Got my own now.

J

Jay Maynard

Hi all, bought a '75 M-M Landau Traditional for $1,000 yesterday. 68,000 miles, black, in really decent shape. Runs great except it overheats. Thought it might be the thermostat, took it out, still does it. I've already been told that the water pump may be a cause, not sure yet.
I'd like info on what quirks those 500 motors have, and if anything needs to be given specific attention as a known problem area.
I've run into 2 M-Ms that the speedometer doesn't work and the #2 DS door won't open. Mine follows that pattern.
Thanks for any and all advice and info.
 
RE OVERHEATING: Look inside the radiator (remove cap) if it looks like chocolate milk chances are radiator is plugged. Will need to go to radiator shop for cleaning. If coolant looks clean and clear check radiator at front for debris plugging air flow EG sticks leaves bugs etc. Last guess is timing retarded this will cause overheating symptom lazy slow revving.I have never had a problem with 500s overheating. My best thought is plugged radiator. Sounds like a great buy good luck with it.
 
like Peter said unless the belts are so loose they are not spinning the water pump over it's most likely the radiator. worse case senearo is a cracked head of leaking gasket. but not common on them.

the doors are always a lack of use problem. either the dirt builds up in them and the lock gets jammed half way or they rust from lack of grease and won't pop the latch. normal it's the back and left center doors that are the worse. getting them back open is a play with it kind of thing and my be easy or long winded.

most of the problems with one of these cars is sitting lack of use problems.

welcome to the joy of a old pro car. you fineness things you can get them all back working by cleaning mostly
 
Congratulations Jay! It sounds like you got a great deal, too!

There has been some really good advice posted here, regarding your overheating situation. I will just throw in a little experience that I have had with these Cadillacs of the vintage. There used to be a clutch-fan on these Seventies Cadillacs and I am not sure if you have one. But, if you do have one, you might consider replacing it. Apparently, when the clutch-fan goes bad, your fan still spins, but not fast enough, especially while driving. But, this may not apply to your car, it is just something I experienced multiple times.

Whatever you do, don't panic, you will get the problem resolved and then you will enjoy your new hearse.
 
Jay,
Congratulations.The 1975 and 1976 Cadillacs are great looking bodies. I will look forward to photos of your new adoption. After eliminating the other suspected problems, don't forget about the sending unit.
 
now that would be a guess. on the sending unit. I would try stock caddy if it was mine but I have heard some conflicting stuff on them.
 
Jay, the sending unit sends the temperature reading to the guage or warning light. I am not sure where it is located on your car because I am not mechanically inclined. I just know a lot from paying for repairs!! If the radiator and fan check out as suggested by the other posts, take a digital laser thermometer and measure the temperature on the two hoses going to and from the radiator. One hose should run approximately 30 degrees hotter than the other. If you find out the temperatures are below 200 degrees it is probably the guage or the sending unit. I don"t know if your state still has safety inspections but if they do and if they check headlight alignment the 1975 and 1976 were famous for the adjusting brackets breaking (I think they were plastic). I believe there are aftermarket replacements and McVey's may stock or know where you can buy some.
 
Thanks Phillip, when I first saw sending unit I thought about something fuel related. This car has no temp gauge on it, only an idiot light that comes on when it's too late.
 
true the Gage might be not reading right but it that were the case it would only read one thing all the time. then of course there would not be the hot runny green stuff coming out. which to me is running hot. if the gage is reading high that not running hot.

the check with the no contact thermometer would be in order. to confirm it now with a 190 deg thermostatic when it up to operating temperature the base of the housing should be right at 190 degrees and as stated the lower radiator hose will be a much lower temp reading. when you said running hot, I imagined boiling over. not just a Gage reading high. gauges work by grounding threw a resistance. the less resistance, the higher the reading.
 
Here are the pictures.
 

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Jay Maynard said:
Hi all, bought a '75 M-M Landau Traditional for $1,000 yesterday. 68,000 miles, black, in really decent shape. Runs great except it overheats. Thought it might be the thermostat, took it out, still does it. I've already been told that the water pump may be a cause, not sure yet.
I'd like info on what quirks those 500 motors have, and if anything needs to be given specific attention as a known problem area.
I've run into 2 M-Ms that the speedometer doesn't work and the #2 DS door won't open. Mine follows that pattern.
Thanks for any and all advice and info.
Click to expand...

You'll get it figured out in due time. My Lifeliner was beginning to overheat when I first got her. Did the hose thing, water pump, thermostat, tried them all. Had good water flow but turns out about have the radiator was clogged so it would not allow enough water to flow to keep the engine cool. New radiator solved all that.

Let us know.
 
If your radiator is in good shape, with no signs of leakage or external corrosion, there shouldn't be any reason to replace it. As Pete said, remove it, take it to a radiator shop and have them "boil it" to clean out the internal blockages. Before doing that, you can try flushing the cooling system yourself - any auto parts store will sell a quart size bottle of cooling system flush, you drain the antifreeze, fill the system with water, add the flush, run the car for in the driveway for a while, let it cool, drain the flush, run water through it again to rinse it out, and refill with fresh antifreeze - this also cleans the inside of the engine block, in addition to the radiator (As always, follow the directions on the bottle, dispose of all waste properly, etc. etc.,) If the car is really plugged up, the diy version may not be strong enough to get it done, but I would try that first. Not knowing your mechanical inclination, if you don't want to do that yourself, most any decent car shop should be able to do the same.

Good luck, and beautiful car, by the way.
- Jacob
 
This is the inside of the radiator of one of my '76s - if you drain your antifreeze down, and it looks like this (or worse) - the system definitely needs flushing. All that gunk prevents coolant flow through the system, and also acts as an insulator, retaining heat.
 

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Thanks Jacob. If I do go ahead and get a new radiatior, O'Reilly has them for $179.99 and can get it in the same day if you order it early enough.
 
Sorry Jay, I did not understand it was boiling over until your recent post. That is a fine looking coach. The black center on the wheel covers really give it a formal look. Good luck on your new radiator. I'm headed to O'Reily's now for a new battery for the 49.
 
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