running too cool?

[landyacht318]

What would you expect the thermostat housing to read on a laser/IR thermometer after the engine is up to full temp?

I noticed my dash gauge was not climbing up to it's normal range. I hit the thermostat housing at full temp with the laser and got only 165f. The oil pan was 195f.

I flushed the radiator, replaced the thermostat and there is no change. The fan is running it's normal speeds, and I'm currently driving it in ambient temps of 60 to 70. I got approximately 50/50 coolant mix.

I can drive it 10 miles and take off the radiator cap with no overspill.
The engine is running great and the exhaust doesn't smell rich, but I suspect my fuel economy has dropped, hard to tell without much highway driving.

Any reccomendations on an aftermarket temp gauge?

I do have a small coolant leak near the just replaced thermostat bypass hose. Think there is any relation?

TIA

[Dodgevanman]

What temp. thermostat are you using?

[alloro]

I hit the thermostat housing at full temp with the laser and got only 165f.

This reading would be acceptable if the t-stat was closed at the time of the reading. Making sure the t-stat is open and coolant is flowing will give you a higher reading. Also, turn your heater control knob all the way to cool so that the vacuum closes the heater hose valve.

[landyacht318]

I'm using a Stant 195 degree thermostat and getting it to open seems to be the problem. It won't open when idleing for 20 minutes. There was still air in the upper radiator hose after driving it 5 miles.
I'm not gonna waste any more gas trying to get my gauge to read normal. I figure it's been running the same temp for a while and the oe gauge has gone haywire.

[DANVAN]

I would guess that the stat is staying open and causing the cool temp. ??

Try the ir temp gauge on the radiator to see the temp there, pick different spots on the rad, top and bottom.

[alloro]

Or temporarily put a piece of cardboard in front of the radiator to stop the airflow.

[landyacht318]

I thought the first 195 thermostat was stuck open, it wasn't. I did cover the front grill entirely, but not directly on the radiator. It still didn't want to open till I held the rpms up for 30 seconds or so, and then not enough to overflow the radiator with the cap off.

The highest temp I got off the top of the radiator is 197 while at the bottom it was 136. This fell quickly after it idled a little.

[landyacht318]

I'm dredging up this old thread of mine because the problem is still there. I just passed a smog test, but the hydrocarbons were on the high side. The tech said it was running too cool. He said maybee advance the timing.

I've never been good at reading OHMs on my DVM. Could somebody Tell me what setting I should have the meter on, and what the readings should be on my DVM when testing my CTS when cold and HOT?


Also I don't believe my coolant mixture is 50/50 anymore. Would a 65/35 water/coolant ratio cause that much cooler running?

Will advancing the timing cause it to run warmer?

And an unrelated note. Here in California they are checking all pre '96 vehicles for leaking fuel systems. They pump 32 psi into the tank and see how much it drops. I had mine pretested yesterday, and it passed. Today on the official check at a test only center, they did not bother with that, or check the timing.

[alloro]

The resistance should range from 18,000 ohms at 50 degrees down to 600 ohm at 192 degrees. (The resistance goes down as the coolant heats up.) The AF to water ratio will not effect the temperature of the coolant as long as the coolant isn't boiling from not having enough AF in the mix.

Advancing the timing will make the engine run hotter and will also increase the hydrocarbon reading.

If the engine isn't not coming up to temperature, either the t-stat is no good (stuck open) or coolant is leaking past the t-stat. High hydrocarbons can be the result of low engine temperature, a vacuum leak, excessive carbon in the cylinders, or a bad catalytic converter.

[B-300]

Coolant ratio wouldn't affect the temp that much.
32 PSI in the fuel system is enough to break a weak tank.... I'm glad I'm pre smog.
Lean misfire will also cause high HC as well.
As for low temp a thermostat causing the engine to run cool will also cause the PCM to enrich the Air-Fuel ratio causing it to burn cooler.

[landyacht318]

Perhaps I misunderstood the tech yesterday. The pressure from the nitrogen tank to the testing machine had to be 32 psi. Of that I'm sure. I don't know how much of that PSI the test machine allows into the fuel system. I was also worried about 32 psi. I imagined my tank rupturing and 16 gallons of gas leaking on the floor.

Today at the official test, I saw the tech on the next bay was testing a old pre obdII cherokee, but the guy working on mine didn't bother.

So 16 months ago when I first saw my temp gauge not rise to normal levels I replaced the stant 195 with another stant 195 thinking it was stuck open. There was no change. I doubt coolant is getting past the T stat. And unless there are a bunch of counterfeit Stant thermostats out there, it is unlikely that 2 separate 195 degree stats were equally inaccurate.

