Am wondering if anyone has the disassembly instructions for and 86 with the tuned port injection. Need to replace the thermostat. Believe I could possibly get to it but there is a smog sensor that sits directly above one of the bolts that is broke and needs to be replaced also.

Take the TB off 1st

then the t-stat housing is easily reached.

But it's really a good idea to drain some coolant from the rad first... get it below the engine block.

use some hi-tack on the gasket.

Ok I give, what is the TB? If it's the chamber running down the center of the engine then yes if I get it off it will be easy to reach the thermostat housing but what are the steps?
Ok had to think about that, you probably mean the throttle body. There's five bolts on each side connecting the intake and then the throttle cables on the front. Anything else that I might need to know? It looks like you could leave the cables on and just lay it over to the side.

Quote:
Only 4 ( M10 ) bolts holding the TB on front of intake; they are all you have to undo
May have to disconnect the lower U shaped hose from intake manifold so you can lift TB clear of thermo housing
(Disregard hi lighted sensor , was for another question )


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This is a good time to do the throttle body coolant bypass. It eliminates the little coolant hose under the TB and makes it easier next time you take the TB off. That way, you don't have to drain any coolant. Cleans things up a bit.

Matthew

Thanks for the info. Got it all off but am wondering about the bypass? What do you have to do? Original problem as told to me was overheating, said the thermostat wasn't opening but the stat looks fine. Will replace but is there a certain temp that I should get? There's also a sensor that bolts to the thermostat housing with two connectors and two air hoses, both of which I found broke. Looks like one goes to the TB and the other to a plastic tube running under the intake manifold, know which one goes where? I also have a low coolant lite, where is the sensor for this?

what is your definition of overheating? was it boiling over? did the dash warning light come on?

these vettes run hotter than people are used to. The stat opens at 195, and the fan comes on at 228F. The secondary fan if you have it comes on at 238F.

I would consider any temp between 190-238F as normal. When you get the stat out test it in a pot on the stove with a thermometer in there to verify whether it was the culprit. And then replace it anyways. Stock 195 is fine, or 180F is fine. Don't go lower. A lower rated thermostat will not fix an overheating problem, nor will it lower the peak temps the car reaches.

If you have a low coolant light, that's probably your overheating problem. The cooling system needs to be full in order to build pressure. If it isn't under pressure, the boiling point is much lower, and it could possibly boil before even reaching the fan temp.

The bypass connects from the front nipple on the intake base to the upper heater hose hard line going into the fire wall. There's several ways to get it there, but the easy way is to route the hose over the valve cover.

The lines under the TB you are talking about sound like vacuum lines. One runs under the plenum toward the rear passenger side of the intake. The other runs out the drivers side of the engine. They connect to eachother and tee up into a vacuum port on the bottomside of the throttle body. Look for a sticker on your radiator shroud for the exact vacuum routing. There are subtle changes between years.

Postal - you are essentially removing a small loop from the system with the bypass. The coolant goes direct between the heater core and manifold as opposed to having to make another route through the TB.

As far as the low coolant light, you probably have air in your system. You need to "burp" it. With the car cold, start the car and use the radiator cap. With one hand, open the TB linkage to about 2000 rpms. This will suck coolant into the motor and you'll see it drop in the radiator. Add coolant until it's filled, then cap off. You might need to repeat once more. You can also jack the front p/s to help.

195* is stock, some put in 180*.

Plastic hoses are vacuum, lines. You can get replacement hose in a small spool at the parts store for about $4. Just cut to length, use a lighter to soften and bend it.

Matthew

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