What does high oil temp tell you?
10-09-2011, 09:22 PM
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What does high oil temp tell you? Recently spun a bearing in my stock LS1-powered Miata. Coolant temps were normal, but I'd noticed the oil temps trending upward and recovering more slowly after an autocross run (I'm running a 48K btu oil cooler) than normal.
Question: how would you interpret either higher-than normal oil temps (as related to coolant temps) or slower recovery than normal?
TIA, and have a good one,
Mike
Question: how would you interpret either higher-than normal oil temps (as related to coolant temps) or slower recovery than normal?
TIA, and have a good one,
Mike
10-09-2011, 09:31 PM
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I think I think you have already diagnosed the problem if you say that you have spun a bearing. Generally from my experience a spun bearing will cause higher than normal oil temps and lower oil pressure. Not 100% sure on that Im sure someone else will chime in if I am wrong. Any blow by when you pull the oil cap?
10-10-2011, 06:44 AM
#3
Recently spun a bearing in my stock LS1-powered Miata. Coolant temps were normal, but I'd noticed the oil temps trending upward and recovering more slowly after an autocross run (I'm running a 48K btu oil cooler) than normal.
Question: how would you interpret either higher-than normal oil temps (as related to coolant temps) or slower recovery than normal?
TIA, and have a good one,
Mike
Question: how would you interpret either higher-than normal oil temps (as related to coolant temps) or slower recovery than normal?
TIA, and have a good one,
Mike
Specifically, what are you considering higher than normal & slower than normal? An autocross run may spike the oil temp simply from the high revs...That's absolutely normal. If you spun the bearing auto-crossing, it is most likely from hard cornering having caused temporary oil starvation. A pre-oiler is always a good idea & will help to protect the engine from oil starvation.
To answer the question, "does a spun bearing cause higher than normal oil temps?" Under high performance driving conditions, like auto-cross, possibly. Would depend on whether or not the bearing had started walking sideways out of the rod. If it has, then the increase in friction would heat the oil more quickly. Same could be said if the bearing had disintegrated to the point where the rod was rubbing against the crank.
EDIT:
FYI & for reference, on a road course, it is possible for the oil temps can reach 280*+F, all the while showing near normal coolant temps.
Last edited by LS1-450; 10-10-2011 at 06:52 AM. Reason: Added, FYI
10-10-2011, 07:46 AM
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Sorry folks, I guess I wasn't clear.
I understand that a spun bearing can cause high oil temps, but isn't that the end-game? My question was intended to be "when you see higher than normal oil temps (I'll detail that in a minute) what can you interpret from that?"
Now, to higher than normal oil temps. First off, note again I'm running a 48k BTU external oil cooler. Running the same system on my '00 C5 I see oil temps on the road around 185-190, coolant temps around 200 at steady-state highway speeds. Same scenario, in my Miata I'm seeing coolant temps around 200, BUT oil temps around 210 or so. Been like that more or less since day 1 after the Miata install.
In my C5 during autocrosses I've seen spikes up to 275 due to high power and low speeds (i.e. not much airflow). In DE conditions oil temps are usually in the low 260s, and that's running her hard. When I started a cooldown lap I'll see a drop down into the 220s by the time I come off track. Cooling down after 4 autocross runs (oil temps in the 270s) they'll drop down into the 240s on a 1 mile coast out.
In the Miata on a DE I was having to monitor oil temps to keep them from climbing above 250; not too bad but still higher than I was expecting considering my previous experience with my C5. On the autocross I was watering down my oil cooler to try to get the temps down, and it just took a lot of effort to get much response.
This is my first experience with a spun bearing. The bearing is a mess, actually extruding and flowing out between the rod and the crank. Crank is damaged, don't know if it can be repaired or not. Thanks for the ideas about the bearing walking, etc.
Y'all have a good one,
Mike
I understand that a spun bearing can cause high oil temps, but isn't that the end-game? My question was intended to be "when you see higher than normal oil temps (I'll detail that in a minute) what can you interpret from that?"
