96 4.3 Engine Won't Heat Up

[reelamin]

First post here and love this site. I have a huge list started and already ordered some upgrade parts due to the information here. I did a search and can not find what I'm looking for. I am open to those with better search skills or any input.

I just picked up a 96 with a 3.4, and noticed the heater was luke warm. (225K but its what I could afford) I did all the heater checks, and finally checked the coolant temp. Using a infrared thermomter I checked the engine, and it is not heating up. I am guessing stuck open thermostat, but I can not see any water circulating in the radiator. I can usually see water moving on other vehicles I have owned. But this is my first 3.4 Toyota.

I am open to any ideas. Here are the temps I got after pulling into the shop off the highway.

Top radiator hose near the block clamp = 125f
Top of radiator = 137f
Bottom of radiator = 72f
Bottom Radiator Hose = 83f
Thermostat Cap = 87f

If I let it sit and idle in the shop while checking things the temp rises but still not super hot. The heater blows hotter also, so it seems the main culprit is the fluid temp.

Top Hose = 150
radiator = 170
Bottom Hose = 88
Cap = 100

I also checked the valve covers and intake near the block etc. Most were reading at 150 and the highest I could find was 180 (down inside the passenger side space between intake and valve cover near the head)

 

[scrap metal]

What does the temp gauge on the dash show?

Have you topped off your coolant? Should be able to see water in the radiator. If your tstat was stuck open you would always see water flowing.



I'm guessing maybe you don't even have a tstat installed.

 

[wake_rider]

Something to consider is that you also have not enough fluid to cirulate. When you run out of coolant (cracked radiator or something more dubious), your temperature gauge can show cool temps because it is measuring the air temp rather than the coolant temp, and it will show a greatly reduced temperature comparatively to where the engine is actually running.

I have seen this happen when I tagged an alligator snapping turtle on the highway with a lowered Prelude (not good for the car, but downright explosive for the turtle). It busted the radiator and as the temp began to climb, it suddenly dropped to show the needle below cold. That's when I knew that I could putt it along no further (I was just trying to limp it back into town), and would have to settle for finding a tow in the morning.

I cannot tell by your temp readings with your infrared thermometer whether or not this is your case, but just be sure to have your coolant topped off and see if you can witness any flow through the radiator after being certain that you are filled up on fluid. After that, replace the thermostat. Easy job.

 

[gamefreakgc]

Something to consider is that you also have not enough fluid to cirulate. When you run out of coolant (cracked radiator or something more dubious), your temperature gauge can show cool temps because it is measuring the air temp rather than the coolant temp, and it will show a greatly reduced temperature comparatively to where the engine is actually running.

I have seen this happen when I tagged an alligator snapping turtle on the highway with a lowered Prelude (not good for the car, but downright explosive for the turtle). It busted the radiator and as the temp began to climb, it suddenly dropped to show the needle below cold. That's when I knew that I could putt it along no further (I was just trying to limp it back into town), and would have to settle for finding a tow in the morning.

I cannot tell by your temp readings with your infrared thermometer whether or not this is your case, but just be sure to have your coolant topped off and see if you can witness any flow through the radiator after being certain that you are filled up on fluid. After that, replace the thermostat. Easy job.

Wow, that's really random and unfortunate.

So basically, this is what you want to check.

1. Coolant level. Fill up your reservoir to the recommended level. Then top off your radiator.

2. If that doesn't fix it, you can pull out your thermostat. It's fairly easy to get to, it's located right behind your lower radiator hose on the engine block. Be sure to pick up a new gasket either way. Drop it in a pot of water. Turn on the heat and you should see it open before the water boils. If not your thermostat is bad.

3. If that's not it, then you have a blockage somewhere, most likely in your radiator by the looks of your temperature readings. Or your water pump is completely shot.

 

[reelamin]

Thanks for the input from all. Hoping to cover all options or known things with this motor before I start the trial and "not fixed" route.

Gauge while going down highway reads in the bottom 25% and while idling in shop will climb to bottom 33%

Radiator is/was fully topped off with very clean radiator fluid.

After letting cool then starting and idling to monitor heat build up water pressure from heat pushed maybe a table spoon or so out of open radiator cap.

If the water pump was not working in my experience (all water cooled motors from single cylinder bikes to 500hp Cat Diesels) a engine will actually overheat very quickly. I have never had a water pump not work and cause the engine to run cold. LOL...there is a first time for everything and as I said asking for help.

This is why I took readings off the engine itself and they were matching the coolant. Oil pan read 150f.

I have to order a few other parts so I'll be ordering a thermostat and gasket it looks like to be prepared for the "is this it?....nope...this?....nope....next!!"

 

[reelamin]

Looks like a motor is a motor in regards to cooling systems. Closed the top hose off and was able to get the temp to rise some. Started pinching off the lower hose a little at a time. Temp rose even more so no question what the problem was. 20 minutes a new thermostat and problem solved.