on my autometer, but took nearly 1/4 of the stock gauge sweep. You could literally watch the thermostat working.

Get a good gauge on it, take a mental note of where the stock gauge is at your operating temp range, and just keep an eye on the stock gauge for reference.

[hatzie]

A good 195 thermostat should be visibly open at 200-205 degrees not 175. Sounds like you have a 165 degree thermostat.

[nerphin]

Originally Posted by kikkegek

okay guys, thanks for all the response. Some answers then to questions:



sooo....that being said...I am really curious where the needle is at YOUR GAUGE when you have a 180F thermostat in your car? anybody got a 180F thermostat and can check where their needle sits?

I run a 180 degree stat. It runs at the line you have marked as 175.

Also, I measured the temperature at the thermostat housing with an infrared handheld thermometer and it reads 180 degrees when the water is flowing.

If I were you, I would get a new stat.

[GMC Guy]

i run a mechanical gauge in addition to the stock gauge. at normal operating temp the stock gauge never reads past the first line, and the mechanical gauge reads right at like 190. plus with the mechanical unit you can see the temp rise and then drop back down when the t-stat opens. oh and i run a 195* thermostat

[kikkegek]

thanks guys. I am probably gonna change out my thermostat then..

I now got this one in it


I need to change the coolant anyway, because I head the heads and gaskets replaced...so while changing the coolant I'll change the thermostat too..

thanks, I'll report back when I am done....great info!

[kikkegek]

my wife just came back froma drive and I checked temps: gauge left mark 155F? top of intakemanifold near thermostat housing 190F, top right of radiator 190F and bottom left of radiator 140F...so thermostat is fine, gauge is not...thanks guys...

[78 Chevyrado]

Probably the temp sensor for the gauge going bad.

I had to search around to get one that was built correctly for mine.

Bad quality control.. I bought 2 new ones, one made the gauge read at the 1/4 mark, and one sensor made it read at the 3/4 mark when at full temp. so i got the resistance of both and found halfway between them and took my meter to the parts store and had to check 7 or 8 of them before I found one with the proper resistance, which will make the gauge read right, which is somewhere around straight up.

[kikkegek]

Originally Posted by 78 Chevyrado

Probably the temp sensor for the gauge going bad.

I had to search around to get one that was built correctly for mine.

Bad quality control.. I bought 2 new ones, one made the gauge read at the 1/4 mark, and one sensor made it read at the 3/4 mark when at full temp. so i got the resistance of both and found halfway between them and took my meter to the parts store and had to check 7 or 8 of them before I found one with the proper resistance, which will make the gauge read right, which is somewhere around straight up.

yep! I cant find it anymore, but I read somewhere that these senders have a accuracy of 6-15%....

I still dont understand though why my gauge correctly shows 200F when my e-fan kicks in...My e-fan turns off when the temp hits 185F...and that is pretty close to the mark on the left of 210F on my gauge...

well....I'll do some more testing, but I guess I have to give up on my gauge

[1BadAction]

Originally Posted by kikkegek

I still dont understand though why my gauge correctly shows 200F when my e-fan kicks in...My e-fan turns off when the temp hits 185F...and that is pretty close to the mark on the left of 210F on my gauge...

It's just the way the stepper motor in the gauge swings compared to the marks on the gauge face. Might be due to age, but it may also be just the way that particular design works.

[tkeduk8r]

I actually had a similar problem with my 74 c10 when I swapped over to gauges from idiot light about 10 years ago. I had a new ACDelco temp sensor, but my 100-250 gauge didnt read where I wanted it too, (IIRC it read about 220 deg, but my pyrometer measured the correct 190 under the hood)... Here's how I solved the problem. I first measured the change in resistance from sensor to ground as the temp sensor warmed up. I used that range of resistances to pick out a small potentiometer (think volume control knob on a radio) that I could run in series between the gauge and sensor. This allowed me to adjust the resistance with the potentiometer and thus make the gauge read what the engine temp actualy was. Then I removed the "pot" from the circuit, measured the resistance, and returned to the "shack" to by a fixed resistor that I soldered in series with gague and sensor. Hope that wasnt too confusing, but I was out only about 5 bucks for the potentiometer and resistor and the gas to get back and forth from Radio Shack.

--Mike

[kikkegek]

okay, did some more testing this morning. when the engine is 180F (thermostat house and waterpump) then the gauge shows just a little over the left marker..then as the engine temperature increases it slowly moves towards the 210 marker and just before it my e-fan kicks in...(200F)...then it cools down to 185F...which is closer to the left marker then the 210F...so in my case the left marker represents about 175F...now that I know, I dont have to worry anymore about engine temperature...because I now know what my gauge reads...

this were my readings. I would have to do some more readings with a helper to see what the reading left of the 180F gives me...but for now I am fine.

I also noticed that my radiator stayed at 150-160F while my engine was measuring 180-200F. So the thermostat wasnt opening too soon, otherwise the radiator would have measured the same temperature at the top right...

[Pyrotechnic]

http://www.summitracing.com/parts/ATM-2392/?rtype=10

A very cheap insurance policy if you ask me.

[kikkegek]

Originally Posted by Pyrotechnic

http://www.summitracing.com/parts/ATM-2392/?rtype=10

A very cheap insurance policy if you ask me.

it is indeed. I might consider that. I have a faulty oil pressure sender and I am waiting for a new sender. If that also doesnt work out. then I'll buy this thing and be done with it forever.

thanks man!

[kikkegek]

I saw I forgot to post my recent discovery here...

friend of mine pointed me to these nice aftermarket gauges for a nice price, including senders and mounting materials.

http://www.mcgillmotorsports.co.uk/

they are in England, but that is close to me, so shipping is cheap.

here's some nice videos:
http://youtu.be/SP7bBr-7Nqw
http://youtu.be/nu8C7y9ZBx0

I ordered the oil pressure and water temperature for now, but if I like them I will also replace the VOLT and tach with them to get the complete set for my car.

[Weasel Diesel]

Yea, I'm re-doing my dash guages too and going to mechanical. The volt guage reads 12 volts when system voltage is 13.5, Temperature reads 210 all the time, Oil pressure... what oil pressure ( We don't need no stinking oil )?, I can't get a speeding ticket because no matter what it dont go no higher than 25 mph, and my fuel milage is fantastic as I have been driving it daily for 6 months and it hasnt moved off 2/3 tank !!