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Question: Oil and coolant temps 1986 C4

Mojoman

New member
Joined
Oct 28, 2015
Messages
2
Location
Louisiana
Hi, I'm new to this forum and also as a Vette owner. I have a black 1986 C4 with 29,000 original miles. Got the Vette from the original purchaser who garage kept it from day one - neighbor. Anyway, the car had NOT been driven for the last 6 - 7 years, or for that matter even started. After replacing all fluids, ('mopped' out the gas tank), separate heater core and motor coolant flush, plugs, battery, fuel pump, thankfully only rocker cover gaskets, and a few other small repairs, I have two questions. First, what is the normal or should I say range for the oil temp in this vehicle while driving and also at idle? Second, I know these Vettes were designed to be driven with fairly high coolant temps before the fans kick in, (unless a/c is operating), and my question is, has anyone taken it upon themselves to
run their Vettes with lower coolant temps, (190 - 200 range) and have any issues developed because of lowering your coolant operating temp? Sorry to get a little winded, but wanted to give you a rough idea of the vehicle. BTW, my coolant temps are right where Chevy designed them to be, fan kicks in around 227, and my oil temp running is in the neighborhood of 200 driving and around 220 after driving and letting it idle for a few minutes. Thanks in advance for any responses.
 

LLC5

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Joined
Sep 28, 2004
Messages
2,299
Location
Wa.
Corvette
98 black 6spd convert.
Your numbers are fine. Why would you want to lower the normal running coolant temps from OEM spec's?
 

Mojoman

New member
Joined
Oct 28, 2015
Messages
2
Location
Louisiana
Your numbers are fine. Why would you want to lower the normal running coolant temps from OEM spec's?

Mainly, I wanted to know the oil temp was within limits and I didn't have a blockage, circulation, or oil pump malfunction. (if you could have seen what came out of the gas tank & the heater core and engine flush!!). As for lowering the coolant temp, cooler engine, longer life? It has only been in the high 70's here lately, Louisiana, and I was wandering what it was gonna be like when we are back over 100 next year. :) Thanks LLC5.
 

LLC5

Well-known member
Joined
Sep 28, 2004
Messages
2,299
Location
Wa.
Corvette
98 black 6spd convert.
Mainly, I wanted to know the oil temp was within limits and I didn't have a blockage, circulation, or oil pump malfunction. (if you could have seen what came out of the gas tank & the heater core and engine flush!!). As for lowering the coolant temp, cooler engine, longer life? It has only been in the high 70's here lately, Louisiana, and I was wandering what it was gonna be like when we are back over 100 next year. :) Thanks LLC5.



Your good to go. As Vettehead Mikey said keep it stock.

What you can do to insure that the coolant stays in range is make sure that there is no debris blocking the cooling fins in the radiator and condenser, I actually have a tool that forces compressed air or water between the fins to get out a lot of small debris that IS in there (even if you cannot see them) safely.
 

DonB

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Joined
Mar 25, 2015
Messages
339
Location
Chicago
Corvette
2019 ZO6 in Elkhart Lake Blue
Hi, I'm new to this forum and also as a Vette owner. I have a black 1986 C4 with 29,000 original miles. Got the Vette from the original purchaser who garage kept it from day one - neighbor. Anyway, the car had NOT been driven for the last 6 - 7 years, or for that matter even started. After replacing all fluids, ('mopped' out the gas tank), separate heater core and motor coolant flush, plugs, battery, fuel pump, thankfully only rocker cover gaskets, and a few other small repairs, I have two questions. First, what is the normal or should I say range for the oil temp in this vehicle while driving and also at idle? Second, I know these Vettes were designed to be driven with fairly high coolant temps before the fans kick in, (unless a/c is operating), and my question is, has anyone taken it upon themselves to
run their Vettes with lower coolant temps, (190 - 200 range) and have any issues developed because of lowering your coolant operating temp? Sorry to get a little winded, but wanted to give you a rough idea of the vehicle. BTW, my coolant temps are right where Chevy designed them to be, fan kicks in around 227, and my oil temp running is in the neighborhood of 200 driving and around 220 after driving and letting it idle for a few minutes. Thanks in advance for any responses.

