Temps with rebuilt radiator

JimD

JimD

Waiting for Godot...
Moderator
Well I have the 124 put back together and operation with the rebuilt rad, new hoses and new external thermostat. I sat in the garage and let it idle till the fan cycled a few times to be sure that was working.

I am not sure I have made much progress. "Before" pictures would have been a good idea, but I didn't think of it at the time. Here are a couple pictures I took today while taking a short cruise around town. I am probably just letting the non-graduated temp gauge spook me, but here is what I am seeing.

This is where the needle lives while driving around once it is completely warmed up.
124_temp_driving.JPG


This is where it goes if I let it sit and idle in the driveway:
124_temp idle.JPG


I am not happy with that idle indicated temp. Of course, without any numbers it is hard to say what the gauge is reading other than "uncomfortably close to the red for my tastes". I turned off the engine and took my laser thermometer thingy to check temps all around the head and block. Right near the temp sender and the back of the head I got 174F while the needle is where it is shown above. That 174F seems pretty good, but that gauge makes me uncomfortable.

The closer I moved to the front of the engine the warmer the reading topping out at 192F just above the water pump. When I moved around to the passenger side where the exhaust pipes are the block was warmer with temps from 190-210F in various locations. Oddly, the water pump itself registered one of the hottest temps at 224F, bit only if I put the laser in a location near the hub of the pump. Most other spots on the pump were ~190F.

I wish I had taken "before" pictures with the old rad. My recollection is that I started down this repair path when the needle was brushing the red while driving on the highway. I guess I need to get out an do that and see what happens. I didn't have any really long stretches of high speed driving today.
 
Thanks Rod. I looked up how to calibrate a gauge and they talked about using POTs to test the gauge and the sender. It was over my head, but I will keep looking for something I can understand. Water boils at 212F, so I was thinking if I could get the sender into some boiling water I would at least see where it points at 212F.

I tried to remove the sender from the head, but it is in there good. A 24" breaker bar wouldn't budge it... yet anyway. I was frustrated after a few attempts, so I set the breaker down and walked away. It can wait and I know I would have broken something had I kept at it. :)
 
I was going to suggest the boiling water method also.
Take a picture or add a small line to the gauge with tape to indicate the 212° mark.
Takes the guess work out.
 
JimD said:
Water boils at 212F, so I was thinking if I could get the sender into some boiling water I would at least see where it points at 212F.
Click to expand...

Jim, it is incorrect to say water boils at 212F. Water starts to boil at 212F, so don't just plunk it into a pot you've got boiling already, because you don't know how much past 212F it has already gone. The proper procedure is to bring the water to a boil and observe the point where it begins to boil. That will be the 212F mark. Or use a candy thermometer for maximum accuracy.

Pete
 
Pete and Ulix

Thanks for the tips guys. I will give this a try as soon as I can get the damn thing out of the head. I haven't really leaned on it yet, just pulled hard.
 
sometimes stepping away is advice I wish I had been smart enough to do. (more than once).

What they are suggesting with a pot (short name for potentiometer {which is just a resistor that you can control}) is you use it to adjust where your gauge reads. I am sure their wording is more confusing than the actual implication of the idea.
I have done it in the past though I had a bunch of resistors so I just swapped them until I got a reading that I was happy with (with the vehicle at operating (not overheating temps)). I did not have the nice tool you spoke of (thermal temp scanner).
(remember the main goal of the temp gauge is not to tell you the temperature but to tell you when something has changed, though it is comforting to see numbers that make sense most of the time we are only concerned with something that is not "normal".

For example. Most people who setup a race car usually use round gauges where the needle swings all the way around the gauge. and then they mount the gauge to where the needle should point straight up, so in the race a quick glance at them will confirm everything is ok as all the needles are pointing the correct direction.
 
Thanks for the info Rod

I am hoping to find that 212F lives somewhere above the current "high" reading. The external temp of the head at the sender location is only 174F, so that gives me some hope that the gauge is out of spec after 45 years of service. I will report back what I find.
 
Do not rely too much on an infrared thermometer.
The reading of these things depends very much on the type of surface you are measuring (coefficient of emissivity).
So a mirror finish aluminium surface and one painted flat black will show different temps even though they are really the same.

I use mine only for comparing temps on very similar surfaces, such as measuing temps on a race tire at different positions (yes, a probe that you stick into the rubber is much better for this).
 
Hi Ulix,

I was aware of its limitations, but the infrared was all I had to work with. I ordered a probe based thermometer to use for this testing... if I can ever break that sender free. Tried another couple times and it still shows no signs of wanting to leave its home. :(

While we are on the subject. I guess I need to have a ground wire wrapped around the sender for this testing. Right? Will the bare ground wire from a normal 12-2 romex building wire work? I have lots of that. The wire would be stiff enough to fashion a holder to support the sender in the pot of water as well as ground to the block. Thoughts?


UPDATE : WOOOHOOO!! I got the sender out without breaking anything. After I responded to Ulix I said to myself "You haven't tried breaking the sender loose before 10AM yet." So that was the secret, sneak up on it while it was not quite awake enough to fight back.

Actually, I switched from a 24" breaker to my regular 1/2" drive ratchet and tapped on the handle with a 2lb hammer. I had tried that with the breaker, but the universal joint at the end of the breaker has enough give to suck up the hammer blows. The ratchet delivered the blow to the sender.

All is well. I put the sender back in till I get all the test stuff in house and ready to go.
 
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I did some testing today, but the thermometer I bought was off by 7-10F judging by the "when water starts to boil" test. I saw the water bubbling in a couple places in the pot at 205F indicated on the thermometer. Oh well, at least I had something to look at and get a rough idea.

