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Discussion Starter #1 (Edited)
hi,

i have the following issue.

if i start the car and switch heat on then heat gauge goes up to max and the warning light and sound come on for about 10 seconds then the gauge drops back down to normal just below the middle mark. eventually the warm air will start coming out as long as i'm driving if i stop and idle it goes cold again until i start driving again

if i dont switch the heat on when i start the car then the heat gauge will gradually go till the middle mark and if i then switch the heat on then the gauge stays at the normal position but the heat still goes cold when i stop at a red light or if just idling when parked.

i checked coolant level and that was full.

any ideas or advice would be very helpful and appreciated

thanks
 

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Did you open the radiator cap or just check the plastic reservoir?
 

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Why are you letting this car overheat? Is it a throw away car?

Ask around, find a good shop, and take it there, and get them to look at it before you do real damage. Most cooling system issues aren't that expensive.

That said, your problem could be solved by something as simple as bleeding the cooling system.
 

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Sounded like low coolant to me too but you checked that.

My guess is a weak water pump, the impeller may be worn or spinning on the shaft, and not circulating coolant for the heater system at idle.

How's the tension on your serpentine belt?
 

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Is your heater blower working? Might you only be getting heat when the van is moving because that's the only way the air is blowing through the heater?

What Jeepman said about the water pump being weak could happen, but is rare. A slipping belt is something to check.

<<...if i start the car and switch heat on then heat gauge goes up to max and the warning light and sound come on for about 10 seconds then the gauge drops back down to normal just below the middle mark.>>

Do you mean this happens as soon as you start the van when it's cold? If so, you probably have an electrical problem. If it is happening over a period of 10-15 minutes then your thermostat may be sticking.

At any time have you dumped a bunch of Stop-Leak in the radiator? That stuff can clog things up and cause trouble.

Bill
 

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Discussion Starter #8 (Edited)
ok, the heater blower is working fine

it happens over about ten minutes, not immediately. as i explained the heat gauge goes to maximum and beeps only if i switch the heat on when the engine is still cold and it is then blowing cold air until engine heats up which is when the gauge goes to maximum for about ten seconds then drops rapidly back to the normal position.

if i dont switch heat on when i start the car it never goes to maximum it just gradually goes to the normal position after about ten minutes of driving and stays there.

also, if i wait and only switch heating on after engine has heated up then the gauge does not go to maximum and stays at the normal position! but i still have the issue of the heat going cold when idling!

that is why i dont think it is a coolant issue but a heating issue.

no "stop leak" has ever been used.

i agree that it could indicate a sticking thermostat. where can i find instructions for changing thermostat?

i thank you all for your insightful, helpful and informative replies so far!
 

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The coolant is circulated through the heater lines regardless of whether your heat is on or off. In "the old days", there was a control valve on the heater line, not so for the 3rd Generation onward. The constant flow keeps the heater lines from plugging up over the summer.

Gauge going to maximum and then settling down to normal indicates a stuck thermostat or faulty gauge. I can't see how turning your heat on has anything to do with that.

No heat at idle indicates lack of flow through the heater pipes.

At idle, is the air conditioning coming on maybe? If so, check your ambient temperature sensor located in back of your front fascia (grill and near the middle I think) to see if it is loose from its bracket and lying against the radiator. This can cause the system to read a "hot" ambient temperature and automatically activate the air conditioning. Maybe it also activates a "hot" condition initially via the light/sound if you are calling for heat (just guessing on that).

Do you have automatic temperature control or a manual system?
 

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Discussion Starter #10
it is a manual system as far as i know.

i will check the temperature sensor as you suggested.

thanks again.
 

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Probably at this point it wouldn't hurt anything to change the thermostat. It's not a real hard job (usually). Take the upper radiator hose off the thermostat housing/water outlet first, with a drain pan underneath to catch the coolant. Then take the two bolts out of the water outlet and pull it off. The tricky part is getting the thermostat out as they stake the metal over the edge at the factory. A Dremel works well to 'un-stake' it. Clean the gasket surfaces real well, hold the new T-stat in place with some gasket adhesive and bolt things back together with a new gasket. I bought a new T-stat recently and with the premium silicone gasket it was $27 from NAPA, which I thought was pretty high but the gasket was expensive.

Bill
 
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