Toyota Pickup Engine Temp Guage

[chownah]

Well I burned up my pickup last night....not too bad....only fried two pistons...10,000 baht more or less...I'll know the bottom line in a couple of days. I watch the temperature guage as a regular driving habit and it has never gotten beyond half way to the small red zone which is on the right and in fact that is where it was when it went. In the US half way to the red zone means there is no problem and you are well within operating temperature. I had my wife ask the mechanic about checking the temp guage because it never went past half way and he told her that half way meant too hot. This is completely contrary to everything I have ever read or experienced. Now I'll admit that my experience is all in the US with gas powered vehicles and my Toyota is diesel. Is he right?

[bino]

Well I burned up my pickup last night....not too bad....only fried two pistons...10,000 baht more or less...I'll know the bottom line in a couple of days.  I watch the temperature guage as a regular driving habit and it has never gotten beyond half way to the small red zone which is on the right and in fact that is where it was when it went.  In the US half way to the red zone means there is no problem and you are well within operating temperature.  I had my wife ask the mechanic about checking the temp guage because it never went past half way and he told her that half way meant too hot.  This is completely contrary to everything I have ever read or experienced.  Now I'll admit that my experience is all in the US with gas powered vehicles and my Toyota is diesel.  Is he right?

I've no experience with diesel vehicles, but halfway to the red zone... nowhere near the red should be safe. The red zone is definitely there for a reason!

My temp guage in my car likes to sit at just under halfway. Creeps up to half when sitting in traffic with AC on max. Never anywhere near the red zone which is the top 20%.

Are you sure that you weren't misunderstood by wife / mechanic? Halfway INTO the red zone? That would surely be too hot!

[pluto_manibo]

The temperature gauge should be halfway of the gauge. This is normal running temperature. The needle should never go above halfway under normal circumstances. Red zone= overheating.....

[Ajarn]

My isuzu diesel is normallly at 50% on the heat gauge, too. In the rain, it drops to about 30-40% At 60%, the a/c stops being cold. This happened twice, after sitting for a long time in hot weather with the engine running...

[ozzydom]

Well I burned up my pickup last night....not too bad....only fried two pistons...10,000 baht more or less...I'll know the bottom line in a couple of days.  I watch the temperature guage as a regular driving habit and it has never gotten beyond half way to the small red zone which is on the right and in fact that is where it was when it went.  In the US half way to the red zone means there is no problem and you are well within operating temperature.  I had my wife ask the mechanic about checking the temp guage because it never went past half way and he told her that half way meant too hot.  This is completely contrary to everything I have ever read or experienced.  Now I'll admit that my experience is all in the US with gas powered vehicles and my Toyota is diesel.  Is he right?

<{POST_SNAPBACK}>

Guages in LoS built vehicles are not great quality chownah, and in this climate ,good thermostats and guages can save you a lot of cash. It is easy to check the operation of both.With your temp guage ,just take the sender unit or anode out of the block, boil some water in a pot and insert sender unit /anode and see where your guage reads (it should be in the red zone) then let it cool for 3-4 minutes and recheck ,it oughta now be in the driving zone.

Thermostats are the most important item as it controls the engine temp by opening up at about 180-190f ,always check even a new one just remove it ,put it in a pot on the stove and observe ,it should start to open just before simmer and be fully open before water boils.if you have a good cooking thermometre in the kitchen drawer its even easier. plus ALWAYS use a top brand rust inhibitor, buy it yourself, dont leave it to a mechanic to put in,they have a habit of using the cheapest and charging the dearest. Inhibitor should come from the dealer as it is manufactured to suit the particular alloy in your particular engine.

[chownah]

Thanks one and all for reassuring me that half way SHOULD be OK just like always. I'm going to take Ozzydom's advise and calibrate my temperature guage and check the thermostat's functioning. Also I think I'll buy an add on temperature guage....one that actually shows the temperature...I think I'll check that one too before I install it....hope I can find one with its own light so I can read it at night.

