[Meerkamp]

My 1972 Series 3 2.25 petrol engine seems to overheat. The gauge moves slowly but constantly into the red within a mile of driving. I changed the water pump first. Didn't help. Then changed the thermostat, didn't help. Then changed the water temp sensor, you guessed it, also didn't help. And finally had the radiator cleaned. Also no effect. Coolant level is as it should be of course. That would have been the easiest. There is no leak as far as I can tell.
The pipe from the thermostat to the radiator gets hot (picture 5862). The pipe on the bottom of the radiator stays cold (picture 5863). So I'm guessing the radiator is blocked or no water is flowing (water pump ?). But the radiator guy filled it with water and said it had a good flow. Maybe the pump I installed was defect. Got it from Rovers North. I tested the thermostat on the stove in a pot of water and it opens at 160F as it should. Also the top pipe couldn't get hot if the thermostat wouldn't open. I turn on the heater and the pipes to the heater get warm too. There just doesn't seem to be a flow through the radiator. Maybe I need to double check that the water pump is working correctly. How can I test the water pump ? Could the gauge be broken. My neighbor has a laser thermometer. Any idea what the temperature at the block should be ? or where I should measure. But it worries me that the pipe on the bottom of the radiator is not getting warm. While the pipe on top is getting hot.
Anyone has any other ideas ? Attached a couple of pictures if that helps.
Thank you
Frank

 

[rdavisinva]

Have you independently verified that the temp gauge is accurate?
An infrared temp gun could be your best friend.

 

[Meerkamp]

Have you independently verified that the temp gauge is accurate?
An infrared temp gun could be your best friend.

I will try that. I assume I measure at the temp sensor ? what should it read ?

 

[RFD110]

More than likely you have a 180°f thermostat. So it should be around that temperature.

 

[Rocky]

The temperature gun is a really good tip. I experienced a similar event. Cause was an internally collapsed radiator.

 

[Meerkamp]

The temperature gun is a really good tip. I experienced a similar event. Cause was an internally collapsed radiator.

Thank you. What confuses me though is that the bottom hose is cold. Shouldn't that be hot too if the car overheats ?

 

[hackneyed1]

My 1972 Series 3 2.25 petrol engine seems to overheat. The gauge moves slowly but constantly into the red within a mile of driving. I changed the water pump first. Didn't help. Then changed the thermostat, didn't help. Then changed the water temp sensor, you guessed it, also didn't help. And finally had the radiator cleaned. Also no effect. Coolant level is as it should be of course. That would have been the easiest. There is no leak as far as I can tell.
The pipe from the thermostat to the radiator gets hot (picture 5862). The pipe on the bottom of the radiator stays cold (picture 5863). So I'm guessing the radiator is blocked or no water is flowing (water pump ?). But the radiator guy filled it with water and said it had a good flow. Maybe the pump I installed was defect. Got it from Rovers North. I tested the thermostat on the stove in a pot of water and it opens at 160F as it should. Also the top pipe couldn't get hot if the thermostat wouldn't open. I turn on the heater and the pipes to the heater get warm too. There just doesn't seem to be a flow through the radiator. Maybe I need to double check that the water pump is working correctly. How can I test the water pump ? Could the gauge be broken. My neighbor has a laser thermometer. Any idea what the temperature at the block should be ? or where I should measure. But it worries me that the pipe on the bottom of the radiator is not getting warm. While the pipe on top is getting hot.
Anyone has any other ideas ? Attached a couple of pictures if that helps.
Thank you
Frank
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All of this happens within a mile? Can it really get that hot that fast? Couldn't it just be a voltage issue at the gauge?

 

[RFD110]

Honestly if your engine is truly overheating that quickly, then you are having an issue with a head gasket or internal issue, where the combustion gases are getting to the coolant.
You can get a test for detecting exhaust gases in the coolant.
First though, I’d check the temp of the thermostat housing, upper and lower hoses with a infrared temp sensor.
If the upper hose is hot and the lower isn’t, then I’d suspect the radiator. If it’s original, then it probably needs to be recored or replaced. Just having it cleaned probably isn’t enough.