I more or less assumed the 1 wire sensor for the gauge cluster was inaccurate, and adjusted to the new lower readings.

So now I'm thinking that the 2 wire CTS is out of whack. If it is, could this inaccurate read make the engine run so much richer that it runs 10 to 15 degrees cooler? But no so rich that I would fail an emissions test?

It will be 2 years before I have to pass another test, but If I'm running rich, and too cool, I'd like to sort it out.

Too rich and too cool. Yep that's me.:crazy::crazy:

[alloro]

So now I'm thinking that the 2 wire CTS is out of whack. If it is, could this inaccurate read make the engine run so much richer that it runs 10 to 15 degrees cooler? But no so rich that I would fail an emissions test?

Yes, if the 2-wire CTS is out of whack the engine will run rich. But that sensor has nothing to do with the dash gauge. Have you tried sticking a mechanical thermostat into the radiator fill hole to get a temperature reading?

[landyacht318]

I do not have a mechanical gauge, only the laser/ Ir thermometer, and it does not seem to be accurate on liquids. Such as a beer so cold it has ice crystals in it will read 53 degrees.

Mmmmm, beer. Chk,fweeep, gurgle gurgle gurgle, ahhhhh.

Alloro, I have to good naturedly bust your balls for a moment. Please don't take offense. I value your input.
Are you a politician?
You seem to reply to a question without really answering.

My question implied that I am aware that an out of whack CTS can cause the engine to run rich.

My question was, can a rich running engine cause the engine to run 10 to 15 degrees cooler?



I'm considering getting a real water temp gauge in place of the stock one, because if it is as accurate as my stock oil pressure gauge, it is not accurate at all.

Perhaps I am not running too cool and it is running rich for other reasons.

I will take some OHM readings on the CTS soon at different temps and post the results.

[alloro]

Alloro, I have to good naturedly bust your balls for a moment.

You seem to reply to a question without really answering.

So you want to have a ball busting contest...hmm. :)

The reason I didn't spell out an answer to your question is because anyone that ever turned a wrench knows a lean running engine runs hot, while a rich running engine runs cool. So by reaffirming your remark about a potential problem with the CTS causing the engine to run rich; I gave you enough credit to extrapolate the rest of the answer yourself. Apparently I was wrong to do so. :5191Moon-thumb: Your turn. :popcorn:

BTW - This might be handy for you:
http://race-mart.storesecured.com/items/products/mr~gasket/MRG2471R-detail.htm

[landyacht318]

I don't recall anything about a contest. :help:

I am aware of the lean hot, rich cool scenario. Mine was a question of degree. Is a rich running engine gonna run 15 degrees cooler, or is the variation less or more?

There is also a chicken or the egg conundrum here. It running cool because it's running rich, or is it running rich because it's running cool.


On 11/20/07: It tested@ 15mph.
@1419 rpm (13.9% co2) (1.5%o2) (40 ppm HC) (0.05 % CO) ( 87 ppm NO)
On 06/04/09: It tested @ 15mph
@1415 rpm (12.9% co2) (2.4%o2) (121 ppm HC) ( 0.19% co) (286 ppm NO)

Boths tests were at the same facility.
122 PPM of HC is the max allowed.

Thanks for your timely replies and your confidence in my extrapolation abilities. Now answer the question oh eloquent master wrench turner! :worthy:

Chicken or egg?
+ or - 15 degrees possible?

BTW thanks for the link. Looks a lot easier and cheaper than a new analog dash mounted gauge.

[alloro]

A rich running engine will have a cooler combustion temperature, but not a cooler coolant temperature. For example, if normal combustion is 2,000 degrees, but is only 1,800 degrees due to a rich condition, the difference is irrelevant to the coolant which is only at 192 degrees. The coolant temperature is regulated by the t-stat, which is not supposed open until the temperature of the coolant is up around 192 degrees.

[landyacht318]

That really should have been obvious to me.

Thanks for the enlightenment.

[alloro]

That really should have been obvious to me.


I thought I already said that a couple of posts up. :nutkick: :)

[B-300]

Your smog checks were done at different times of the year... fall and summer. This is enough to see different readings since the fuel injection is speed density and not mass-air flow which can compensate for different air density due to barometric and temperature changes.
With oil temperature at 195 f the engine is warmed up.... Air moving over the theromstat housing by th fan could lower the temperature the IR gun reads at the surface of the housing.
The smallest amount of corrosion at the one wire sender will increase the resistance causing it to read low. The 2 wire sensors have can fail when the thermistor inside doesn't have good thermal conductivity with the outer boss.
Smog # of increased HC, NOX suggest a lean mixture but increase CO suggests a rich mixture... I think it's possible the cat con. is weak. I had similar readings with my '78 over 10 years ago with a burn't out cat con running on 7 cylinders and did a valve job and and put on a new cat con. had # on the CO an HC about half of your 1st test.

