Temperature above 190.....

tvmaster

True Classic
Last time I pulled the fan leads and tested them in bypass, they worked. A relay was installed onnthe second, added fan. I’ll have to make sure it hasn’t failed since that test. And I’ve read several of those posts, hence my concern this temp reading seemed too high. So the change to a higher threshold rad cap doesn’t concern you?
 

Dan Sarandrea (Phila)

Waitin' On Parts...
All other things being equal, the cap pressure rating only affects one thing, which is the temp at which your coolant will boil. The stock cap is .7 bar which roughly translates to 11 psi.

A higher psi cap simply means your coolant will boil at a higher temp. Readily available aftermarket caps typically are rated a little higher, I seem to see 13psi caps offered a lot, so that would be up around .9 bar. I would not want to go higher than that since the system was designed for what it was designed for, and too much pressure in an old Italian classic might blow out something. They don't sell billions of dollars of high blood pressure medicine fer nuthin'. :)

If you are using a .5 bar cap, that would be something around 7-8 psi which would serve to lower the boiling point of your coolant which IMHO is not desirable. After all, boiled coolant is no longer cooling.
 

SuperTopo

True Classic
Bleed your radiator. Then report back. You'd have to have a TON of air in there for the temp switch to not be under water, but I've seen that happen. If there wasn't a ton of air in the radiator, then your thermo switch or relay or some other piece of your fan control is bad. The fact that it cooled back down when you started moving again tells me your thermostat is OK and not stuck closed. The cap pressure wouldn't be the first thing I'd point to in your case.
 

79X1

Daily Driver
Bleed your radiator. Then report back. You'd have to have a TON of air in there for the temp switch to not be under water, but I've seen that happen. If there wasn't a ton of air in the radiator, then your thermo switch or relay or some other piece of your fan control is bad. The fact that it cooled back down when you started moving again tells me your thermostat is OK and not stuck closed. The cap pressure wouldn't be the first thing I'd point to in your case.
Or your car could be like mine was when I bought it. Thermo was stuck closed and no water in the block. Yikes! I thought the temp gauge didn't work, but it was just bone dry. Fixed!
 

tvmaster

True Classic
Or your car could be like mine was when I bought it. Thermo was stuck closed and no water in the block. Yikes! I thought the temp gauge didn't work, but it was just bone dry. Fixed!
No water in the block? What was the fix? The coolant reservoir is 2/3 full, and my FIAT expert racer service guy bled the rad last time I was there, but as an emergency rush-job, so it’s possible he could have let too much air remain?
 
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kmead

Glutton for punishment
No water in the block? What was the fix? The coolant reservoir is 2/3 full, and my FIAT expert racer service guy bled the rad last time I was there, but as an emergency rush-job, so it’s possible he could have let too much air remain?
Wait. How exactly did you resolve your wiring issues? You could still have bad wiring issues which no amount of air or good/bad thermo switch will overcome.

If your wiring was resolved properly, your thermo switch could easily (still) be dead and would be my expectation to be the problem.

Unless I missed it you haven’t actually removed the thermo switch for testing and or replaced it, correct? Or did you replace the thermo switch and I missed that?
 

tvmaster

True Classic
Wait. How exactly did you resolve your wiring issues? You could still have bad wiring issues which no amount of air or good/bad thermo switch will overcome.

If your wiring was resolved properly, your thermo switch could easily (still) be dead and would be my expectation to be the problem.

Unless I missed it you haven’t actually removed the thermo switch for testing and or replaced it, correct? Or did you replace the thermo switch and I missed that?
The switch HAS worked at least twice before, with no changes in wiring. The only change made to the system was Mr. FIAT racer bleeding the rad, and the rad cap update. The wiring all checked out as functional, ambeit amazingly ugly, when tested last (removing both leads from the switch and bridging). So either the relay is shot, a fuse is blown, there isn’t any water over the switch (that can’t be it) or the switch/gauge is wonky. The switch, although just a year old, is likely Basil Fawlty.
 

kmead

Glutton for punishment
The switch HAS worked at least twice before, with no changes in wiring. The only change made to the system was Mr. FIAT racer bleeding the rad, and the rad cap update. The wiring all checked out as functional, ambeit amazingly ugly, when tested last (removing both leads from the switch and bridging). So either the relay is shot, a fuse is blown, there isn’t any water over the switch (that can’t be it) or the switch/gauge is wonky. The switch, although just a year old, is likely Basil Fawlty.
You didn’t fix the wiring to be proper?