 

[Uncle Douglas]

As suggested several times above a cheap IR gun would answer all questions in a few moments. With an IR gun you can see blockages (cold spots) in a radiator. You can also establish temp drop/efficiency of a radiator by comparing inlet and outlet temps. Would offer that no engine makes enough heat to overheat in just a mile. If you remove your radiator cap and drive a mile and coolant geysur's up then you are pressurizing the coolant system with combustion gasses and have a blown headgasket, cracked head, or a cracked block. An infared heat gun is the diagnostic tool you need.

Cleaning a radiator means different things to different people. It used to mean having one of the tanks sweated off and a small piece of straight wire forced through ea of the capillary tubes called rodding it out, this combined with a weak acid flush returned radiators to like new efficiency. Today cleaning it usually simply means reverse flushing it, which is basically worthless except as maintenance, if there is already a problem, flushing has never worked/fixed one for me.
If someone has ever poured radiator stop leak into the radiator its ruined, get another.

 

[Uncle Douglas]

Looking @ your pictures it appears you have a couple shims between your lower coolant hose and hose clamp.May just be the photo angle and likely just remnants of parts label.
If they are shims, thats a bad idea, clamp cannot apply pressure uniformly and will leak eventually.

 

[Meerkamp]

All of this happens within a mile? Can it really get that hot that fast? Couldn't it just be a voltage issue at the gauge?

Good point. How can I test the gauge ? What should the voltage show ?

 

[Meerkamp]

Looking @ your pictures it appears you have a couple shims between your lower coolant hose and hose clamp.May just be the photo angle and likely just remnants of parts label.
If they are shims, thats a bad idea, clamp cannot apply pressure uniformly and will leak eventually.

Those are parts labels. Thank you though.

 

[hackneyed1]

Good point. How can I test the gauge ? What should the voltage show ?

(someone correct me if the following is incorrect for a '72.) Get access to the back of the gauge and check for voltage when in neutral and the engine revving. If you are charging excessively and the gauge is not connected to a stabilizer, the gauge will read high. The stabilizer provides a steady 10 volts to the gauge regardless of charging system output. Of course, usually the fuel gauge is connected to the same stabilizer.

 

[Meerkamp]

Little update on my mysterie for anyone interested. And thank you to all who have commented. I am not a mechanic and really appreciate the tips and ideas.
I got a thermometer and turns out the engine is not overheating. Reads 160F at the Thermostat. Which is when it opens. I had tested that on my stove top before. Between 140F and 180F at various spots on the engine block. 150F at the radiator cap on top and gradually goes down to 70-80F at the bottom of the radiator.
So seems the issue is with the gauge. When the car sits in my driveway and idles the gauge eventually goes right into the middle of the N sign which is perfect. And stays there. Then when I drive it moves up towards the red and even into the red. But when I check the temperature at the thermostat it stays at 160F. Same with temp readings at other spots of the engine and radiator. Readings are the same as in my driveway only the gauge indicates differently. So the engine doesn't seem to get hotter. But the somehow the gauge behaves differently when driving vs. sitting in my driveway.
I recall a conversation with my mechanic about a voltage stabilizer and I don't believe I have one. Maybe that could fix it ? Any other suggestions ?
Thanks again for everyones help.

