1986 MGM, On thermometers and heating issues.

[Lothae]

I recently bought a 1986 MGM from a nice old guy that moved to NY from Florida and brought his behemoth. It is in excellent condition and has never seen a winter. The problem I am having though, is with the heat of my engine after running for a while.

I am pretty sure that my engine is running too hot after warming up. When I changed the spark plugs the other day I noticed that the ends were melted and were white, usually a sign from running too hot. The guy I bought it from had just replaced the radiator before I purchased it.

The problem I have is knowing whether the plugs were melted before or after the replacement of the radiator. I notice after running the engine a while it seems to get warm, but the indicator light doesn't come on, and it still runs relatively well.

The radiator coolant level has been consistantly full whenever I check it so I am ruling out the radiator as the problem. I think it might be the thermometer.... I notice that I am getting no heat from the vents inside the car whenever I turn them on, no matter how long the car is running. This leads me to believe I have a faulty thermometer.

I was wondering what your guys opinions are on this situation. I think I can get the thermometer relativly cheap, but I am not sure about the installation. I looked under the hood yesterday and I think I found it. I think its between the fan cowl/fan and the engine above the water pump. If I am correct there are two tubes going to it, and two or three bolts holding it on. I was wondering if anyone knew if this was the piece, and the difficulty of changing it. I'm pretty sure i can access it without taking off the fan/cowl, but I don't know if I have to drain the radiator fully before disconecting the hoses.



Any help would be appreciated.

[fredjacksonsan]

When you're saying thermometer, I'm thinking you mean thermostat? It's on the top of the block near the water pump. You might not have to drain the entire system to get at it. But thinking that this old guy may not have maintained the car that well, you'll likely want to flush the system and replace the coolant. Also, check inside the radiator to make sure that it is indeed new and not crusted over with age.

Your local auto parts store should be able to sell you the correct thermostat; and you should be able to locate it easily with their help.

[fredjacksonsan]

Also sounds like there has not been much maintenance by this nice old guy. With no heat, you may have a clogged heater core; you'll see two hoses coming back from the water pump area to the firewall; they're hooked to the heater core.

Sounds like this MGM needs a bit of TLC.....

[Lothae]

Yeah, whoops meant the thermostat. The radiator is new, about 2 months old according to the receipt and just by looking at it. He kept the car in good condition though, I bought it and it came with all the receipts for maintenance over the 18 years.


About the heater core being clogged, once I locate the hoses, is there a way to tell if it is clogged? Also if so is there a way to remidy this without swapping the whole core, I heard its one hell of a job.



Back to the thermostat though, I think it should be easy, the coolant is relatively new though, so I am not sure if I feel like buying a bunch more since it was just recently changed. I guess I could, the tap for it is on the bottom left of the radiator when facing the car right??



Also I am going to go take a few pics of the car if I find some batteries for my camera, so hopefully I can post them and maybe you could point out where the heater core hoses are.

[fredjacksonsan]

Check for clog....unhook the two heater hoses, and get your garden hose out. Hook it up to the inlet on the heater core and turn the water on. You should be able to see how much is flowing out; compare vs how much comes out of the hose. It may be completely clogged, or you may be able to use one of the flush kits for it; no guarantee, just might need to replace it.

Heater hoses easy to spot, they run on the passenger side of the engine, usually together, and terminate at the firewall.

If the coolant's new, then yeah just save it.

Thermostat is an easy replace job. The heater core is a tough one usually...

[Lothae]

Alright thanks, the info has been great but I have a few more questions:


As for the thermostat I took some pictures, I circled where the visible bolts are, but is there a third one underneath the hoses where I circled and put a question mark? If so, is it easy to get at? Also on the picture, the gasket looks like it is deteriorating rapidly. Does the thermostat I buy at a store come with a new gasket to put there or is that going to be extra?

