Rebuilt the original 472 over the Winter/Spring and have had it out on the road less than 1000 miles doing some fine tuning etc. She is running smoooooth and strong and have mostly had it out on nice cooler late Summer days. The last couple times I got home just after dark and noticed my "Water Temp" light every so slightly lit. I couldn't see it during the day it was so dim, but it's not on at start up in the garage so I'm not sure how long it's taking to come on.
Along with the complete rebuild I've:
*Double checked timing and its EXACTLY 5 degrees before TDC
*All cooling components were rebuilt or new (Water Pump, Fan Clutch, Radiator, Hoses, Heater Core...)
*New 180 Degree "Fail Safe" T-Stat
*New Cooling Temp Sender
It doesn't "Seem" hot and I wasn't idling around town in hot weather when it happened either. That light lit up brightly at break in when timing was off and she got a little hot. The plugs look a little bit lean, but she's running so good. I don't have a temp gauge currently, but man everything is new. Why would it light up just dimly - Anybody seen this before/have ideas?
Disclaimer: The one thing I know is wrong is that I haven't installed the small braided ground from the P/S Head to firewall as I couldn't locate/think the spade broke off. I know a bad ground can cause weird things with lights, but would think it has plenty of other grounds without this.
Thanks,
Might want to test your rad's pressure cap, or if no acess to a tester-just replace it. With a tester you could also pressure test the entire system and look for coolant leaks. Clay/Lexi
Sounds like you MIGHT have the wrong sensor. I assume we are talking about the sensor that sits in tec drone center under the AC compressor
Greg Surfas
Most likely its a bad or wrong sender but you want to be sure so pick yourself up one of those IR temp guns, they are cheap and easy to find these days and even the cheap ones seem to be reasonably accurate. With the gun you can verify that you are not actually hot enough that the light should be coming on.
If you have an AC compressor in place you won't likely be able to read the sender but its in the same passage that goes over by the base of the distributor so you should be able to get a good reading there.
Radiator Cap is new and not a drop of coolant leaking anywhere.
Yep it's the coolant temp sender under the AC Compressor. It's a "Standard Motor Products TS6" that Rock Auto listed as the replacement part.
My buddy has a temp gun so I'll try testing in that area next time I have it out.
Try putting another at least temporary ground on it and see what that does.
A SMP TS-6 is the sensor for the temperature gage. The sensor you need for the warning light is different. I will look tomorrow for the part number.
Greg Surfas
You did a ton of motor work and cooling system work--- use that laser thermometer (if it's a good one... most of the cheap ones are less than worthless junk). Install a temp gauge in your engine compartment. NEVER trust the idiot lights...(cautionary tale) on a hot sunny day on route 95 in Florida following a complete engine and cooling system rebuild, I couldn't see the idiot light "glowing"--- radiator blew out and engine head gasket failed. While taking out the blown radiator,we discovered a bunch of gunk blocking the radiator passages-- coolant couldn't pass through the radiator--- so consider a serious back flush and an installation of a cooling system filter.All good insurance for an old engine that could have a pile of accumulated muck in the engine's water jacket.
My understanding is the water temp sender is under the AC compressor is for the water temp light and the sensor at the left rear (D/S) of the block is the thermonuclear meltdown engine temp light. The engine was taken down to the bare block and flushed Etc so I'm confident everything is clean. Hopefully either insufficient ground or a bad sender. I did see a negative review on that sender about erroneous readings, I'll have to see if my service manual shows what the "Water Temp" on-temp should be. The extra ground is an easy first check so I'll try that next time.
Greg seems to have a list of the correct sending unit parts. He's already told you the one you replaced is for a gauge unit. PM/Email/Call if you know him well enough. He said he would post the correct part number tomorrow, yesterday and we still have 12 hours left, give or take.
It's too damned hot in Texas to be in a hurry right now.
You are aware I'm semi-joking here, right?
Finally found one of the new sensors I knew I had but were hiding from me. Here is the part number and a couple of pictures
By the way, the true function of this sensor/light system is "low coolant" indication. When the coolant drops below the level of the sensor, at say 220 degrees F which is within the normal range, steam at radiator cap pressure begins to form and becomes super-heated above the temperature of the water below it. When the temperature of the steam reaches 260 degrees F, the sensor trips and grounds the circuit lighting the light.