 

[hackneyed1]

Little update on my mysterie for anyone interested. And thank you to all who have commented. I am not a mechanic and really appreciate the tips and ideas.
I got a thermometer and turns out the engine is not overheating. Reads 160F at the Thermostat. Which is when it opens. I had tested that on my stove top before. Between 140F and 180F at various spots on the engine block. 150F at the radiator cap on top and gradually goes down to 70-80F at the bottom of the radiator.
So seems the issue is with the gauge. When the car sits in my driveway and idles the gauge eventually goes right into the middle of the N sign which is perfect. And stays there. Then when I drive it moves up towards the red and even into the red. But when I check the temperature at the thermostat it stays at 160F. Same with temp readings at other spots of the engine and radiator. Readings are the same as in my driveway only the gauge indicates differently. So the engine doesn't seem to get hotter. But the somehow the gauge behaves differently when driving vs. sitting in my driveway.
I recall a conversation with my mechanic about a voltage stabilizer and I don't believe I have one. Maybe that could fix it ? Any other suggestions ?
Thanks again for everyones help.
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So I'm guessing that you might not own a digital multimeter. Grab a cheap one for Harbor Freight (the even have coupons for them for free), but even the most expensive one is like $10. No need to Fluke out on this. Turn it on, set it to 20 VDC and touch the terminals on the back of the gauge with the leads. Take a reading with the engine revving up. My assumption is that the alternator output at idle is lower than at throttle and that's why your gauge starts reading higher because you do not have any/a working voltage stabilizer. The OE (original equipment) stabilizer was a wound coil of wires in a box about the size of your thumb. Both the gas gauge and the temp gauge are hooked to it. The gauges read a measure of resistance of the fuel level sender and the temp sensor. In order to display a consistent reading at a set resistance, the input voltage must remain constant. And Rovers (especially the ones with generators instead of alternators) greatly vary the system voltage between idle and throttle. A higher input voltage at the same resistance would show a higher gauge reading. The stabilizer clips the voltage at a steady 10v, taking voltage fluctuations out of the question. Assuming that you check and see that you need a voltage stabilizer, my advice is not to replace it with the old mechanical type, but rather go solid state. The SS component that does the trick is only a buck or two on ebay or amazon but you'd need to solder the ends on yourself. Or places like Moss Motors sells them ready to install for about $30 (last I checked).

 

[RFD110]

This is what you appear to be missing

148876 | Voltage Stabiliser Gauges Ser3 - Land Rover Part 148876

More than likely it was just bypassed, and is still screwed in to the cowling, behind the gauges.


Sent from my iPad using Tapatalk

 

[Meerkamp]

So I'm guessing that you might not own a digital multimeter. Grab a cheap one for Harbor Freight (the even have coupons for them for free), but even the most expensive one is like $10. No need to Fluke out on this. Turn it on, set it to 20 VDC and touch the terminals on the back of the gauge with the leads. Take a reading with the engine revving up. My assumption is that the alternator output at idle is lower than at throttle and that's why your gauge starts reading higher because you do not have any/a working voltage stabilizer. The OE (original equipment) stabilizer was a wound coil of wires in a box about the size of your thumb. Both the gas gauge and the temp gauge are hooked to it. The gauges read a measure of resistance of the fuel level sender and the temp sensor. In order to display a consistent reading at a set resistance, the input voltage must remain constant. And Rovers (especially the ones with generators instead of alternators) greatly vary the system voltage between idle and throttle. A higher input voltage at the same resistance would show a higher gauge reading. The stabilizer clips the voltage at a steady 10v, taking voltage fluctuations out of the question. Assuming that you check and see that you need a voltage stabilizer, my advice is not to replace it with the old mechanical type, but rather go solid state. The SS component that does the trick is only a buck or two on ebay or amazon but you'd need to solder the ends on yourself. Or places like Moss Motors sells them ready to install for about $30 (last I checked).

Is this the right part ? 131-555 Solid State Voltage Stabilizer, negative ground | Moss Motors

 

[hackneyed1]

Is this the right part ? 131-555 Solid State Voltage Stabilizer, negative ground | Moss Motors

affirmative.

 

[Rocky]

Thank you. What confuses me though is that the bottom hose is cold. Shouldn't that be hot too if the car overheats ?

Not if the radiator is blocked and coolant cannot flow.

 

[Meerkamp]

Good point. How can I test the gauge ? What should the voltage show ?

You were right. I changed the Voltage Stabilizer and now it works just fine. Thanks for the tip. Frank