I think the news is mixed. The needle was basically dead center on the gauge at the point "water starts to boil" or 205-207F on the actual thermometer. Ignore that tape, that was from a previous test and I could never get it stuck where I wanted it anyway. I checked the owner and shop manuals. The closest thing I could find to a temperature specification was in the shop manual. It said the thermostat should be fully open at 212F. The owners manual had no temp specs, but offered this advice: "If the needle hovers in the red, stop driving, but do not shut off the engine. Let it idle. If the temperature does not come down, see you local service facility." I guess I will watch for it to get into the red before I start freaking out again.
124_temp_test2.JPG

Just so you know.... This is how I set up the test. I didn't really want to put a heating device in the engine bay, so I used a table with an electric "burner". I used a soldering helper to hold the thermometer and a length of building wire to hold the sender with the tip submerged in the pot. I stripped the end that wrapped around the sender and a section in the middle to attach a ground wire. The cardboard was to deflect some of the heat from the plastic top of the thermometer. I reconfigured this a few times looking for differences in the results, but it was consistent. Hopefully that means I had good continuity.
124_temp_test1.JPG

It got steamy at full boil, it was a little cool in the garage today. The steam is from the pot, not the car. I was even smart enough to disconnect my electric fuel pump before I started playing with this stuff.
124_temp_test3.JPG
 
What did the thermometer show when the water was at full boil?
What did the gauge show at that point?

From my understanding, the temp listed on the thermostat is the temp the engine should run at when warm.
It is the thermostats job to keep the water at this temp under all running conditions.
If the spec for your thermostat is 212°, that is pretty high. On the X1/9, it is around 190° I think.

If the temp at which you too the pic of your gauge was in fact 212°, then the previous pic indicates that your temp when warmed up is higher than 212°.
This is high for an old car and I would analyze further.
 
As far as I know, boiling (pure) water will never go above 212° (slightly depending on air pressure).
So for all this to be correct, you should look at your gauge at full boil, not at "starting to boil".
 
Ulix said:
As far as I know, boiling (pure) water will never go above 212° (slightly depending on air pressure).
So for all this to be correct, you should look at your gauge at full boil, not at "starting to boil".
Click to expand...

Hi Ulix,

Unfortunately, the electric heating element I was using wouldn't push the water temp up much higher than 210F indicated. I let the test run for quite a while after taking that picture. The gauge stayed put at halfway as the temp edged from 205F to 210F. Maybe you are correct that water alone won't get much hotter and the heating element isn't an issue.
 
fiatfactory said:
Just change the sender unit, they go bad after they have been overheated... unlikely to be the gauge.

SteveC
Click to expand...

Thanks Steve. I thought about that, but didn't want to waste the cash without knowing if it was bad. Just looked it up and they are cheap, so I will get a new one. I notice that the gauge senders have red plastic caps now, mine has black which I think denoted that it is pretty old. I found the archived MWB page for the black capped sender and it has the same part number as the red capped one now listed for sale.

I had to replace the oil temp switch last summer because it was bad, so this shouldn't surprise me. My false oil pressure warnings went away with the new sender. For as old as this car is, a lot of the engine bay parts seem original. Most of the hoses still had the old school "sardine can" metal band clamps that look like they are wrapped around a big cotter pin. The hoses I just replaced were REALLY soft.

I will get the new sender and redo the tests. If the results seem the same, I will have to drive it for a while and make sure the behavior is consistent. It is snowing here in STL again and that put an end to my test drives for a while.
 
another thing you might consider. Installing a set of mechanical gauges under the hood out of the way not a lot of $ and if you are questioning the factory gauges you have something to reference to. (see a lot of race car's do this as they spend a lot of time tuning the car with no one behind the wheel watching gauges.
 
Rod Midkiff said:
another thing you might consider. Installing a set of mechanical gauges under the hood out of the way not a lot of $ and if you are questioning the factory gauges you have something to reference to. (see a lot of race car's do this as they spend a lot of time tuning the car with no one behind the wheel watching gauges.
Click to expand...

Rod,

I am not sure where I could put another sender, but I had the same thoughts. Not so much for undr hood testing, but just to get some confirmation of the temps.
 
Well, the news isn't good. At least not in the sense that I have had the radiator cleaned out, replaced the t-stat and hoses, replaced the fan switch in the rad and finally replaced the sender with a new unit last night. I hit the highway for some driving today. The temp gauge read about midway, perhaps a tick higher until I got off the highway to turn back towards home. The gauge jumped up to a little over 3/4 a the light, but it did start to come back down once on the highway again. It came back towards midway on the gauge, but definitely more like 5/8 than 1/2 if you know what I mean.

Of course, I had to get off the highway and sit at a couple lights to get home. The gauge crept closer and closer to the red as I waited. I flipped on the heater once I got thru the lights and was on my subdivision streets. The heater helped bring it from the brink. It never got to the red, but I think I saw it at least this close if not a bit closer than this picture from the last test. :(
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So that is a lot of money and a effort for basically no change. Now it is I obvious I have no clue what I am doing here. When I got the car the rad fan was hardwired to run all the time, maybe I will put the jumper for that mod back in and see what that does while I try to do some more research. I will read back thru everybody's ideas and see if I missed anything.
 
So the first thing is to check the very basics.

Is the car properly timed?
The distributor is only centrifugal advance, correct? Is it advancing properly? If you have a advance timing light you can check its range. Too retarded and it will run hot, perhaps advance it a few degrees.

You have that shiny new carb, is it possibly running lean? How do the plugs look when you pull them?

What is the age of the water pump? Could it be partially corroded or maybe the clearance between the impeller and the body is too great?

Have you run a descaler through the system? Could it be all caked up in the block and head?

How did the inside of the radiator look on the inside when you got it back?

That's all I've got for now.
 
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