Dude.
 

tvmaster

True Classic
You didn’t fix the wiring to be proper?

Dude.
The wiring is proper, dude. Ugly as hell, but where they cut in was fine according to Mr.Fiat. But yes, it's been cleaned up. Lol. I just bridged the fans an hour ago, and they're both working as they should, at least when bypassing the switch. However, I believe there's a problem. Stay tuned for photos.... :(
 
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The switch HAS worked at least twice before, with no changes in wiring. The only change made to the system was Mr. FIAT racer bleeding the rad, and the rad cap update. The wiring all checked out as functional, ambeit amazingly ugly, when tested last (removing both leads from the switch and bridging). So either the relay is shot, a fuse is blown, there isn’t any water over the switch (that can’t be it) or the switch/gauge is wonky. The switch, although just a year old, is likely Basil Fawlty.
If you jumper the thermal switch in the radiator, does the fan come on? That would at least tell you if the wiring was functional and narrow the problem more toward a bad switch or air in the system. You can also test the switch by hooking an ohmmeter to it and put it in a pot of water on the stove with a thermometer. Heat it up and see if it closes at the correct temperature. A stock 74 should not have the fan come on very often unless you are stationary for several minutes or driving through Death Valley in the middle of summer. Mine has never turned on with the car moving.
 

tvmaster

True Classic
If you jumper the thermal switch in the radiator, does the fan come on? That would at least tell you if the wiring was functional and narrow the problem more toward a bad switch or air in the system. You can also test the switch by hooking an ohmmeter to it and put it in a pot of water on the stove with a thermometer. Heat it up and see if it closes at the correct temperature. A stock 74 should not have the fan come on very often unless you are stationary for several minutes or driving through Death Valley in the middle of summer. Mine has never turned on with the car moving.
Yes, I’d like to do this as we possibly discussed last year, but I’m uncertain how to properly remove the switch without splattering fluid all over myself. Still learning. And I guess I‘d need a plug, but it would be just as easy to blow $12 and plug it with a NEW switch? lol. Look at the soon-to-be-published photos. I’m hoping you all have the answer, ‘cause I’m flumuxed.
 
Yes, I’d like to do this as we possibly discussed last year, but I’m uncertain how to properly remove the switch without splattering fluid all over myself. Still learning. And I guess I‘d need a plug, but it would be just as easy to blow $12 and plug it with a NEW switch? lol. Look at the soon-to-be-published photos. I’m hoping you all have the answer, ‘cause I’m flumuxed.
Just drain the radiator below the point where the switch is and you should be OK.
 

tvmaster

True Classic
Ok, maybe this is all fine, or maybe it’s catastrophic, so come one come all and make me believe there’s some hope…

Disconnected the radiator fan wires from the switch, bridged them, and both turned on and sounded great, sucking air from both sides.

Reconnected to the switch, checked the overflow tank, and took the car out for a spirited run, getting the temp up to 180, then parked in the driveway and idled.

Radiator reservoir tank was 2/3 full.

And then it began. At 190 degrees and rising, the flood was under way, as the overflow hose erupted, spewing a steady stream of molten-hot magma on the drive.

When the temp got to about 230, the fans turned on (too high, right?). They ran for two-three minutes, then shut off, not really lowering the temperature very much.

On the good side, the overflow eruption ceased at this point.

Being out of my league, technically, I decided to not wait and see which way the temperature would go next, and shut down the engine.

At what temperature would the rest of you chicken-out and shut the car down?

Finally, while the car‘s in motion and driving, the temperature rarely, if ever, exceeds 190.

Here‘s the order of that story, in photo-form. Thanks folks.

