Other heating problems

[peter59]

My son has an 89 Cherokee that won't generate any heat in the cab. We installed a new thermostat and still no heat. I've never seen one of these things before and installed the new part the way the old one came out. Is it possible the old one was in backwards and I just did the same thing? How do you tell? Shouldn't the spring be pointed into the engine block rather than into the hose? The hoses from the overflow get hot, but there's no coolant draw from it. The temp gauge is pegged, but it's pegged all the time anyway, even when the vehicle is off and stone cold, so I can't tell anything from that. The engine doesn't appear to be overheating, either. I boiled the old thermostat and it opens, then closes as it cools. Sounds right. 'Sup?

[Saudade]

The spring side goes into the engine block. Sounds like the old one is working OK.

Make sure the coolant level is full. "Closed" cooling systems, like on your 89 are notorious for trapping air in them and keep the engine from cooling properly (and can affect your heating). You can search the forum for "burping" the cooling system and get several methods for doing it.

If you're still not getting heat, you might have a problem with the heater valve (the gizmo on the hoses going the the heater core with a small vacuum line) or even a vacuum problem.

There is also a door that's controled by the temp lever on your dashboard that moves the door to allow air to flow through the heater core. If the door is "stuck" or disconnected from the lever, it will could allow the air to bypass the core and blow cold air.

The sending unit for the temp gauge is located on the rear, driver side of the cylinder head. There is a single wire coming off the top. Make sure it's connected and not shorting out.

If you haven't flushed the system in a while, your core could be plugged as well

I'd check the coolant level first and adjust as needed. Then move on to the other items. However, your gauge problem needs attention regardless.

[peter59]

Originally Posted by Saudade

The spring side goes into the engine block. Sounds like the old one is working OK.

Make sure the coolant level is full. "Closed" cooling systems, like on your 89 are notorious for trapping air in them and keep the engine from cooling properly (and can affect your heating). You can search the forum for "burping" the cooling system and get several methods for doing it.

If you're still not getting heat, you might have a problem with the heater valve (the gizmo on the hoses going the the heater core with a small vacuum line) or even a vacuum problem.

There is also a door that's controled by the temp lever on your dashboard that moves the door to allow air to flow through the heater core. If the door is "stuck" or disconnected from the lever, it will could allow the air to bypass the core and blow cold air.

The sending unit for the temp gauge is located on the rear, driver side of the cylinder head. There is a single wire coming off the top. Make sure it's connected and not shorting out.

If you haven't flushed the system in a while, your core could be plugged as well

I'd check the coolant level first and adjust as needed. Then move on to the other items. However, your gauge problem needs attention regardless.

Regarding the thermostat: I kind of thought it didn't look right. Regarding the rest: All good stuff to check out. I'll have to print this so I can remember it all. Thanks a million.