One more thing. My wife and I have an ongoing arguement about this. The radiator has a tube that connects to a small holding tank right next to it. This tank has markings on the side to show when it is full. I'm familiar with these...all cars have them except old ones...I think. I told my wife that to check the water level you look at the level in the tank....she says you open the radiator cap and check it there. Now that I've burned up my first engine I'm wondering if she is right.

[ozzydom]

My isuzu diesel is normallly at 50% on the heat gauge, too. In the rain, it drops to about 30-40% At 60%, the a/c stops being cold. This happened twice, after sitting for a long time in hot weather with the engine running...

<{POST_SNAPBACK}>

A pretty normal occurence ajarn,the air-con has a cooling radiator /or utilises the main one and it relies on the flow of air through it while moving for cooling and efficiencyso when stopped for any length of time ,coolent temp in radiator rises and a/c efficiency drops.Some a/c compressors have an overheating cut-out which auto reset when temp goes back down..

[ozzydom]

Thanks one and all for reassuring me that half way SHOULD  be OK just like always.  I'm going to take Ozzydom's advise and calibrate my temperature guage and check the thermostat's functioning.  Also I think I'll buy an add on temperature guage....one that actually shows the temperature...I think I'll check that one too before I install it....hope I can find one with its own light so I can read it at night.

One more thing.  My wife and I have an ongoing arguement about this.  The radiator has a tube that connects to a small holding tank right next to it.  This tank has markings on the side to show when it is full.  I'm familiar with these...all cars have them except old ones...I think.  I told my wife that to check the water level you look at the level in the tank....she says you open the radiator cap and check it there.  Now that I've burned up my first engine I'm wondering if she is right.

<{POST_SNAPBACK}>

best to check both when cold chownah, the plastic one is a reserve cum header tank .

[Thetyim]

Agree with all the above but will add just one thing.

The temp gauge measures your water temperature if you have little or no water the gauge will not give a warning.

This might explain your mechanical disaster .

It is best to check the water level in the rad and not relie on the expansion bottle as any leak in the system will not show up.

[bino]

One more thing.  My wife and I have an ongoing arguement about this.  The radiator has a tube that connects to a small holding tank right next to it.  This tank has markings on the side to show when it is full.  I'm familiar with these...all cars have them except old ones...I think.  I told my wife that to check the water level you look at the level in the tank....she says you open the radiator cap and check it there.  Now that I've burned up my first engine I'm wondering if she is right.

This has always perplexed me also, considering that the hose outlet nipple is above the sealing surface of the radiator cap. It is easy enough to fugure out how the overheating water from the radiator gets into the tank, since the radiator cap is spring loaded and will open at 15 psi or whatever. Defies logic as to how the cold water gets back into the radiator as the radiator cap pressing shut would prevent this. There is no process of physics that makes sense to me, IE siphon action,etc. Can anyone explain how the water gets from the tank into the radiator / cooling system?

Hence, I've never trusted the holding tank and always opened the radiator cap once in a while to look inside and ensure that the water level is above the cooling fins (When the engine is cold in the morning of course- never open hot). Certainly can't hurt to check and doesn't take but a few more seconds of time.

Edited May 20, 2005 by bino

[chownah]

One more thing.  My wife and I have an ongoing arguement about this.  The radiator has a tube that connects to a small holding tank right next to it.  This tank has markings on the side to show when it is full.  I'm familiar with these...all cars have them except old ones...I think.  I told my wife that to check the water level you look at the level in the tank....she says you open the radiator cap and check it there.  Now that I've burned up my first engine I'm wondering if she is right.

<{POST_SNAPBACK}>

This has always perplexed me also, considering that the hose outlet nipple is above the sealing surface of the radiator cap. It is easy enough to fugure out how the overheating water from the radiator gets into the tank, since the radiator cap is spring loaded and will open at 15 psi or whatever. Defies logic as to how the cold water gets back into the radiator as the radiator cap pressing shut would prevent this. There is no process of physics that makes sense to me, IE siphon action,etc. Can anyone explain how the water gets from the tank into the radiator / cooling system?

