# High oil temperature, normal oil pressure in Chevy S10



## farmerjohn1324 (Jul 28, 2015)

I have a 2002 Chevy s10. The oil temperature says it's high, the oil pressure is normal. What should I check first? And do I need to let the engine cool down before checking?


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## farmerjohn1324 (Jul 28, 2015)

Seemed like it was low on coolant so I added some. How long should I drive it for before thinking it might be something else if the gauge doesn't go down to normal temperature?


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## chandler48 (Jun 5, 2017)

The S10 actually has an oil temperature gauge?? Oil cools the engine.....water cools the oil. Make sure you have "burped" the water system behind the thermostat housing if it is equipped with a 1/4" plug there. Otherwise, you will have an air embolism in the system.


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## farmerjohn1324 (Jul 28, 2015)

chandler48 said:


> The S10 actually has an oil temperature gauge?? Oil cools the engine.....water cools the oil. Make sure you have "burped" the water system behind the thermostat housing if it is equipped with a 1/4" plug there. Otherwise, you will have an air embolism in the system.


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## chandler48 (Jun 5, 2017)

That's not al OIL temperature gauge. It is your coolant temperature gauge and you are overheating. Fill the radiator and see if the temperature goes down.


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## farmerjohn1324 (Jul 28, 2015)

chandler48 said:


> That's not al OIL temperature gauge. It is your coolant temperature gauge and you are overheating. Fill the radiator and see if the temperature goes down.


I filled it from the reservoir. Is that just as good as filling from the radiator? It was low and looked dirty.


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## chandler48 (Jun 5, 2017)

No it isn't. The reservoir only sucks water back into the radiator once it starts cooling. Pop the radiator cap once it is cooled and add coolant mixture 50:50. Start the engine and bring it to operating temperature with the lid off. Once the thermostat opens the water in the radiator will go down substantially. Then fill it up completely and return the cap.


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## huesmann (Aug 18, 2011)

Let's hope you don't need a new head gasket...


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## farmerjohn1324 (Jul 28, 2015)

huesmann said:


> Let's hope you don't need a new head gasket...


Do you know how I could determine this? Or should I just replace the coolant and hope for the best? And take it in to a professional if a coolant flush doesn't help.


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## iamrfixit (Jan 30, 2011)

First get some coolant in it. Let the engine cool down completely. Open the radiator cap and fill up the radiator. Run the engine with the cap off until the thermostat opens and the upper radiator hose gets hot. This should purge the air out on most vehicles. Top off the radiator and install the cap, then fill the overflow up to the hot line. Closely monitor the level in the overflow tank, if it's continually going low then that means the engine is either leaking or consuming coolant. The coolant will shrink as it cools and pull coolant from the tank, as the engine heats up it will push excess coolant back to the overflow tank. The tank should stay between the cold and hot lines.

Make it a habit each time you park the vehicle look around under it as you leave and when you return. Look for coolant dripping or leaking and look for any puddles. Don't mistake coolant for the AC condensate that drips off, usually under the passenger side behind the front tire. 

Most likely it's coolant leaking somewhere, but if you allow the vehicle to continually run run low, you WILL need major engine work soon enough. Engines do not consume coolant if they're healthy. If you see white smoke from the exhaust or seem to have a recurring miss when you start the vehicle on top of losing coolant, then you have a problem.


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## farmerjohn1324 (Jul 28, 2015)

iamrfixit said:


> First get some coolant in it. Let the engine cool down completely. Open the radiator cap and fill up the radiator. Run the engine with the cap off until the thermostat opens and the upper radiator hose gets hot. This should purge the air out on most vehicles. Top off the radiator and install the cap, then fill the overflow up to the hot line. Closely monitor the level in the overflow tank, if it's continually going low then that means the engine is either leaking or consuming coolant. The coolant will shrink as it cools and pull coolant from the tank, as the engine heats up it will push excess coolant back to the overflow tank. The tank should stay between the cold and hot lines.
> 
> Make it a habit each time you park the vehicle look around under it as you leave and when you return. Look for coolant dripping or leaking and look for any puddles. Don't mistake coolant for the AC condensate that drips off, usually under the passenger side behind the front tire.
> 
> Most likely it's coolant leaking somewhere, but if you allow the vehicle to continually run run low, you WILL need major engine work soon enough. Engines do not consume coolant if they're healthy. If you see white smoke from the exhaust or seem to have a recurring miss when you start the vehicle on top of losing coolant, then you have a problem.