8F66E46E-1941-42CB-936C-82306EB78296.jpeg
D01BB00A-B71C-4976-AB68-FF1EFBFECEBD.jpeg
2B21E298-4BBB-4485-9205-33500BC8B556.jpeg
AD33653C-6EDE-42C8-926D-2CEF66AD2C31.jpeg


Fans turned on and then off at this point…


FAAE6FC3-DFC3-4C92-9A8E-4F18DE5EABDA.jpeg
 
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ng_randolph

Bjorn H
As you know, the thermoswitch for the radiator fans is mounted to the radiator, and the sender for the gauge is mounted to the cylinder head. The temperature will not be the same in those locations. I would suggest that you do your experiment again, but this time instead of idling in the driveway, sit there with your foot on the gas, holding the engine speed at, say, 2000 RPM. This would greatly increase flow through the water pump, and should reduce the temperature difference between head and radiator. At what temperature do the radiator fans cut in (and out) when you do this?

There is a spec for impeller vanes to housing clearance in the water pump (0.8 - 1.3 mm). Whoever installed your water pump may have set the clearance to the wider end of that range, or may have forgotten to check it. Wider clearance will result in less flow, and this would be particularly noticeable at idle. The test suggested above would indicate if insufficient flow is the problem in your case.

And if the problem is with the pump, you need to decide if you want to fix it or live with it. Removing / installing the water pump on a '74 (no access opening between trunk and engine compartment) is a bit of a pain, from what I understand.
 

Dan Sarandrea (Phila)

Waitin' On Parts...
Park it on a reasonably level surface (inside garage is fine) and let it cool off for the night.

Tomorrow....
1. Slide your heater control slider to full hot.
2. Remove cap and replenish coolant in expansion tank if necessary to the typical 3/5 to 2/3 point. Leave cap off for now.
3. Open frunklid, remove the targa top if stowed, and remove the stock rubber plug covering the access hole at the front left side of the radiator hump in the frunk.
4. Place a catch pan/drain pan under the front left corner of the car.
5. In one motion, loosen the rad bleeder a 1/4 to 1/2 turn, count 1-2-3, and then tighten, all the while carefully listening for sounds. You may hear the hissing of escaping air, and/or gurgling of fluid moving inside the rad and/or coolant piping.
[*Note: On my '86 the rad bleeder has a 6mm internal hex head so I use a conventional allen wrench; not sure what the arrangement is on a '74.]
6. Wait 2-3 minutes, then repeat #5. Stop when you get coolant dribbling out and dripping into your pan.
7. Check level in the expansion tank and add if necessary, replace cap.
8. Start and run engine at idle, allow to come up to operating temp (around 190).
9. Throttle to 2500 rpm for 10 sec, drop to idle for 10 sec, back up to 2500 for 10 sec, back to idle for 10 sec. Repeat for two minutes.
10. Turn on heater fan and judge heat outlet air temp. Should be very hot air coming out. Leave heater slider on full hot. Turn off heater fan.
11. Allow to idle and observe temp gauge, waiting to hear fan operation. If you get fan operation at say a temp of 210 or below, we've made progress! If temps rise to around 225 without fan operation, switch off.
12. Switch off and allow to cool for 4-5 hours.
13. Repeat steps 2-11.
14. Let us know what it's doing.
 

tvmaster

True Classic
Park it on a reasonably level surface (inside garage is fine) and let it cool off for the night.

Tomorrow....
1. Slide your heater control slider to full hot.
2. Remove cap and replenish coolant in expansion tank if necessary to the typical 3/5 to 2/3 point. Leave cap off for now.
3. Open frunklid, remove the targa top if stowed, and remove the stock rubber plug covering the access hole at the front left side of the radiator hump in the frunk.
4. Place a catch pan/drain pan under the front left corner of the car.
5. In one motion, loosen the rad bleeder a 1/4 to 1/2 turn, count 1-2-3, and then tighten, all the while carefully listening for sounds. You may hear the hissing of escaping air, and/or gurgling of fluid moving inside the rad and/or coolant piping.
[*Note: On my '86 the rad bleeder has a 6mm internal hex head so I use a conventional allen wrench; not sure what the arrangement is on a '74.]
6. Wait 2-3 minutes, then repeat #5. Stop when you get coolant dribbling out and dripping into your pan.
7. Check level in the expansion tank and add if necessary, replace cap.
8. Start and run engine at idle, allow to come up to operating temp (around 190).
9. Throttle to 2500 rpm for 10 sec, drop to idle for 10 sec, back up to 2500 for 10 sec, back to idle for 10 sec. Repeat for two minutes.
10. Turn on heater fan and judge heat outlet air temp. Should be very hot air coming out. Leave heater slider on full hot. Turn off heater fan.
11. Allow to idle and observe temp gauge, waiting to hear fan operation. If you get fan operation at say a temp of 210 or below, we've made progress! If temps rise to around 225 without fan operation, switch off.
12. Switch off and allow to cool for 4-5 hours.
13. Repeat steps 2-11.
14. Let us know what it's doing.
Step 3: do we have the same holes in our car? I don’t understand which hole you mean.
Step 6: WHERE/WHAT is the coolant dribbling out of, exactly?