Now, to higher than normal oil temps. First off, note again I'm running a 48k BTU external oil cooler. Running the same system on my '00 C5 I see oil temps on the road around 185-190, coolant temps around 200 at steady-state highway speeds. Same scenario, in my Miata I'm seeing coolant temps around 200, BUT oil temps around 210 or so. Been like that more or less since day 1 after the Miata install.
In my C5 during autocrosses I've seen spikes up to 275 due to high power and low speeds (i.e. not much airflow). In DE conditions oil temps are usually in the low 260s, and that's running her hard. When I started a cooldown lap I'll see a drop down into the 220s by the time I come off track. Cooling down after 4 autocross runs (oil temps in the 270s) they'll drop down into the 240s on a 1 mile coast out.
In the Miata on a DE I was having to monitor oil temps to keep them from climbing above 250; not too bad but still higher than I was expecting considering my previous experience with my C5. On the autocross I was watering down my oil cooler to try to get the temps down, and it just took a lot of effort to get much response.
This is my first experience with a spun bearing. The bearing is a mess, actually extruding and flowing out between the rod and the crank. Crank is damaged, don't know if it can be repaired or not. Thanks for the ideas about the bearing walking, etc.
Y'all have a good one,
Mike
10-10-2011, 08:18 AM
#5
Sorry folks, I guess I wasn't clear.
I understand that a spun bearing can cause high oil temps, but isn't that the end-game? My question was intended to be "when you see higher than normal oil temps (I'll detail that in a minute) what can you interpret from that?"
Now, to higher than normal oil temps. First off, note again I'm running a 48k BTU external oil cooler. Running the same system on my '00 C5 I see oil temps on the road around 185-190, coolant temps around 200 at steady-state highway speeds. Same scenario, in my Miata I'm seeing coolant temps around 200, BUT oil temps around 210 or so. Been like that more or less since day 1 after the Miata install.
In my C5 during autocrosses I've seen spikes up to 275 due to high power and low speeds (i.e. not much airflow). In DE conditions oil temps are usually in the low 260s, and that's running her hard. When I started a cooldown lap I'll see a drop down into the 220s by the time I come off track. Cooling down after 4 autocross runs (oil temps in the 270s) they'll drop down into the 240s on a 1 mile coast out.
In the Miata on a DE I was having to monitor oil temps to keep them from climbing above 250; not too bad but still higher than I was expecting considering my previous experience with my C5. On the autocross I was watering down my oil cooler to try to get the temps down, and it just took a lot of effort to get much response.
This is my first experience with a spun bearing. The bearing is a mess, actually extruding and flowing out between the rod and the crank. Crank is damaged, don't know if it can be repaired or not. Thanks for the ideas about the bearing walking, etc.
I understand that a spun bearing can cause high oil temps, but isn't that the end-game? My question was intended to be "when you see higher than normal oil temps (I'll detail that in a minute) what can you interpret from that?"
Now, to higher than normal oil temps. First off, note again I'm running a 48k BTU external oil cooler. Running the same system on my '00 C5 I see oil temps on the road around 185-190, coolant temps around 200 at steady-state highway speeds. Same scenario, in my Miata I'm seeing coolant temps around 200, BUT oil temps around 210 or so. Been like that more or less since day 1 after the Miata install.
In my C5 during autocrosses I've seen spikes up to 275 due to high power and low speeds (i.e. not much airflow). In DE conditions oil temps are usually in the low 260s, and that's running her hard. When I started a cooldown lap I'll see a drop down into the 220s by the time I come off track. Cooling down after 4 autocross runs (oil temps in the 270s) they'll drop down into the 240s on a 1 mile coast out.
In the Miata on a DE I was having to monitor oil temps to keep them from climbing above 250; not too bad but still higher than I was expecting considering my previous experience with my C5. On the autocross I was watering down my oil cooler to try to get the temps down, and it just took a lot of effort to get much response.
This is my first experience with a spun bearing. The bearing is a mess, actually extruding and flowing out between the rod and the crank. Crank is damaged, don't know if it can be repaired or not. Thanks for the ideas about the bearing walking, etc.