How do I know when the thermostat opens?


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## chandler48 (Jun 5, 2017)

The top hose will get hot and the water in the radiator will suck down, displacing air in the engine.


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## farmerjohn1324 (Jul 28, 2015)

I just poured over a gallon of coolant in the radiator and it's still not to the top. What do you think? Should I try it now, or wait till I can get some more coolant tomorrow?

Google tells me this radiator has a 3 gallon capacity.


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## farmerjohn1324 (Jul 28, 2015)

farmerjohn1324 said:


> I just poured over a gallon of coolant in the radiator and it's still not to the top. What do you think? Should I try it now, or wait till I can get some more coolant tomorrow?


There was a small drip on the bottom that is coolant and not condensation. However, it stopped after only a little bit dripped so I think this is just a little bit that spilled when I missed with the funnel. 

That is a good sign, except that it doesn't tell me what the cause is. What could be a cause of low coolant if there's no leak?


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## iamrfixit (Jan 30, 2011)

Won't do you very much good if coolant is not pretty close to full capacity. 

The coolant system becomes under pressure when the engine is hot, so while it may not leak now, it could start after the engine warms up and the cooling system builds pressure. You often need to pressure check the cooling system to diagnose a small leak.

Something as simple as a bad radiator cap can allow coolant to continually escape as wisps of steam instead of being condensed back into the overflow tank. A leaking intake manifold, head gasket or a cracked head or block would be worst case scenario. These can all draw coolant into the combustion chamber and burn it. Some vehicles have water pumps that are internal, driven by the timing chain. These can leak coolant into the oil and quickly destroy the engine. Running low coolant or overheating can just as seriously damage or destroy the engine. Some engines can somewhat protect themselves while others very easily become damaged.


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## neil86 (Oct 13, 2018)

Which engine, 2.2 or 4.3? Agreed with those above, get that cooling system filled first then we can go from there if it continues. A bad radiator cap can cause issues, and they are cheap to replace, I have had good luck with Stant. Pull the dipstick and check the oil, make sure it doesn't look like a milkshake. I run an s10 now and have had several over the years.


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## farmerjohn1324 (Jul 28, 2015)

neil86 said:


> Which engine, 2.2 or 4.3? Agreed with those above, get that cooling system filled first then we can go from there if it continues. A bad radiator cap can cause issues, and they are cheap to replace, I have had good luck with Stant. Pull the dipstick and check the oil, make sure it doesn't look like a milkshake. I run an s10 now and have had several over the years.


4.3


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## farmerjohn1324 (Jul 28, 2015)

iamrfixit said:


> First get some coolant in it. Let the engine cool down completely. Open the radiator cap and fill up the radiator. Run the engine with the cap off until the thermostat opens and the upper radiator hose gets hot. This should purge the air out on most vehicles. Top off the radiator and install the cap, then fill the overflow up to the hot line. Closely monitor the level in the overflow tank, if it's continually going low then that means the engine is either leaking or consuming coolant. The coolant will shrink as it cools and pull coolant from the tank, as the engine heats up it will push excess coolant back to the overflow tank. The tank should stay between the cold and hot lines.
> 
> Make it a habit each time you park the vehicle look around under it as you leave and when you return. Look for coolant dripping or leaking and look for any puddles. Don't mistake coolant for the AC condensate that drips off, usually under the passenger side behind the front tire.
> 
> Most likely it's coolant leaking somewhere, but if you allow the vehicle to continually run run low, you WILL need major engine work soon enough. Engines do not consume coolant if they're healthy. If you see white smoke from the exhaust or seem to have a recurring miss when you start the vehicle on top of losing coolant, then you have a problem.


After starting it, you want me to top off the radiator with the engine running?

The reservoir isn't transparent enough for me to see the level without opening it, even after I clean the dirt off.


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## farmerjohn1324 (Jul 28, 2015)

After topping off the radiator and running the engine for about 20 minutes, the coolant temperature was normal. The alternator was hot to the touch and so was one of the hoses coming out of the radiator so I assume that means the engine got hot enough. There was definitely some coolant underneath but I spilled so much pouring it in, that I can't be sure if there were any leaks or not. I didn't add any more after it got hot, I will worry about it again tomorrow.


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## HotRodx10 (Aug 24, 2017)

Make sure to check the oil, as neil86 said, right away. If the coolant is getting into the oil, it will make the oil into sludge that won't circulate. If it gets to that point, the engine will be toast in minutes after that. If it looks milky or the level is high, you have a serious problem that you need to solve before attempting to run the engine.