Hence, I've never trusted the holding tank and always opened the radiator cap once in a while to look inside and ensure that the water level is above the cooling fins (When the engine is cold in the morning of course- never open hot). Certainly can't hurt to check and doesn't take but a few more seconds of time.

<{POST_SNAPBACK}>

I always thought that the hose from the radiator was connected below the cap seal but unfortunately I can't run out and check because the pickup is in the shop!!!

Where ever it hooks up I think the driving force to get the water back into the radiator is suction. If the water in the engine boils to expel the water then as the engine cools the steam will condense back to water and create a suction which will suck the water back in....I think....but this experience has shaken my confidence in my understanding of auto maintenence!!!

Also, it seems to me that original equipment radiator caps sometimes had a message on them that said not to open them to add coolant but to do it in the tank. Am I imagining this or do/did they say this?

[Thetyim]

The outlet to the expansion tank is below the sealing cap otherwise the rad would not pressurise.

If you look closely at your rad cap you will see that it has two valves.

The second valve lets the coolant back into the rad when under negative pressure.

[bino]

Reading this thread has made me curious and paranoid!

Paranoid- I just went downstairs to my car and checked the water - was OK.

Curious- to see how my tank is really connected / how it works.

The outlet to the expansion tank is below the sealing cap otherwise the rad would not pressurise.

If you look closely at your rad cap you will see that it has two valves.

The second valve lets the coolant back into the rad when under negative pressure.

Maybe there are various designs among cars, but mine (Mitsubishi Lancer) is as I described. There are two rubber seals in the radiator cap. One seals against the top edge of the radiator opening, and the other is on a spring loaded plunger that presses down into the base of the opening. The nipple is above the spring loaded plunger. I didn't see anything that resembled a second valve that would open under negative pressure.

If you think about it, the radiator tank would be unsafe to open hot if the outlet was below the sealing cap as the tank would also pressurize.

My tank is clearly not pressurized. The filler cap on the tank is a "press fit" item (like a shampoo bottle, but bigger) that pops open with slight finger pressure. It sure wouldn't withstand 15 PSI. In addition to the hose coming from the radiator there is also an overflow hose coming out of the tank leading down to the ground with no check / pressure valve on it.

I'm still perplexed.

Edited May 20, 2005 by bino

[Thetyim]

OK, Bino.

As you say design will vary, the expansion tank is not pressurised unless it is a volvo, VW or some citroens.

Have a look at the centre of your pressure cap. Mine has a small valve

which is not spring loaded, it is just like a one-way valve and is held in the closed position by the radiator pressure.

[ozzydom]

Reading this thread has made me curious and paranoid!

Paranoid- I just went downstairs to my car and checked the water - was OK.

Curious- to see how my tank is really connected / how it works.

The outlet to the expansion tank is below the sealing cap otherwise the rad would not pressurise.

If you look closely at your rad cap you will see that it has two valves.

The second valve lets the coolant back into the rad when under negative pressure.

<{POST_SNAPBACK}>

Maybe there are various designs among cars, but mine (Mitsubishi Lancer) is as I described. There are two rubber seals in the radiator cap. One seals against the top edge of the radiator opening, and the other is on a spring loaded plunger that presses down into the base of the opening. The nipple is above the spring loaded plunger. I didn't see anything that resembled a second valve that would open under negative pressure.

If you think about it, the radiator tank would be unsafe to open hot if the outlet was below the sealing cap as the tank would also pressurize.

My tank is clearly not pressurized. The filler cap on the tank is a "press fit" item (like a shampoo bottle, but bigger) that pops open with slight finger pressure. It sure wouldn't withstand 15 PSI. In addition to the hose coming from the radiator there is also an overflow hose coming out of the tank leading down to the ground with no check / pressure valve on it.

I'm still perplexed.

