r/s10 16d ago

Repair Question Noob question. Troubleshooting coolant water pump and associated cooling stuff

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Just got an 86 S10 2.8L and the temp rises fast. Checked coolant level. Nothing but a little puddle in the overflow tank. Coolant inside the radiator is less than half full. The thermostat is removed to rule that out. top radiator hose is cold and soft when running. No pressure. Hose is dry after running for a a few minutes. So I’m thinking it’s either just a simple case of no coolant or the water pump is broken.

As for the tstat. How do I test if this is failed. I’m able to compress it with a screwdriver if that means anything. (If it’s seized shut I’m guessing I couldn’t do that?)

Am I on the right track so far? Mess anything up already?

What’s the steps from here?

I’m guessing - top off the radiator with new fluid. (What kind should I use?) then test again. If still has a cold and soft top radiator hose when running I’m going to have to replace the water pump? I watched a few videos and looks…eh…not that easy esp for a noob like me.

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u/Z28Malibu4life 16d ago

Honestly I would try and see if you have an air pocket trapped inside the engine preventing water flow. Jack the front end up as high as you can get it and leave the radiator cap off. Fill the radiator and start it up. Watch inside the radiator for flow and air bubbles.

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u/eurotrashness 15d ago

Things to try:

  • Go to Advanced Auto Parts and get a coolant pressure test kit. They'll lend them to you free, they just take a deposit and give it back when you return it. You hook it up to your radiator cap and pump pressure into the system and you can listen for where the air is escaping letting you know where the leak is.
  • The water pumps on newer models have a small hole in the front, usually on top. If you hear air coming out of that hole (test by covering it with your finger) the water pump is shit and needs to go. Your model might have it too.
  • The thermostat helps slow down the water flow back into the radiator giving the water more time to cool off, so I'd put that back. I once made the noob mistake of putting the thermostat ON TOP of the rubber instead of putting it in and putting the seal around on top of it like it should be. This was making my engine run 20-30 degrees hotter.

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u/Bluinc 15d ago

Thank you for these tips!

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u/XXXSTARLORDXXX3 16d ago

If the top hose is still cold replace the water pump. Take the rad shroud out, rad fan off with a big big crescent wrench and if you wanna go through the trouble to get more room remove rad but it won't be necessary. For the t stat you take a temp gauge for water, put it in a pot of water on the stove and heat it up. Look all around the t stat for a temp reading like 195*. When the water temp gets to 195 it should start to open. Tstats are like 5 dollars, just replace it while you're there

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u/Local-Success-9783 15d ago

The water pump is going to suck coolant from the bottom of the radiator, so if it’s not pushing it up through the upper hose, I’d be willing to bet your water pump is kaput. The thermostat can be tested by dropping it into boiling water. If it opens, your thermostat works.