Thanks
 

tvmaster

True Classic
As you know, the thermoswitch for the radiator fans is mounted to the radiator, and the sender for the gauge is mounted to the cylinder head. The temperature will not be the same in those locations. I would suggest that you do your experiment again, but this time instead of idling in the driveway, sit there with your foot on the gas, holding the engine speed at, say, 2000 RPM. This would greatly increase flow through the water pump, and should reduce the temperature difference between head and radiator. At what temperature do the radiator fans cut in (and out) when you do this?

There is a spec for impeller vanes to housing clearance in the water pump (0.8 - 1.3 mm). Whoever installed your water pump may have set the clearance to the wider end of that range, or may have forgotten to check it. Wider clearance will result in less flow, and this would be particularly noticeable at idle. The test suggested above would indicate if insufficient flow is the problem in your case.

And if the problem is with the pump, you need to decide if you want to fix it or live with it. Removing / installing the water pump on a '74 (no access opening between trunk and engine compartment) is a bit of a pain, from what I understand.
I imagine the new pump came from MWB, although they won’t confirm which parts they sold WD. So if Matt ships the pump pre-set up to the specs you mention, there you go. If he doesn’t, I’d be surprised if the WD team pre-adjusted it as you describe.
What are the odds the cylinder head sender is damaged? Would a wireless thermometer at the head tell anything - where would you aim it?
 
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Dan Sarandrea (Phila)

Waitin' On Parts...
Step 3: do we have the same holes in our car? I don’t understand which hole you mean.
Step 6: WHERE/WHAT is the coolant dribbling out of, exactly?

Thanks
In the front left corner of the frunk, way up by the hinge. Here's a pic I borrowed from a post by Kevin Cozzo:

1642224282194.png


IIRC Kevin had an issue where the rad bleeder somehow became waaaaay too long and protruded out of the hole, as you can see!

The hole in the sheet metal of the body allows access to a bleeder screw that is mounted in the top left corner of the radiator. When the bleeder screw is backed off/loosened, it allows air to escape from the rad. You know you're done bleeding when there's no more air coming out---when only coolant comes out. And when coolant comes out, it will flow along the left tank of the rad, and drip onto the floor from the front left corner of the rad. That's why you place a drain pan there, to catch it.

Here's a pic of the bleeder screw hole on one of the aftermarket aluminum rads.
20191122_143023_LI.jpg
20191122_143045_LI.jpg
 

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tvmaster

True Classic
Ah, ok. Now I know the hole of which you speak. I’m hoping that does it. And any fluid lost by this gets replenished by filling the reservoir tank in back, yes? Is there any chance I had too much fluid, hence the overflow stopping? I’d still like to hear those fans turn on at a much lower temperature, however…
 

ng_randolph

Bjorn H
I imagine the new pump came from MWB, although they won’t confirm which parts they sold WD. So if Matt ships the pump pre-set up to the specs you mention, there you go. If he doesn’t, I’d be surprised if the WD team pre-adjusted it as you describe.
What are the odds the cylinder head sender is damaged? Would a wireless thermometer at the head tell anything - where would you aim it?
When you buy a "water pump", you are (with rare exceptions) not buying the entire pump. You are buying the impeller side only, as this is where the bearings and seals (the parts that wear out) are. You are reusing your old pump housing. You need both to measure clearance, so you need to check clearance with any new part that you buy. I bought a new water pump in 2013, and as delivered it gave me a clearance of 1.8 mm with my pump housing. I adjusted this down to 0.8 mm.

Your temperature gauge is showing a very believable 190°F under normal operation, climbing to a plausible 225°F (or thereabouts) during extended idling. A damaged cylinder head sender would not be on my list of things to suspect.
 
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