<{POST_SNAPBACK}>

you right bino, it is no more than a resevoir,remember when on a hot day you would see coolant running out the radiator tube ?well coolant has a few nasties in it so it was originally an environmental thing because it can be corrosive.there is no valve as such involved, just two sealing washers with a spigot exitting the radiator neck in between them,under pressure higher than the cap allows, coolant will escape and goes to the resevoir (which is why the bottle is onlly 1/2 full) then as engine and radiator cool a vacuum is created and sucks water back until there is no air space left to form the vacuum. easy huh.

[Thetyim]

Ozzy, sorry mate but you are wrong.

Tha cap contains TWO valves. A pressure valve and a vacuum valve.

[Thetyim]

Ozzy, sorry mate but you are wrong.

Tha cap contains TWO valves. A pressure valve and a vacuum valve.

[bino]

I'm still not getting it ozzy.....

you right bino, it is no more than a resevoir,remember when on a hot day you would see coolant running out the radiator tube ?well coolant has a few nasties in it so it was originally an environmental thing because it can be corrosive.

I can understand this - in addition to being corrosive, antifreeze it is highly poisonous and dangerous to animals who would go for the glycol (sugar) taste.

there is no valve as such involved, just two sealing washers with a spigot exitting the radiator neck in between them,under pressure higher than the cap allows, coolant will escape and goes to the resevoir (which is why the bottle is onlly 1/2 full)

Also understand this- I went back down to my car and looked at the rad cap- there is definitely no valve in the bottom of the spring loaded plunger. Can see how excess pressure would push the plunger up and allow the water out.

then as engine and radiator cool a vacuum is created and sucks water back until there is no air space left to form the vacuum. easy huh.

This is where I don't get it. Wouldn't a vacuum in the radiator only help to pull the seal on the plunger shut, aided by the spring, and block the water returning from the tank to the radiator?

What force of physics or mechanism overcomes the spring and opens the plunger to allow the water to return to the radiator?

I'm still perplexed.

[bino]

I stand corrected... after a third trip down to the carpark, I've finally got it straight.

Thetyim is correct- the metal center of the plunger is indeed a vacuum valve that I never noticed before. The big rivet in the center looked very solid and permanently attached to the plunger. Took a fair bit of finger pressure to get it open, but it opened.

Thanks for all the inputs! I'll sleep better tonight understanding this!

And- to address the initial question posted by chownah, it would appear that you are right to check from the tank. You may want to check your radiator cap to ensure that the vacuum valve is working and allowing coolant to replenish your radiator from the tank.

Edited May 20, 2005 by bino

[ozzydom]

Ozzy,  sorry mate but you are wrong.

Tha cap contains TWO valves. A pressure valve and a vacuum valve.

<{POST_SNAPBACK}>

your right of course thetyim,my mistake is not classing them as valves, but of course they are a simple valve, on most of the ones I worked on the expansion valve is simply pressure overcoming the spring rating and allowing the rubber seal to lift off its seat whereas the vacuum only has to overcome the low pressure compression spring and allow the centre spigot to come off its seat .

cheers mate if I knew how to work this computer I could draw one to show how simple they are .

[chownah]

Yeah you are all correct on the radiator outlet hose placement. I still can't go look at mine but you are right on in that the pressure would all leak out the hose if built the way I described.

Also, my pickup does not have the original equipment radiator cap....at least it looks like a cheap replacement. Is it possible that it does not have the proper valve arrangements to get the water sucked back in and therein lies my problem...the radiator cap lets the water exit and not enter so that over time the radiator will empty....since I think its all working fine I don't check the radiator itself and voila...disaster! I think I'll check out the cap too and see if its the right one.

Thanks everyone, I was a bit disheartened by this but now I feel like I have an understanding and a direction to go in to avoid this in the future.

Chownah

Edited May 20, 2005 by chownah

[bino]

Chownah,

I've go another thought for you regarding cooling systems... but not sure if it applies here in warm climates. I'm remembering a friend of mine at home who burned up his engine when a frost plug leaked out all of the coolant.