Picture:
http://usera.imagecave.com/lothae/1.jpg


Also here is a pic of the radiator, I'm very sure its new:

http://usera.imagecave.com/lothae/2.jpg

And one last shot of my baby:

http://usera.imagecave.com/lothae/4.jpg


I still have a few things that I need to do to the beast to get her to my standards. Some of them are easy things like glueing a broken piece of plastic or such (the auto door lock buttons are horrible on this car, whoever designed them should be shot, hanged, then quartered.)

A larger one is removing a sucky tint job to the driver side rear window. I don't know why the guy put it on, or why he only put it on that side, but it looks tacky. Do the kits at Wal-Mart actually work for this job or are there better methods.

The last deals with my rear differential. It keeps roaring after I hit 5-10 mphs. I talked it over with a mechanic friend and he thinks that a pin is rubbing inside it and I would be better replacing the whole rear diff. I could do this but it would cost about 600 bucks (which I don't have.) I talked to another mechanic though and he said that it was prob the gasket had gone bad and it was rubbing. Any advice?

[fredjacksonsan]

Pic 1, the large hose exiting the lower left is the return to the radiator, and the long bolt at the end @ the engine is for the clamp. You'll need to remove the clamp, pull the hose off and then should see the thermostat/neck/housing just below. Can't see in the picture the 3rd bolt you're talking about. The new thermo should have a gasket with it, if not ask the parts guy for one.

Don't know anything about tinting.

Roaring? Is it a rumble or grinding or whining? Mine whined at 50mph. Sounds bad, you may want to pony up the 600, you could get a better set of gears and maybe a limited slip. Alternative: junkyard for a new axle or differential. Grinding bad, will have to open it up to have a look.

[Lothae]

Yeah, I am not sure about the rear diff. Hopefully its like a bad gasket, cause cash isn't always around for me. I have a weird feeling it will be something expensive though. The 600 is for a replacement part and installation, are there better aftermarkets with limited slip/better gears for around the same price?

[fredjacksonsan]

$600 isn't a bad price for where I live; I was quoted around $1000. Shop around a bit though (of course) $600 sounds high, but if they do the work right you should never have to worry about the rear end again. Doubt it's just a gasket. You could look for aftermarket sets of gears, but the big cost is the labor to put them in. Gears go for around $250 or so, the rest is labor/fluid/gaskets/etc. Put it this way though: if your rear end quits, so does your car.

[fredjacksonsan]

By the way, your MGM looks fantastic; mine looks like it was chewed up and spat out. Yours looks like it's worth putting the money into.

[Lothae]

Thanks for all the help. I guess I will prob go ahead and stick on a new rear end. Its a wise investment though, because the car overall is in good shape. I have bad luck when it comes to new cars so I decided this creme puff was worth it. It seems the newer the car is for me, the quicker it dies. They don't make them like they usto.


Thanks again.

[fredjacksonsan]

They sure don't. Hopefully that's changed, I just bought an 04 Dodge pickup.

[6502dude]

Originally Posted by fredjacksonsan

Check for clog....unhook the two heater hoses, and get your garden hose out. Hook it up to the inlet on the heater core and turn the water on. You should be able to see how much is flowing out; compare vs how much comes out of the hose. It may be completely clogged, or you may be able to use one of the flush kits for it; no guarantee, just might need to replace it.

Heater hoses easy to spot, they run on the passenger side of the engine, usually together, and terminate at the firewall.

If the coolant's new, then yeah just save it.

Thermostat is an easy replace job. The heater core is a tough one usually...

If all above is okay and heater core hoses are both hot when car is warmed up - check vacuum supply to vacuum motors which operate door flaps in plemum. You may have a broken vacuum supply tube or a bad vaccum motor that is preventing flapper door from allowing heat from heater core fully into air distribution plenum. Defoster heat to windshield will still work (poorly) and you will have no heat from vent or floor if you have a vacuum or vaccum motor problem.

[fredjacksonsan]

Thanks dude, I'm a little weak with underdash stuff.

[Lothae]

I am assuming these can be accessed from underneath the drivers side dash?