'89 SHO First Overheated, then Leaking Coolant - Happy Ending?

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DeepPower

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Driving home Friday night, I pulled into a shopping mall and stopped the SHO. I immediately saw/smelled coolant steam coming from under the hood. I opened the hood and saw steam coming from the thermostat housing. I tuned the key to the On position and saw the temp gauge rise to the N in Normal.

This changed my shopping plans. With the hood closed but not locked, I walked to the hardware store and bought two gallons of coolant, then the supermarket and bought two gallons of distilled water.

Half an hour later I drove the final 1/2 mile home although for some reason I had a **** of a time getting the car to start. Temp gauge reached the "N" for the two-minute drive, I coasted most of the way with the car in neutral.

Popped the hood and let the car cool in my garage overnight. I figured the thermostat failed shut (it's a "Fail-Safe" brand I had installed 10K miles ago) so Saturday I took a walk to O'Reillys and bought a new Murray #3978 180°F thermostat.

Removed the Fail-Safe - it is now stuck open. Don't know if that means the thermostat failed closed, then when it cooled it opened again? Thermostat is clean, no gunk, a little blackened at the top housing on the side of the jiggle valve.

Installed the new thermostat. The car took just a little under two gallons of antifreeze and water. Car started right up and running beautifully, but looked underneath and coolant was leaking from somewhere - it was dripping from near the oil pan. Checked the thermostat housing and it's secure. Looked and couldn't find a leak anywhere. I'm thinking ga$ket or water$pump.

Okay, at this point in writing this post I started the car one last time to see if I could find the leak. There's a short hose from the throttle body housing to the engine (what's it called?), the hose is soft and mushy and terribly ripped at the clamp at the engine side. I'm gonna walk to O'Reilly's again and replace that hose. BTW I've had a slight coolant leak for the past few months that I now know the source of. Thank you for listening and Happy Easter!
 
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SHOdded

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One of the TB hoses on my SHO had spring a pinhole leak, enough to smell a bit but not be visible without close inspection. So I hope that is indeed your culprit, and of course, replace all those TB hoses while you are trying the fix. Good luck, and Happy Easter!
 

DeepPower

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Okay, so the hose is for the throttle body coolant bypass. It heats up the throttle body to keep the throttle plate from sticking in cold weather. But this also heats the incoming air. Think I'm gonna bypass it.
 

DeepPower

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O'Reilly's didn't have coolant hoses in that size, only fuel hoses. And while the car didn't overheat, I still got some steam, but this time I think it's from the thermostat housing because I stripped the top nut on it.

I'm gonna fill the radiator to the top tomorrow take the 10min drive to my mechanic near where I work, watching the temp gauge and praying all the way.
 

Irish Pride

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Your best option is to pull the intake and replace all the heater hoses at once. Bypass the TB like you said but get all the others. Especially the ones running to the heater core. Oreillys does carry those hoses. I think the one you need is #18010. Once you replace one hose the next one down the line will only last so long.
 

DeepPower

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Your best option is to pull the intake and replace all the heater hoses at once. Bypass the TB like you said but get all the others. Especially the ones running to the heater core. Oreillys does carry those hoses. I think the one you need is #18010. Once you replace one hose the next one down the line will only last so long.
Okay, so basically I should tell my mechanic to replace any coolant hose that isn't 100%. Sounds like a plan.
Oddly enough O'Reilly's didn't have any coolant hoses at all for my car. They couldn't even find a 10mm nut for me to replace the one I stripped on the thermostat housing. Although on Easter Sunday I can tell you that the guys behind the counter were definitely not First Team.
 

Irish Pride

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I'll get you s list of the part numbers to ask for tomorrow. If your Oreillys doesn't have the hoses they will be able to get them in a matter of hours if you tell them what to get. My store keeps them in stock.
 

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