Pls car gurus, I want to find out if my car has its thermostat removed. Its a Nissan primera 1998 2.0i. It doesn't show any sign of overheating. The temperature gauge usually rise and.then stay somewhere around the middle no matter how much I drive. Pls ..

Plus, I want to know where to find the scanner port. I plan to scan the car cos the check light is on.

apexquest:
Pls car gurus, I want to find out if my car has its thermostat removed. Its a Nissan primera 1998 2.0i. It doesn't show any sign of overheating. The temperature gauge usually rise and.then stay somewhere around the middle no matter how much I drive. Pls ..

Plus, I want to know where to find the scanner port. I plan to scan the car cos the check light is on.

How long does it take for the gauge to reach midpoint?

The thermostat if working properly will usually regulate the cooling fan. This automatically switches on the cooling fan when the engine reaches a temperature pre-set by the vehicle manufacturer.

If the thermostat has been removed there may have been a previous overheating problem with the car. To get round this some mechanics will amend the electrics to ensure that the cooling fan is on all the time - a bad move. This is something common on some cars in Nigeria e.g Landrover Freelanders.

I always carry out a cooling fan test (among others) before I purchase a used car.

Does your car currently overheat or is the cooling fan on all the time?

billy187:


How long does it take for the gauge to reach midpoint?

Up to 5mins or so...

apexquest:

The two fans starts working as soon as I turn on the vehicle,.even in the morning..

Mlud:
The thermostat if working properly will usually regulate the cooling fan. This automatically switches on the cooling fan when the engine reaches a temperature pre-set by the vehicle manufacturer.

If the thermostat has been removed there may have been a previous overheating problem with the car. To get round this some mechanics will amend the electrics to ensure that the cooling fan is on all the time - a bad move. This is something common on some cars in Nigeria e.g Landrover Freelanders.

I always carry out a cooling fan test (among others) before I purchase a used car.

Does your car currently overheat or is the cooling fan on all the time?

The two fans starts working as soon as I turn on the vehicle,.even in the morning.. It doesn't overheat.. I have done straight 30 to 40 minutes drive on 3 occasions, didn't cross the half way on gauge.

apexquest:

Up to 5mins or so...

Check again my brother, in my opinion, 5 minutes for a running engine is somehow high. Well, maybe because I drive V6 cars.

apexquest:

Up to 5mins or so...

Up to? I guess its in there somewhere; 'cos it will take forever to reach midpoint if that was not the case

apexquest:

The two fans starts working as soon as I turn on the vehicle,.even in the morning.. It doesn't overheat.. I have done straight 30 to 40 minutes drive on 3 occasions, didn't cross the half way on gauge.

Here are a few simple steps that would help you know if your car's thermostat has been removed

Step 1: Open your car bonnet or hood, first thing in the morning.

Step 2: Start the car.

Step 3: Go to the front of the car and observe whether the fans start working immediately or not.


Decision Rule:

If the fans start working immediately you start the car first thing in the morning (at cold start), know that the car's thermostat has been removed.

If on the other hand, the fans do not come on immediately at cold start (that is, if it took some time after cold start before the fans come on), then you are safe. That means your car's thermostat is still intact.

You might want to consult you car service manual for this.

Most recent cars, the ECU controls the fan and the fan speed. If you thermostat is removed, there should be an engine light on the dash board.

When thermostat is removed, the coolant flow into the engine system immediately you start the engine, the temperature sensor upstream of the thermostat measures the temperature, the ECU which is constantly in communication with the temp sensor notice the low temperature hence throw a code of thermostat stuck in open position. with this you will know if the thermostat is not there or stock in open position. In this case you will not have an overheating problem and your fan MIGHT not spin at lower temperature depend on the car operation.

You can only have overheating problem if your thermostat is stuck in closed position or not fully open when call open.

FlyboyZee:


Here are a few simple steps that would help you know if your car's thermostat has been removed

Step 1: Open your car bonnet or hood, first thing in the morning.

Step 2: Start the car.

Step 3: Go to the front of the car and observe whether the fans start working immediately or not.


Decision Rule:
D
If the fans start working immediately you start the car first thing in the morning (at cold start), know that the car's thermostat has been removed.

If on the other hand, the fans do not come on immediately at cold start (that is, if it took some time after cold start before the fans come on), then you are safe. That means your car's thermostat is still intact.

Will do that first thing tomorrow morning .. Thanks.

Mlud:
The thermostat if working properly will usually regulate the cooling fan. This automatically switches on the cooling fan when the engine reaches a temperature pre-set by the vehicle manufacturer.

If the thermostat has been removed there may have been a previous overheating problem with the car. To get round this some mechanics will amend the electrics to ensure that the cooling fan is on all the time - a bad move. This is something common on some cars in Nigeria e.g Landrover Freelanders.