Greg Surfas
Quote from: Cadillac Kid on September 14, 2024, 12:41:56 AMA SMP TS-6 is the sensor for the temperature gage. The sensor you need for the warning light is different. I will look tomorrow for the part number.
Greg Surfas
Ok, NOW I understand what you're saying. I didn't realize there was a difference and when I ordered and thought "Heck the one that's .55 more must be the better one, I'll buy that" - I completely overlooked "With Gauge"
Serves me right for being a spendthrift. I'll get this changed out this week and report back. Thanks!!!
Quote from: "Cadillac Kid" Greg Surfas 15364 on September 14, 2024, 12:41:56 AMA SMP TS-6 is the sensor for the temperature gage. The sensor you need for the warning light is different. I will look tomorrow for the part number.
Greg Surfas
1969s do not have a temp gauge. The last year for the gauge was 1968. They had to make room in the dash for the left and right arrows, so away wen the temp gauge.
The 1969s and later had the coolant overflow recovery tank, making coolant loss a lot less of a problem.
In case anyone needs one the correct style coolant temperature switches are available through Cad Company (Part# WS21101). I replaced mine thinking I'd put the problem behind me, but noticed very faintly the temp light on during a night cruise (You definitely can't see it during the day). I still thought maybe it was just something funky with the dash light or grounds, but driving back from the lake a few weeks ago (about an hour at highway speeds) she ran flawlessly, then when I got off the highway at a light she just died and cranked extremely slow upon restart which I didn't think was going to happen. She then suddenly fired up but it worried me - once this heat wave dies down I will recheck the timing, but man she is running so smooth I just can't see it being timing...
Have you been able to verify what temps you are actually running? If you are running hot for some reason there are a few options for why it could stall and the slow cranking. But you could also have other issues that are not directly related that just happen to be happening at the same time.
I suspect that you ignored my post from last September. The accumulation of rust and gunk IN THE COOLING passages and engine's water jackets is a slow moving time bomb for your rebuilt engine. Over 5 decades, This material clogs radiator passages and well as the head gasket and causes the engine to overheat in critical areas.
Use a laser thermometer (if it's a good one... most of the cheap ones are less than worthless junk). Install a temp gauge in your engine compartment. NEVER trust the idiot lights...(cautionary tale) on a hot sunny day on route 95 in Florida following a complete engine and cooling system rebuild, I couldn't see the idiot light "glowing"--- radiator blew out and engine head gasket failed. While taking out the blown radiator,we discovered a bunch of gunk blocking the NEW radiator passages-- coolant couldn't pass through the radiator--- so consider a serious back flush and an installation of a cooling system filter.All good insurance for an old engine that could have a pile of accumulated muck in the engine's water jacket.
Good advice. I installed a mechanical temperature gage in my Cadillac, and wired it to my headlight switch so the dial is lit when the lights are turned on. I always want to know what is going on inside my engine when out on the road. Clay/Lexi
It's been unbearably hot and humid here for the last few weeks so no cruising lately. However, I changed the oil the other day, FINALLY found where my one small missing ground went, and did some other minor maintenance and then went for a cooler evening cruise and the Water Temp lit very dimly again - almost impossible to see at idle and gets a bit brighter when in the throttle. I don't have it in from of me but noticed that the service manual states that 3 lights are to illuminate at key on (GEN, OIL, and WATER TEMP). However my WATER TEMP is NOT illuminating at key on which is making me question that it's maybe a electrical issue? There is key on power at the coil + which is where the Coolant Temp Switch get's it's power so I'm not sure why it wouldn't light up. I purchased a quality laser thermometer and will take some readings this week for a sanity check and go from there.
For the record the engine was stripped to the bare block, hot tanked at reputable local machine shop, and ALL of the cooling related components are new (radiator was went through by a reputable local company), so I don't see how there could be any gunk in the cooling system. We also vacuum filled the cooling system. I'll get temps and report back, but if anyone has an idea based on the light not illuminating at key on please chime in. Thanks
So so far you have not actually tried to verify what temps your engine is running at? The first step in troubleshooting any sort of monitoring or alarm system is to make sure its not just doing its job.
In the 70's things got pretty complex mostly due to the fact that there was only one alarm buzzer in the car. I'm not sure what they had going on in 69 but as time went on the same buzzer for some of the lights also was tied to the key being in with the door open as well as the seat belts. Many people didn't like the key buzzer and would do maybe not the best thought out or implemented modifications to change that and then when it got into the seat belts things tended to get really crazy since people really didn't like seat belts.