In the cold climates there are sacrificial plugs "press fit" into the engine block that are intended to give way if your coolant ever expands under freezing to prevent the block being cracked by the expansion.

Like I said- I'm not sure if they are used in tropical climates where there is no chance of freezing. I can't see any on my car, but they could be there under all of the exhaust header, intake manifold, alternator and all of the other attchments.

If you are having to pull the engine to repair it (imagine so), then you might want to inspect these and replace them.

Edited May 20, 2005 by bino

[chownah]

Chownah,

I've go another thought for you regarding cooling systems... but not sure if it applies here in warm climates. I'm remembering a friend of mine at home who burned up his engine when a frost plug leaked out all of the coolant.

In the cold climates there are sacrificial plugs "press fit" into the engine block that are intended to give way if your coolant ever expands under freezing to prevent the block being cracked by the expansion.

Like I said- I'm not sure if they are used in tropical climates where there is no chance of freezing. I can't see any on my car, but they could be there under all of the exhaust header, intake manifold, alternator and all of the other attchments.

If you are having to pull the engine to repair it (imagine so), then you might want to inspect these and replace them.

<{POST_SNAPBACK}>

Good advice. I've told the mechanic to check out everything and fix whatever. Maybe I'll see if I can explain this to my wife and have her ask him. Getting this taken care of has been stressful for both of us...I rely on her to translate for me and she has no knowledge whatsoever of mechanics...she gets really stressed and I can really sympathize with her...I'm glad I've got a couple of good dictinaries to translate back and forth...we use them alot.

[bino]

Getting this taken care of has been stressful for both of us...I rely on her to translate for me and she has no knowledge whatsoever of mechanics...she gets really stressed and I can really sympathize with her...I'm glad I've got a couple of good dictinaries to translate back and forth...we use them alot.

Can sympathize with you 100% mate- I'm sure the ThaiSoftware computer dictionary has helped the relationship with my GF many times!

We go through this every time we go to the auto mechanic or computer store! While my GF knows how to "drive" both of them- she doesn't know (or care) much about the workings, which I am enthusiastic / obsessive about. The whole experience usually ends up costing an expensive dinner on top of the repair bill!

Like Willie Nelson sings- I hope you are "On the road again" soon.

Edited May 20, 2005 by bino

[Thetyim]

Chownah, I have the same problem and being an engineer by trade I often get into disagreements with Thai engineers who vary from being mechanically unconcious to first rate.

I bought myself a Thai/English engineers dictionary and I find it very useful when getting the pick-up serviced.

Thais for some reason seem to think that the fan belt should be greased. I have had three arguments in three "service stations" about this. Not only do they disagree with me but insist on carrying on and greasing it for me. Why can't the customer have want he wants ? Needless to say the wife gets caught in the middle and we end up not speaking for a day, just because some halfwit mechanic doesn't know his job.

[bino]

I bought myself a Thai/English engineers dictionary and I find it very useful when getting the pick-up serviced.

This sounds like a definitely good idea! I'd like to have one also. What is it called, and where did you get it?

[Thetyim]

Well on the outside hardback cover it is called

"Engineering's Dictionary English-Thai"

and inside it is called "Electric Science and Mechanical Dictionary"

Anyway look out for a green 650 pages hardback book,

150 Baht from DK Books. No ISBN number.

FYI Saipan mai tong sai julabi. Hai dai.

Don't put grease on the fanbelts or I'll kill you

[billd766]

I had an overheating problem with my wifes old Nissan Sunny and it warped the cylinder head slightly and caused evn more problems as exhast gases got into the water jacket around the engine and pumped cooling water out causing the engine to overheat.

After 5 visits to the Nissan dealer on Sukhumvit I took the car to a small mechanics shop around the corner who identified the problem in 20 minutes and fixed it in less than a day. They also told me I needed a new radiator as mine was sludged up. They replaced that and touch wood there have been no more overheating problems.