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Engine temp stays cold

52K views 38 replies 10 participants last post by  Shut-Trip 
#1 ·
Well another problem for me. 1995 hb 4x4 2.4. My temp on my truck stays cold and only sometimes rises above the cold maybe to slightly a quarter of a tank mark. I have replaced

new coolant switch/sensor
new radiator
new water pump
new thermostat
flush heater core

I have grounded the wire for temp and my needle goes to high. Have bleed air out of the system with the screw on intake, Just don't know what else to do. Now I live in smoky mtns driving on highways the temp just comes up to the end of the cold mark. When going up mtn roads the temp will rise to the quarter tank mark or just tad under it. but soon as back on highway it drops back down. Heat works but just enough to break the chill but when temp gets to the quarter mark it will run you out. Does anyone have some other ideals?
 
#4 ·
It's a stat from autozone. But the one I took out was same thing I bought few years ago. It has ran fine for years. But thats what I was thinking also that it opens to soon. Just don't understand why stopped working unless it was the new water pump and radiator. When looking in the radiator it looks like a river flowing circulating good.
 
#7 ·
An oxygen sensor with a shift that would cause the ECM to increase the fuel injector duration to make it run richer, might cause slightly cooler combustion temperatures, but not to the point where the engine coolant would be adversely affected to the point where the coolant would run that cold. As far as the 60,000 mile oxygen sensor interval, there are very few vehicles on the road that need the oxygen sensor replaced at that time. I remember in the early 80's, Nissan had a sensor light that needed to be reset every 30,000 miles to remind that the oxygen sensor needed to be checked. There are plenty of vehicles on the road with well over 100,000 miles on their oxygen sensors and they work perfectly fine; I had over 200,000 on my 97 Hardbody's before I sold it. I'm not saying it's not worth checking the operation, but I just don't see it causing the OP's coolant problem.
 
#8 ·
possibly the wire to the sensor is bad, when you ground the wire for the sensor and the gauge went fully up, shows the wire you grounded it with works, but the actual wire to the sensor may be bad, I would check the temp with a infrared thermometer to see if it is reading what the gauge is showing.

Since the heat works good when the gauge goes near the 1/4 mark, than possibly the engine is running/cooling properly but the gauge is reading low.
 
#9 ·
"when you ground the wire for the sensor and the gauge went fully up, shows the wire you grounded it with works, but the actual wire to the sensor may be bad"

That statement contradicts itself. There is only one wire in the circuit between the gauge and the temperature sensor. The sensor is a variable resistor to ground. When you unplug the wire at the sensor and ground it, you are providing full ground for the circuit, which should cause the gauge to go to full hot. This test lets you know the wire circuit is good. If the wire was broken or "open," the gauge would not read at all. If the wire was shorted somewhere, the gauge would read full hot all of the time. If there was excessive resistance, like corrosion, in the wire, the gauge would not go to full hot, it would read something less, dependent on how much resistance is in the wire.
 
#10 ·
I stand corrected, thanks
 
#12 ·
I bought oem thermostat should be in today by time I get home. So going try get it put in today. As far as o2 sensor it has been replaced but probably have over 60k on it by now. But wouldn't o2 cause a code? I'm going to check the coolant temp after I drive it for a while to know a number on it. How hot should coolant be? My mileage on gas is about the same most the times but few times it is a lot worse. I keep up with it a lot. I get on avg about 150 miles on 9 gallons. Which puts me at quarter tank and 16mpg. Never run it to E. But few times sense this problem I have gotten as low as 12.5mpg driving same 150 miles but taking 12 gallons to fill up. I reset trip counter every fill up cause my cluster had stopped working for good while before I replaced it.
 
#14 ·
If you had a "lazy" O2 sensor, there would not be a code but the ECM would still tweak the amount of fuel it is adding to get the mixture back where it thought it should be.



Since yours is not that old, I'd look at the connector for that O2 sensor. The wire should route around the transmission and up into the engine compartment, just behind the battery. Pull the connector apart, make sure all of the wires look good, no corrosion, etc. then plug it back in.

The CEL should only turn ON under a few conditions:



If that does not make the Check Engine Light (CEL) go out after a few miles, I'd suggest Ohming the injectors.



You could also check the resistance across the thermostat temperature sensor.

 
#16 ·
So I changed out thermostat with oem one and it didn't make a difference. And I did check the clutch fan and it is fine. I didn't get to check coolant temp yet. And for my check engine light that is code 32 on egr. Another problem I have been working on eliminating. But will test o2 and check injector here in few days going have some long days at work rest of this week.
 
#20 ·
After the engine is fully warmed up, check the bottom radiator hose to see if it's hot; also turn on the heater inside the truck to see if it blows out hot air. If so, then the temperature gauge or connections or the sending sensor may be bad. Also make sure the coolant system is fully purged of air.
 
#17 ·
Checking the EGR valve isn't too hard.

Check that it holds some vacuum:



Then, check that the diaphragm moves in and out freely:



Mine was fine, but cleaning it up still made a noticeable difference in my engine idle.