These cars didn't just have a body control module programmed to figure out when to buzz the buzzer or turn the warning lights on. Like everything back in the olden days this stuff was so complex yet simple once you figure out how its supposed to work. They used all sorts of tricks and short cuts to keep things as simple as possible.
You need to (once you verify that its not just hot) get the diagram for a 69, find the light and see what all its connected to. My guess is there is gonna be more than just a single wire running out to the sensor on the engine and a direct link to a fuse on the other side. That lamp check circuit is gonna be in there as well as possibly a buzzer.
I'm curious. Where is the best place to aim an IR gun to take a temp reading? On my 41 there is a lot of exposed block to check. But in the newer ones with the valve covers and exhaust manifolds not so much.
When I'm checking against a gauge or light I will probe the area with the sender. Its not going to be the exact same as the coolant in the area but typically the area where the sender is isn't all that thick or close to some major heat source its gonna give you a decent idea.
I too use the Sender unit for testing, but also the top Radiator Hose, once the Thermostat opens.
Bruce. >:D
'I'm curious. Where is the best place to aim an IR gun to take a temp reading? On my 41 there is a lot of exposed block to check. But in the newer ones with the valve covers and exhaust manifolds not so much.'
With flat heads with 'tender' valve seats and cylinder heads that are prone to crack, I'd focus on the top of the engine. In my limited experience, I've found that water jacket passages tend to get blocked up at the head gasket, so that coolant can't circulate in the cylinder head; therefore, you're searching for areas of extreme heat at the cylinder head in particular. So old flat heads I've worked on in old 50's boats had electric heat gauges at the very top/front of the engine (inboards mounted on an angle), apparently that's where a lack of circulation in the head would first report a coolant issue. Please keep us in the loop and tell us what you find.
I finally took some temperatures today in five places with a quality Temp Gun:
1. Radiator Hose @ T-Stat
2. Upper Radiator Inlet Hose
3. Lower Radiator Outlet Hose
4. At Temp Switch in front of intake manifold/under AC Comp
5. Middle of Radiator
The Ambient temp was 82°F - I checked it before start up, ~15 min in, and at ~30 min, I let it idle and then did some driving as well. Despite the WATER TEMP light being illuminated by the time I did the 15 min check the temps never even got over 180°F at any of the readings. My understanding is that IR temp guns might read a little low, but regardless it doesn't seem like I'm anywhere near overheating (actually maybe a bit the opposite?). I am using the correct style 180°F T-Stat as pictured which is a "Fail Safe".
Ya the reading could be a little off but that light sender is usually fairly high like at least 230 so if you are reading 180 you would think worst case the coolant in that area could be what 200? which is a long way from 230+.
I'm not sure what they mean by fail safe stats, sounds like something marketing came up with but it is a good sign that its got the disc at the bottom which blocks the bypass port which helps a little bit when things really get cookin.
I can't remember on these can you reasonably disconnect the wire off that sender? Or isn't there enough room under the compressor? If you disconnect it and the light goes out then its a faulty or incorrect sender that is just starting to trigger too soon. If it still comes on then its to the diagrams to see if there is anything other than damaged wire between the sender and light that could cause it to come on.
You've proof that the sender unit is faulty or, as TJ suggests, perhaps a wire to the sender that's causing the problem.. Maybe the "triggering" element in that little original unit is way off the factory calibration and specifications. Leaves me wondering if there is some kind of temporary "work around" such as an electric probe (like a kitchen meat thermometer) that will provide you with an accurate heat reading that does not require you to perform invasive surgery into the cooling system-- and some of these are wireless. The challenge, of course, would require you to know just where to place such a probe and to come up with some accurate way to interpret the reading of normal "metal temperature" at the location of the probe's placement. Perhaps a correlation with your IF gun's reading might serve this purpose, provide peace of mind, and get you back on the road this summer with the least possible effort.
The sender connection point itself is a PITA to get to (Under the AC Comp), however there is an easily accessible connection between the sender and the ignition coil. I will play with that and go from there with inspecting the wiring back into the car. At any rate this is a much more palatable gremlin vs a new overheating engine! I now have some peace of mind that I'm not cooking my engine while I sort things out. Thanks all and I'll report back when I find the fix.