I always carry out a cooling fan test (among others) before I purchase a used car.

Does your car currently overheat or is the cooling fan on all the time?

wrong !!!!!!!!!

domack99:
You might want to consult you car service manual for this.

Most recent cars, the ECU controls the fan and the fan speed. If you thermostat is removed, there should be an engine light on the dash board.

When thermostat is removed, the coolant flow into the engine system immediately you start the engine, the temperature sensor upstream of the thermostat measures the temperature, the ECU which is constantly in communication with the temp sensor notice the low temperature hence throw a code of thermostat stuck in open position. with this you will know if the thermostat is not there or stock in open position. In this case you will not have an overheating problem and your fan MIGHT not spin at lower temperature depend on the car operation.

You can only have overheating problem if your thermostat is stuck in closed position or not fully open when call open.

wrong!!!!

thermostat and thermo switch are two different entity !!!!
they work to complement each other works.
Thermo switch is an electrical switch that trigger the relay that switch on the fan when the ecu receives signal of engine coolant temperature attaining a certain threshold.

thermostat and thermo switch are two different entity !!!!
they work to complement each other works.
Thermo switch is an electrical switch that trigger the relay that switch on the fan when the ecu receives signal of engine coolant temperature attaining a certain threshold.
while a thermostat is purely a purely mechanical device that open or close the flow of coolant to the the radiator in order for the engine to maintain the necessary optimum engine temperature eg 95 c for most japanese cars.

honmusa:
thermostat and thermo switch are two different entity !!!!
they work to complement each other works.
Thermo switch is an electrical switch that trigger the relay that switch on the fan when the ecu receives signal of engine coolant temperature attaining a certain threshold.
while a thermostat is purely a purely mechanical device that open or close the flow of coolant to the the radiator in order for the engine to maintain the necessary optimum engine temperature eg 95 c for most japanese cars.

Adding to what @honmusa stated. Very correct! The thermostat is a purely mechanical switch (speaking analogously) which opens or closes to allow more or less coolant flow depending on the temperature level of the coolant flowing through the engine. Whereas thermo switch (now speaking purely electrically) is simply an electrical switch that responds to changes in temperature which the ECU can communicate with.

At cold start, the engine coolant thermostat remains CLOSE. After starting the car and the engine starts running it begins to heat up...the coolant inside gains the heat and heats up correspondingly. At this point, the engine thermostat heats up as well and begins to change position from been fully close to partially close and then fully OPEN when the temperature is optimum. Once the thermos begins to open cool water begins to flow into the engine to cool it and thereby bringing the engine temperature to normal. This happens when the thermostat is fully open i.e. when the coolant temperature is 95degC.

Now, back to the question on how to know whether the thermostat is still intact or has been removed.

1. Pop up the hood;

2. Start the engine

3. Look carefully in front of the engine between the radiator and the engine. You will see two big hoses going into the engine from the radiator. One of them is usually located at the upper side of the radiator while the other is at the bottom. They're both usually close together at the engine side and enters the engine. One of them takes hot coolant away from the engine, while the other takes cool coolant into the engine when the thermostat is partially or fully open.

4. After locating the hoses, carefully and constantly monitor how hot or cold the hoses are by feeling them with your hands. After say 1-2 mins you will observe that one hose will change from being cool to warm then while the other remains cold. After say 5mins, the hose that was cold should become or feel warm to touch. After say 5-10 minutes, both hoses should be just about the same temperature. If what I described so far happens then your thermostat is intact and working fine.

5. If the as you start the engine and feel the hoses with your hand and they both have the same temperature throughout the time or one remains hot and the other remains cold after 5-10mins? It then mean two things - (i) It's either the thermostat is stuck in CLOSE position, i.e when one hose remains cold and the other hot after the said time period (5-10mins) or (ii) it is stuck OPEN or has been REMOVED, i.e. when both hoses maintains the same temperature change, of equal amounts, all through the time period, i.e are both hot or cold at the same time, from when the engine was started to when it became hot.

6. I hope this little 'layman' explanation answered your question??

lonelydora:


Check again my brother, in my opinion, 5 minutes for a running engine is somehow high. Well, maybe because I drive V6 cars.

3mins should do but if he says 5, i guess there is a thermostat in there. Without thermostat and on idle, it will take forever (just kidding maybe 30mins) to near but will not reach operating temp.

apexquest:

The two fans starts working as soon as I turn on the vehicle,.even in the morning.. It doesn't overheat.. I have done straight 30 to 40 minutes drive on 3 occasions, didn't cross the half way on gauge.

What about driving 12hrs non stop with A/C on or staying stand still in a hold up on a hot day with A/C on for 1hr.

Thats when you really know your car does not overheat.