[landyacht318]

Your smog checks were done at different times of the year... fall and summer.
Smog # of increased HC, NOX suggest a lean mixture but increase CO suggests a rich mixture... I think it's possible the cat con. is weak.

Both tests were taken in S California coastal area in humid overcast conditions (marine layer) with the summer test maybe being 5 degrees warmer.

But my Cat con is at least 4 years old now, maybe 5.

And the first test was taken the day after I arrived in California after leaving Florida 3 days previous and using fuel I bought in Arizona.

I've only put a little over 4k miles on the van between the tests, mostly in 5 mile increments.

[B-300]

This new info suggests you should change oil before a smog check when doing stop and go driving. (I forgot to mention that in my last post) Also were I live (inland of the coast) it's usually raining by Nov (65f) and about 85f in June and dry.

[landyacht318]

Before this last smog test I:
- changed the oil using synthetic.
- removed and cleaned throttle body
- removed and cleaned/ unstuck the EGR's pintle
- cleaned and inspected SP wires
- cleaned the brass contacts in Distributor
- cleaned the K&N
- replace gas cap
- run Seafoam through the tank for the last 350 miles and during the test with 87 octane.


The van was as warm as it currently gets, before and during the test
They do the test at 15 and 25 mph. It was cleaner at 25 mph
..............co2.....o2....hc.....c0..... no
15 mph...12.9....2.4....121...0.19...286
25 mph...13.2....2.1.....88....0.04...223

[landyacht318]

Got around to checking the CTS.

IR thermometer aimed at base of cts from 2 inches away
DVM on 20k ohm setting
@ 68.5 degs read was 11.92, which I'm assuming is 11,920.
@ 192.5 degs read was 0.71 which I'm assuming is 710

The Haynes manual says at 50 to 80 f ..... 17,900 to 10,800 ohms
The Haynes manual says @180 to 200f .... 1,170 to 820 ohms

So at temp, the resistance is a little low according the the Haynes manual.

On the second, at temp reading, the dash gauge showed it's normal full temp but the oil pressure indicated It was not as hot/thin as it gets.

So the computer thinks it is running hotter than it really is, correct?
What is the ECM's response to this slightly low 710 reading?

[alloro]

My manual say 18K ohms at 50 degrees and 600 ohms at full temperature for the CTS.

[landyacht318]

what year is your Van?

I see that Rockauto lists different CTS part numbers for a 1999 vs an 1989.
The threads look to be different sizes. Perhaps the resistance values are different as well.

Will my reading be inaccurate if taken 1 minute after shutting off the engine?

[alloro]

Mine is a 2000, V6 3.9L

[landyacht318]

2000 cts
http://info.rockauto.com/getimage/getimage.php?imagekey=932439&imageurl=http%3A//info.rockauto.com/Airtex/5S1035.jpg

1989 cts
http://info.rockauto.com/getimage/getimage.php?imagekey=929467&imageurl=http%3A//info.rockauto.com/Airtex/5S1021.jpg

Not hard to imagine the values might be different.

[97B2500CCV]

@ 68.5 degs read was 11.92, which I'm assuming is 11,920.
@ 192.5 degs read was 0.71 which I'm assuming is 710

The Haynes manual says at 50 to 80 f ..... 17,900 to 10,800 ohms
The Haynes manual says @180 to 200f .... 1,170 to 820 ohms

So at temp, the resistance is a little low according the the Haynes manual.



With those readings I would replace the sensor. It appears that the PCM thinks the engine is at a hotter temperature than it is wither cold or hot.

[landyacht318]

Does anybody know if the ECM on an '89 is constantly adjusting the A/F ratio depending on inputs from the CTS?

Or Does the resistance within the sensor pass a threshhold where the ECM then goes into a default A/F ratio?

[alloro]

It constantly adjusts it based not only on the CTS but various other sensors as well.

[VanMoreSon]

My FSM for a '91 lists 700 to 1000 ohms at 200degs. At 70degs. it's 7k to 13K ohms. The section in the Haynes manual I believe is for the '92-up MPFI versions. Under the Emissions section, the FSM says the CTS "operates the air switching solenoid". Under the ignition and fuel sections it states that "varying inputs are sent to the ECM to provide different spark advance curves for cold and warm operating temps" and also "gives richer air/fuel mixture for cold engines".