I need help with my Mercury Grand Marquis

[bomelia]

Look, the tires are worth more than the car. So a $500 repair bill is out of the question (I hope).

I have NO heat in my car. Once, I changed the thermostat and that helped. Then the heat went out again. So I changed the thermostat again. This time no luck. Is it possible that the heater core is plugged?

Mike

[4RE KLR]

Mike
It is very possible the core is stopped up.

You can take the top hose running to it and start the car. If you have circulation coming out of the hose turn the car back off.

Take off the bottom hose and hook up a garden hose to the top inlet and turn it on. It may take a second or so but that will wash out the core if it it stopped up. The garden hose usually has more pressure than the water pump does.

My father in laws truck had the same problem and we did this very same thing this weekend. The heater works great now. There was just no circulation getting into the core itself.

It was stopped up with all kinds of crap from over the years. The little Ford Ranger truck has almost 500K miles on it and still going.

[bomelia]

So you are talking about flushing the whole system... correct? Perhaps put some of that flush stuff in it first?

Mike

[4RE KLR]

Originally Posted by bomelia

So you are talking about flushing the whole system... correct? Perhaps put some of that flush stuff in it first?

Mike

Well flushing the whole system is rarely a bad idea.
But I would just flush the core first and see if that is the problem.

You will be surprised what all comes out of it with just water.

Preston makes a descent flush kit but I would just use water first. If the system flows freely you know you have a different problem.

Ford's have 'doors' in the heater core boxes that open and close when you turn on the heater. The door could be stuck closed, thus not letting the heat get to the interior. I would bet the problem is in the core though. Either way it should be a simple and inexpensive fix. If the core was leaking it is a big pain in the ass to get to.

Flush the core first, it is quick and easy.

[Wayne Maybury]

You said that you changed the thermostat. Are you sure that you got all of the air out afterwards? An air lock will result in no heat. Remove the rad cap and make sure that the system is full before doing anything else.

Wayne

[VRM]

Get some radiator cleaner or CLR and set up a closed system consisting of the heater core, and the hoses disconnected from the block. You may want to get some longer hoses (I have a couple of 5 footers that I use) and some clamps and some plastic or nylon spigots.
Drain the coolant from the core, and then fill with the cleaner following the directions (I prefer a stronger mix of cleaner). Let it sit for a half hour or so, and then drain into a bucket - this stuff is a mild acid, so be careful with it. Then use your garden hose to blow out the loosened gunk - keep forcing water through until it comes out clear.

I've been told that Ford products have their cores buried in the dash - my old Blazer had it behind a panel in the firewall - really easy to get to. They are easy to replace if it does not clean out properly, but you may have to take apart the entire dash assembly.

You guys need heaters in Alabama?!?

Steve

[bomelia]

Originally Posted by VRM

Get some radiator cleaner or CLR and set up a closed system consisting of the heater core, and the hoses disconnected from the block. You may want to get some longer hoses (I have a couple of 5 footers that I use) and some clamps and some plastic or nylon spigots.
Drain the coolant from the core, and then fill with the cleaner following the directions (I prefer a stronger mix of cleaner). Let it sit for a half hour or so, and then drain into a bucket - this stuff is a mild acid, so be careful with it. Then use your garden hose to blow out the loosened gunk - keep forcing water through until it comes out clear.

I've been told that Ford products have their cores buried in the dash - my old Blazer had it behind a panel in the firewall - really easy to get to. They are easy to replace if it does not clean out properly, but you may have to take apart the entire dash assembly.

You guys need heaters in Alabama?!?

Steve

Thanks Steve, but yes we do. There are times when our beagle pelts are not enough to keep us warm enough.

[VRM]

Originally Posted by bomelia

Thanks Steve, but yes we do. There are times when our beagle pelts are not enough to keep us warm enough.

Well maybe if you hadn't turned it into a convertible with a sawsall you wouldn't have this problem...

If you have never flushed the system it might not be a bad idea to do the radiator as well.

[392cobra]

Originally Posted by bomelia

Thanks Steve, but yes we do. There are times when our beagle pelts are not enough to keep us warm enough.

One other tip... After you get it going again and before you slide it into gear....be sure to get the tires & wheels back off your home and back onto your ride.

[VRM]

Originally Posted by 392cobra

One other tip... After you get it going again and before you slide it into gear....be sure to get the tires & wheels back off your home and back onto your ride.

Hah!! I almost ruined a keyboard reading this one!

[392cobra]

You have to be sure you actually have the ability to flow water thru the core.Could be the valve controling the water flow thru the core isn't opening.
Some are vaccum,elect. or mechanical.

[427 S/O]

Mike, check the vacuum hoses under the dash, if you can see them. I knocked off a vacuum hose once and it only blew cold air until I found the problem. Also check the cool-hot control, I believe it opens a flapper for air flow.

[427 S/O]

This 'may' help.......



http://www.justanswer.com/view_image...807_wiring.jpg

[nevermind65]

This sounds a bit odd. You said you replaced the thermostat and that helped, but then the heat stopped working AGAIN? What do you mean by "it helped"? Did it give good heat with the new thermostat, or did it just barely warm the car?

I'd check the stuff everybody else above wrote, but it sounds like you might have another bad thermostat.