Oil temperatures of 275 F is normal at the track.
Last edited by Darkman; 10-10-2011 at 08:50 AM. Reason: spelling
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10-11-2011, 07:39 AM
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Darkman,
Stock C5 oil temps run in the low 200s; the oil doesn't need to get to the boiling point to dry the water out, but it does need to get to about 180 or so to "get ahead" of the water vapor being added to the crankcase via combustion blowby. BTW, my C5 engine oil cooler *did* have a t'stat in the oil cooling loop. I didn't put that into my Miata, hoping to get a bit better oil cooling in a car destined to see more track time.
Instead I always saw higher than expected oil temps.
LS1-450, I sure hope your last comment wasn't directed towards me. I know some, but never too much. This is my first experience with a spun bearing in an engine I own and use, and I'm mainly wondering if there was something I could have seen that I need to watch for in the future to minimize damage to the engine.
BTW, what's the story on your Munster? Sounds like we may be brethren!
Have a good one,
Mike
Stock C5 oil temps run in the low 200s; the oil doesn't need to get to the boiling point to dry the water out, but it does need to get to about 180 or so to "get ahead" of the water vapor being added to the crankcase via combustion blowby. BTW, my C5 engine oil cooler *did* have a t'stat in the oil cooling loop. I didn't put that into my Miata, hoping to get a bit better oil cooling in a car destined to see more track time.
Instead I always saw higher than expected oil temps.
LS1-450, I sure hope your last comment wasn't directed towards me. I know some, but never too much. This is my first experience with a spun bearing in an engine I own and use, and I'm mainly wondering if there was something I could have seen that I need to watch for in the future to minimize damage to the engine.
BTW, what's the story on your Munster? Sounds like we may be brethren!
Have a good one,
Mike
Last edited by Vettedrmr; 10-11-2011 at 07:40 AM. Reason: Added BTW
10-11-2011, 07:59 AM
#9
High oil temps are not good for a lot of reasons but you are probably chasing ghosts if you think that is why your bearing spun. Lack of oil, clearance or dimensional problems, wear, Good consistent oil pressure and proper clearances keeping the metal parts away from each other is what keeps bearings from spinning.
10-11-2011, 08:48 AM
#10
Darkman,
Stock C5 oil temps run in the low 200s; the oil doesn't need to get to the boiling point to dry the water out, but it does need to get to about 180 or so to "get ahead" of the water vapor being added to the crankcase via combustion blowby. BTW, my C5 engine oil cooler *did* have a t'stat in the oil cooling loop. I didn't put that into my Miata, hoping to get a bit better oil cooling in a car destined to see more track time.
Instead I always saw higher than expected oil temps.
Stock C5 oil temps run in the low 200s; the oil doesn't need to get to the boiling point to dry the water out, but it does need to get to about 180 or so to "get ahead" of the water vapor being added to the crankcase via combustion blowby. BTW, my C5 engine oil cooler *did* have a t'stat in the oil cooling loop. I didn't put that into my Miata, hoping to get a bit better oil cooling in a car destined to see more track time.
Instead I always saw higher than expected oil temps.
10-12-2011, 07:37 AM
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High oil temps are not good for a lot of reasons but you are probably chasing ghosts if you think that is why your bearing spun. Lack of oil, clearance or dimensional problems, wear, Good consistent oil pressure and proper clearances keeping the metal parts away from each other is what keeps bearings from spinning.
Thanks for replying. I think you're right; I'm probably wasting my time trying to figure out what I could have done differently. The only thing I can think of is I didn't get enough clearance between the oil pickup tube and the bottom of my custom oil pan (stock pans won't work on a Miata conversion). I didn't learn until painfully after the fact that I need about 1/4" between the pickup and the bottom of the pan. I haven't measured it but I'm guessing it's quite a bit closer than that.
Darkman, it's all good. Strangely enough, I've found that gearheads can disagree about a lot of things and we all still do pretty good!
Thanks again for the responses, and have a good one,
Mike