You can clean the EGR, but it takes a really big wrench to get it off - metric 26, or something like that.

If you can get it off, squirt a bunch of Carb Cleaner into it, and work the plunger around.

Usually it gets clogged up over the years with carbon deposits, so a little Carb Cleaner will work wonders on it.

Of course, I also just like this picture:

 
#18 ·
Thanks for these pics few of these I have not tried. I have taken it off and cleaned it up and the bpt early this year when I put new head on my truck. I also changed all my vacuum hoses out. It's just weird cause the light comes on for while then goes off. Some weeks if can go days and not see check engine light come on then it may come on and stay on for few days or just come on hour or so then go off. But it's always a code 32.
 
#19 ·
For Code 32, there are 3 pages of diagnostics in the 1994 Service Manual, pages EF & EC-239 to page EF & EC-241.

It shows where to check for vacuum leaks, how to inspect the EGR valve, EGRC-BPT valve and EGR temperature sensor, EGRC-solenoid valve, what pins to check on the ECU, etc.

I can't post a link, but I can post the pic of where to find it:



Look for the EC file.

This forum will not let you post the word nico and club as one word.
 
#24 ·
I think the main issue is whether the coolant is actually running colder than it should or is the gauge reading incorrectly. Use a thermometer to measure the heater output at the vent with the engine fully warmed up and heater set to maximum "hot" setting. The heat vent at the floor should be putting out air at a temperature of around 130-140 degrees F. Run the engine at speed with the cap off until you see the coolant cycling; thermometer should read about 170+ degrees F. If the temperatures are in that range, the sender is new and the circuit tested good, it would seem that the accuracy of the gauge is off. You may want to pull the cluster and double-check the resistance of the wire between the gauge and the sender with an ohmmeter.
If the thermometer readings are significantly colder than those temps, it's a coolant system issue, and not the gauge/sender/circuit.
 
#25 ·
Yes, to the main issue. the man said he sees the coolant flowing in the radiator with
the cap off. that's not a thermostat controlled flow! It's a bypass thermostat which
has a disc on the engine side to stop bypass during thermostat regulation of temp.
the thermostat is NOT closing. As for the gauge/sender issue, the gauge is calibrated
for a certain temperature reading correlated to the recommended thermostat temp..
they go sour sometimes and will read colder or hotter. the important factor is the
engine tempertaure which is simply the thermostat, excepting engine failures.
I use a temp. gun to check hose/coolant temps., however simply done, the upper
radiator hose should become min. 160 degrees during thermostat opening. that's
the easy way to tell. best to check while idling, cap off is fine. working system will
pulse coolant up/down not "river flow". keep it simple. good luck.
 
#26 ·
We'll I bleed the radiator system again still had some air coming out did it for an hour or longer. So after I felt that I had all the air out I rev the motor up to about 2k held for a min or so, this is with my funnel still in radiator full of coolant. So when came back around I notice very small bubble and coolant started looking frothy or like beer suds. So I was thinking bad head gasket getting combustion gas in coolant. Went and got block tester. Got home pop hood open cap and it's has an inch or so of beer suds. I tested it with block test and it was negative. So I got me a temp gun and these are my temps.

Radiator coolant from the fill hole. Low 98 highest 115
Top hose. 115
Engine head front 134 back 218
Therm housing 115
Exhaust manifold 325 by head by o2 sensor 502
Heat on inside truck low 90s longer I held gun there maxed out at 120.3

So open to any other things to try.
 
#29 ·
Suds?



Suds?
When I heard your temp was low I first thought your thermostat was in the wrong way and all-ways open from the force. Then I thought some one put a rebuilt radiator in your car and it was too good. Now suds makes me think some one put windshield washer fluid in buy mistake. It does sound like air too. But suds?
Is this with new fluid? You can't pump suds. Is your electric fan shutting off? Suds, like soap suds? I would change the fluid / flush with water then refill and if the suds come back I would think head gasket also.
 
#27 ·
Just little update on this. I ended up blocking 2 sides of my radiator with cardboard only leaving the center exposed. My temp now rises up to slightly under the quarter tank mark on cold days and on warmer days a little pass quarter mark while driving to half tank make when sitting and idling. But no over heating.
 
#30 ·
If it's a Hardbody, it doesn't have an electric fan unless someone installed an aftermarket fan. Also, there's no way to make a radiator "too good." Regardless of how cool the coolant gets in the radiator, the coolant in the block will still need to get to the temperature setting of the thermostat before the thermostat opens to circulate the coolant. The coolant in the heater core should be the same temperature that is in the block. An improperly installed thermostat crossed my mind; it still sounds like a thermostat issue. Even washer fluid shouldn't have that much of an affect on the temperature if it were installed in place of coolant, as it is composed of distilled water and isopropanol. A head gasket failure could create air pockets, but the combustion gases should help to raise the temperature of the coolant and will usually cause overheating.
 
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