Mlud:
The thermostat if working properly will usually regulate the cooling fan. This automatically switches on the cooling fan when the engine reaches a temperature pre-set by the vehicle manufacturer.

If the thermostat has been removed there may have been a previous overheating problem with the car. To get round this some mechanics will amend the electrics to ensure that the cooling fan is on all the time - a bad move. This is something common on some cars in Nigeria e.g Landrover Freelanders.

I always carry out a cooling fan test (among others) before I purchase a used car.

Does your car currently overheat or is the cooling fan on all the time?

I will like to make a correction so that readers will not have it stuck in their brains.

Thermostat does not control or regulate the cooling fan, the temperature sensor is the one that does that. It does that by sensing when temp is going high so it switches on the fan by means of a relay.

A simple logic to know that for sure is looking at cars with viscous cooling fans as example. In such case, the fan is purely a mechanical one so the thermostat has no way to regulate it?

What is all this dogon turanci about?

With the engine cold, Simply loosen the thermostat housing and see if the thermostat is there.

Alternatively, with the engine cold, remove the top radiator hose from the thermostat housing and carefully poke through with a long screw driver or engine oil dip stick to see if it goes through. If you feel an obstruction where the thermostat sits then its most likely that its still there.

1998 Nissan Primera. If you didn't buy this car as a direct "Tokunmbo", its most likely that the thermostat has been removed by the previous owner.

Car-doctor.

adanny01:


What about driving 12hrs non stop with A/C on or staying stand still in a hold up on a hot day with A/C on for 1hr.

Thats when you really know your car does not overheat.

Uhmmmm...I havent had any reason to drive for 12hrs or stay one hr at hold up.

adanny01:


I will like to make a correction so that readers will not have it stuck in their brains.

Thermostat does not control or regulate the cooling fan, the temperature sensor is the one that does that. It does that by sensing when temp is going high so it switches on the fan by means of a relay.

A simple logic to know that for sure is looking at cars with viscous cooling fans as example. In such case, the fan is purely a mechanical one so the thermostat has no way to regulate it?

But y will the temp sensor trigger the cooling fans to run early in the morning at cold start??

apexquest:

But y will the temp sensor trigger the cooling fans to run early in the morning at cold start??

Any car that its fan comes on during cold start has been bypassed.

Infact, the temp sensor does not trigger the fans. There is a fan switch replay which is embedded in the ECU that triggers the fan.

Temp sensor only reads coolant temperature and relates it to the ECU or fan switch. The fan relay switch is programmed to switch on the fan only when the temp sensor reads a perticular temp say 100 degrees centigrade. In the morning during cold start the temp sensor reads say 40 degrees so the fan remains off until temp reaches 100.

On the other hand, the thermostat mechanically close stopping circulation of coolant. It is designed to open when it sense coolant temperature is above its set point say 85 degrees.

What this means is that the minimum operating temp for that engine is 85 and the maximum is 100. The normal engine operating temp range is now 85-100.

Revision: if temp is below 85 thermostat shuts close and if temp goes above 100 fan comes on.

apexquest:

Uhmmmm...I havent had any reason to drive for 12hrs or stay one hr at hold up.

Have you done this...

FlyboyZee:

Here are a few simple steps that would help you know if your car's thermostat has been removed
Step 1: Open your car bonnet or hood, first thing in the morning.
Step 2: Start the car.
Step 3: Go to the front of the car and observe whether the fans start working immediately or not.
Decision Rule:
If the fans start working immediately you start the car first thing in the morning (at cold start), know that the car's thermostat has been removed.
If on the other hand, the fans do not come on immediately at cold start (that is, if it took some time after cold start before the fans come on), then you are safe. That means your car's thermostat is still intact.

What did you observe? so that others can learn? At least this is one of the easiest and no-frills way to find out...

davo3286:


Adding to what @honmusa stated. Very correct! The thermostat is a purely mechanical switch (speaking analogously) which opens or closes to allow more or less coolant flow depending on the temperature level of the coolant flowing through the engine. Whereas thermo switch (now speaking purely electrically) is simply an electrical switch that responds to changes in temperature which the ECU can communicate with.

At cold start, the engine coolant thermostat remains CLOSE. After starting the car and the engine starts running it begins to heat up...the coolant inside gains the heat and heats up correspondingly. At this point, the engine thermostat heats up as well and begins to change position from been fully close to partially close and then fully OPEN when the temperature is optimum. Once the thermos begins to open cool water begins to flow into the engine to cool it and thereby bringing the engine temperature to normal. This happens when the thermostat is fully open i.e. when the coolant temperature is 95degC.

Now, back to the question on how to know whether the thermostat is still intact or has been removed.