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## farmerjohn1324 (Jul 28, 2015)

HotRodx10 said:


> Make sure to check the oil, as neil86 said, right away. If the coolant is getting into the oil, it will make the oil into sludge that won't circulate. If it gets to that point, the engine will be toast in minutes after that. If it looks milky or the level is high, you have a serious problem that you need to solve before attempting to run the engine.


The oil is definitely dark, but I don't know if it is mixed with coolant.

I'm fairly certain that I have a coolant leak because it's still dripping and I doubt it's just from what I missed with the funnel. 95% certain it's a leak.


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## farmerjohn1324 (Jul 28, 2015)

farmerjohn1324 said:


> The oil is definitely dark, but I don't know if it is mixed with coolant.
> 
> I'm fairly certain that I have a coolant leak because it's still dripping and I doubt it's just from what I missed with the funnel. 95% certain it's a leak.


After doing some Google searching... This does not look like I have coolant in the oil. So I probably just have a leak somewhere.


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## huesmann (Aug 18, 2011)

That oil looks OK. If it had coolant it'd be like chocolate milk. But you do look low.


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## farmerjohn1324 (Jul 28, 2015)

huesmann said:


> That oil looks OK. If it had coolant it'd be like chocolate milk. But you do look low.


So I probably have a coolant leak, but the head gasket is fine.


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## neil86 (Oct 13, 2018)

Can you move the truck to a dry spot? Let it run and get to temp and look for leaks. 

Cracks in radiator, check hoses and connections, water pump (should have a weep hole at the bottom, look there and all around WP), thermostat housing, heater core (is passenger floor wet?), I have also replaced several intake manifold gaskets that failed and caused an external leak of coolant.


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## HotRodx10 (Aug 24, 2017)

If you're not seeing coolant on the ground where you park it, my best guesses are either a radiator cap that is not holding the pressure it's supposed to (fairly common), or the seal around the water pump shaft is leaking. It's usually hard to get a look at, but there's a weep hole somewhere around the bottom water pump housing; if that's where the coolant is coming from. It will typically only leak while the engine is running and the coolant is under pressure (when it's up to temp with the radiator cap on). If the water pump seal is leaking, it's typically because the shaft bearing is worn out, which means the water pump will need to be replaced.


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## Old Thomas (Nov 28, 2019)

I owned several S10s, both trucks and Blazers. Almost every one needed its radiator replaced as it aged. Now they are even older. Most of the radiators can be purchased for a little over $100. Look carefully for radiator leaks. On my 93 it was especially hard to find the leak. It wept coolant and the heater would stop working. Then I filled the system and it worked again. It never left a puddle.


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## farmerjohn1324 (Jul 28, 2015)

HotRodx10 said:


> If you're not seeing coolant on the ground where you park it, my best guesses are either a radiator cap that is not holding the pressure it's supposed to (fairly common), or the seal around the water pump shaft is leaking. It's usually hard to get a look at, but there's a weep hole somewhere around the bottom water pump housing; if that's where the coolant is coming from. It will typically only leak while the engine is running and the coolant is under pressure (when it's up to temp with the radiator cap on). If the water pump seal is leaking, it's typically because the shaft bearing is worn out, which means the water pump will need to be replaced.


There's coolant all over the ground. So I have a leak somewhere, but it's not getting into the oil. So I have to find and fix the leak or just continue to fill it up. Does that sound right?


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## Steve2444 (Sep 28, 2020)

farmerjohn1324 said:


> There's coolant all over the ground. So I have a leak somewhere, but it's not getting into the oil. So I have to find and fix the leak or just continue to fill it up. Does that sound right?


If you got coolant all over the ground, you need to find the leak and fix it. Just adding more is asking to get stranded and damage the engine.


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## farmerjohn1324 (Jul 28, 2015)

Steve2444 said:


> If you got coolant all over the ground, you need to find the leak and fix it. Just adding more is asking to get stranded and damage the engine.


I'm getting it towed to a shop for them to look.

At least I got to sound smart when I called them and told them I knew it wasn't a head gasket because it wasn't in the oil.


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## Thom Paine (Nov 24, 2021)

Check for head gasket leak: tool and instructions...
head gasket tester amazon











How to: head gasket test you tube vid Scotty Kilmer


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## huesmann (Aug 18, 2011)

Why not just buy (or rent for free from Autozone) a coolant pressure test kit? Once you pump it up it should show you pretty easily where you're leaking coolant from.


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