Engine Redlining HELP

I have a 2001 Tacoma TRD and the temperature gauge was running hot so I sent it to my mechanic. He replaced thermostat and refilled coolant (as well as replacing drive belts) but on my drive home my truck redlined... It didn't even redline before the mechanic, but before the temp gauge would go from about 1/2 gauge to 3/4 gauge, never redline. Could it be an improper/bad thermostat that was put in? Or maybe a bad head gasket? It has also been very hot out recently. I really dont know how common head gasket issues even are on the tacos. Anyone have any suggestions? I dont want to blow a thousand dollars on a head gasket if it's fine.

 

Get a Scan Guage II and plug it in to the OBD2 port. You can now get a true temp reading.

It's a fact that the temp gauges on any Toyota are very vague at best. Do not trust them.

If the truck actually was hotter after you got it back, I'm betting you have an air pocket in your cooling system.

Squeezing the radiator hoses with the cap off can help push the air bubble out.

Do this after the truck cools down. Do not open the cap on a hot engine. You can burn yourself with escaping coolant that is under pressure.

 

Overheating could be caused by the radiator. May be on its way out.

 

Cooling system mot properly " Burped" , air bled out of the cooling system . You now have an air pocket that needs to be dealt with

 

I don't know if I've ever seen a plugged radiator on a Tacoma. Usually they develope stress cracks near the tank seams.

I consider rads a consumable part. Change them every 150,000 miles or 10 years.

A coolant/rad flush is $125. A new rad is $80.

A new rad and new coolant for less than $100? Sign me up.

 

I second that. There are two issues with temperature gauge:
1. The sender is located at the top hose going to radiator. It is not the same as the engine temperature that is measured by the ECU reporting sensor located close to the block
2. The sender can malfunction for unknown reason (probably age). Two years ago the gauge started to show temperature lower than it should be driving me nuts. After replacing the sender for a brand new one everything went back to normal.

The best point to measure the engine temperature (assuming you are not missing coolant) is by reading the ECT value directly from the ECU (using Scan Gauge for example).

 

I agree with U S Marine. Steam is hotter than water which will cause a spike in temp if a air pocket is in the cooling system. Once all the air has worked its way out, everything should return to normal. If the spike DIDN'T go down then you have a circulation problem that could be caused by a plugged radiator, head gasket leak, low coolant, faulty thermostat and or water pump.

 

Ill try and release any air in the coolant if any. Also if I use the Scan Gauge and it reads the same as my dash gauge then should I just assume its the radiator/head gasket?

 

Don't assume that.

A leakdown test will need to be done 1st. No sense getting worked up yet.

Start simple then move to expensive.

Which engine do you have. Both are pretty rugged and can stand running warm for short durations.

 

I have the 3.4L V6 with 166,XXX miles on it. I might end up sending it back to mechanic and see what happens too, Im sure he bled coolant and all so that may not be the problem. The engine doesnt just continuoisly increse to redline, itll stay at normal temp for a while then rise up later into drive. My mechanic drove it before I even got it then it started to rise just as I got home (20min drive).

 

Head gasket won't cause over heating. Not until all the coolant has either leaked outward running down the block or leaked inward into the piston.
If there's no steam coming out of the exhaust and the oil is not grey/white and foamy, head is fine. Look elsewhere.
How's the fan clutch. If it had a clutch then?

 

fan is 100% good, I just ran it at idle for a bit in the driveway and the dash gauge fluttered its way up in a weird way. maybe it was really a bad thermostat. but I did hear some tsss sounds coming from the engine...dont know what that is.

 

Testing fan clutch is easy ....


Check for oil accumulation on the part of the fan clutch where the spring or valve is located . If oil is present clutch is worn and needs replacement

With engine completely cold ( sitting overnight) attempt to spin the fan . If it turns more than 5 times it worn out

With engine warm fan should turn but resistance felt

 

Did the mechanic install the thermostat in the correct position?
6 o’clock or 12 o’clock?

 

well he installed a stant 14078 thermostat that apparently sounds like it has no tab to mark the position.

 

Jigger valve has to be in the 6 o’clock position or it will run 8-15 degrees hotter

 

when i open my radiator cap and let my truck idle should i be able to see coolant flowing? cause when i let it idle i saw no coolant through radiator, would that mean my radiator is leaking.

 

The coolant sensor for the computer and the coolant sensor for the dash are separate so your engine computer is not seeing the same thing as your dash. A scangauge or Bluetooth obd2 scanner with live data scanning capabilities will tell you what your computer is seeing, not what your dash is reporting.

I’d add coolant until you can see it and then check it the next day or two.

Check out the foseal WiFi OBD2 dongle.

 

You won't see coolant flowing.

 

They need to be weary of the head gasket as well. Or even a cracked cylinder.. Don't rule anything out check out everything...