1. Pop up the hood;

2. Start the engine

3. Look carefully in front of the engine between the radiator and the engine. You will see two big hoses going into the engine from the radiator. One of them is usually located at the upper side of the radiator while the other is at the bottom. They're both usually close together at the engine side and enters the engine. One of them takes hot coolant away from the engine, while the other takes cool coolant into the engine when the thermostat is partially or fully open.

4. After locating the hoses, carefully and constantly monitor how hot or cold the hoses are by feeling them with your hands. After say 1-2 mins you will observe that one hose will change from being cool to warm then while the other remains cold. After say 5mins, the hose that was cold should become or feel warm to touch. After say 5-10 minutes, both hoses should be just about the same temperature. If what I described so far happens then your thermostat is intact and working fine.

5. If the as you start the engine and feel the hoses with your hand and they both have the same temperature throughout the time or one remains hot and the other remains cold after 5-10mins? It then mean two things - (i) It's either the thermostat is stuck in CLOSE position, i.e when one hose remains cold and the other hot after the said time period (5-10mins) or (ii) it is stuck OPEN or has been REMOVED, i.e. when both hoses maintains the same temperature change, of equal amounts, all through the time period, i.e are both hot or cold at the same time, from when the engine was started to when it became hot.

6. I hope this little 'layman' explanation answered your question??

This morning i tried the radiator hose method. I kept touching both hoses while waiting for temp gauge to rise to mid point.
Observation
I observed that the hose at the top of the radiator had become very warm while the lower hose had remain cool.
Nevertheless both fans starting running the moment I turned on the car at cold start.
What sayeth thou about these

FlyboyZee:


Here are a few simple steps that would help you know if your car's thermostat has been removed

Step 1: Open your car bonnet or hood, first thing in the morning.

Step 2: Start the car.

Step 3: Go to the front of the car and observe whether the fans start working immediately or not.


Decision Rule:

If the fans start working immediately you start the car first thing in the morning (at cold start), know that the car's thermostat has been removed.

If on the other hand, the fans do not come on immediately at cold start (that is, if it took some time after cold start before the fans come on), then you are safe. That means your car's thermostat is still intact.

what are the effect of a removed or disconnected thermostat

The Mistubishi i had at home when bought the fan doesnot roll until i have moved for some minute then it starts to roll but after the service the mechanic disonnected something that looks like a square .but now when you start it ,the fan starts to roll immediately.

Pls is there any side effect ??

Hello Guyz,Please is there any mechanic that i can learn from,would like to learn about cars,learn how to repair cars and know more about cars.Anyone to link me up ,Am a student who is ready to learn.

apexquest:

This morning i tried the radiator hose method. I kept touching both hoses while waiting for temp gauge to rise to mid point.
Observation
I observed that the hose at the top of the radiator had become very warm while the lower hose had remain cool.
Nevertheless both fans starting running the moment I turned on the car at cold start.
What sayeth thou about these

Your observation about the hoses is right. With the upper hose becoming warm before the lower hose indicates that your thermostat is intact (hasn't been removed) but whether it would respond correctly to rise/fall in temperature is another topic entirely. As for your fan running the moment you turned ON the car testifies two things - either some mechanic has removed and bypassed the fan relay using wire to connect it directly or your AC button or switch was turned ON before you switched off the ignition the previous time.

An electrical relay has two section - the 'coil side' and the 'switch side' or 'contact' (which can be N.O -normally open or N.C -normally close or a combination of both). Supplying voltage to the coil causes the contact to either close (N.O) or open (N.C)

FlyboyZee:


Here are a few simple steps that would help you know if your car's thermostat has been removed

Step 1: Open your car bonnet or hood, first thing in the morning.

Step 2: Start the car.

Step 3: Go to the front of the car and observe whether the fans start working immediately or not.


Decision Rule:

If the fans start working immediately you start the car first thing in the morning (at cold start), know that the car's thermostat has been removed.

If on the other hand, the fans do not come on immediately at cold start (that is, if it took some time after cold start before the fans come on), then you are safe. That means your car's thermostat is still intact.

I know this thread is 7yrs old but I'll still reply and correct your flawed understanding about cars' cooling system anyway so that anyone reading this in 2022 and beyond will get the correct logic.

Your car's thermostat whether working or not, does not control your cooling fan. There's a sensor called the Engine Coolant Temperature (ECT) which exclusively does that by sensing when the coolant is hot and switches on the fan or when it's cold and switches off the fan. All of these processes happen automatically.

In case you want to know whether your thermostat is fully functioning while installed, kindly carry out these steps. While your car is cold, open the radiator cap and start the engine. Cold engine will have its thermostat closed so no coolant will flow through the engine until it's hot again. Through this process, there won't be any movement of the coolant via the radiator cap. However, if you see air bubbles and movement of coolant from the radiator cap, know that the thermostat is stuck open in the engine and not working at all.

I hope this helps.