Everyone here that has replied so far will probably dispute what I'm going to say,.....BUT!

Last year I bought a base '90w/auto that had over 200k on it. This past 9 months I've rebuilt the whole drive-train, front end, brakes, electrical, interior and just about everything else. She's still close to stock.
The engine was blueprinted by my machinist and me. At 61 years young(and a former gearhead and dealer mechanic), I relished the opportunity. I hadn't done this "in years."
I quickly noticed the engine ran at very high temperature. Normally according to the FSM.

You are correct. The fan is supposed to come on at about 227*....it's actually 229* Sit in traffic and the temp can go up to 260 rapidly, especially on a hot, muggy day. Even with a good radiator. That is INSANE for aluminum heads on a cast iron block. There is a FIX for that.

Search on the site for C4 coolant temp. There is a kit make for Corvette Central that has the fans come on at about 195* It keeps the engine very happy. Powerful and Cool. It's easily installed and costs about 40 bucks. Plus you won't warp heads and blow head gaskets.
I'd recommend a 160* thermostat too.

(I know I'll get my head bit off for that comment.)


Should you need more help.....let me know. Shoot me a PM
 

Vettehead Mikey

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Joined
Aug 26, 2003
Messages
3,486
Location
Not that far from Ottawa
Corvette
1973 Coupe
If the thermostat and fans won't keep an engine within the desired temp range, that specific problem must be fixed. Attempting to lower the desired temp range to address that makes no sense.
 

DonB

Well-known member
Joined
Mar 25, 2015
Messages
339
Location
Chicago
Corvette
2019 ZO6 in Elkhart Lake Blue
My point WAS NOT to circumvent the cooling system because of a malfunction.
My point Mikey was that I feel the operating temperatures are excessive. You keep running those aluminum heads at high Temps and you'll warp those heads like a cheap piece of plywood. Plus you will need to constantly torque the head bolts to avoid blowing head gaskets.

What the OP asked is a well documented issue with these engines, whether the "purists" believe it or not.
You run yours as you wish. I 'll keep mine nice and cool at 185.

Google Luck.
 

Vettehead Mikey

Well-known member
Joined
Aug 26, 2003
Messages
3,486
Location
Not that far from Ottawa
Corvette
1973 Coupe
My point WAS NOT to circumvent the cooling system because of a malfunction.
My point Mikey was that I feel the operating temperatures are excessive. You keep running those aluminum heads at high Temps and you'll warp those heads like a cheap piece of plywood. Plus you will need to constantly torque the head bolts to avoid blowing head gaskets.

What the OP asked is a well documented issue with these engines, whether the "purists" believe it or not.
You run yours as you wish. I 'll keep mine nice and cool at 185.

Google Luck.

Just for fun, let's say that reaching 260*F coolant temp was a typical occurrence on these engines. If what you say was true- why aren't the roads littered with dead Corvettes?

The OP made no mention of his engine reaching 260*. Is it not more likely that there's something wrong with your Corvette and you've put a band-aid fix on it?

Google luck to you too. :D
 

buford87

Member
Joined
Jul 3, 2014
Messages
11
Location
NW,Pa
Corvette
1987 Coupe Bright red 4+3
Cooler is better

Everyone here that has replied so far will probably dispute what I'm going to say,.....BUT!

Last year I bought a base '90w/auto that had over 200k on it. This past 9 months I've rebuilt the whole drive-train, front end, brakes, electrical, interior and just about everything else. She's still close to stock.
The engine was blueprinted by my machinist and me. At 61 years young(and a former gearhead and dealer mechanic), I relished the opportunity. I hadn't done this "in years."
I quickly noticed the engine ran at very high temperature. Normally according to the FSM.

You are correct. The fan is supposed to come on at about 227*....it's actually 229* Sit in traffic and the temp can go up to 260 rapidly, especially on a hot, muggy day. Even with a good radiator. That is INSANE for aluminum heads on a cast iron block. There is a FIX for that.

Search on the site for C4 coolant temp. There is a kit make for Corvette Central that has the fans come on at about 195* It keeps the engine very happy. Powerful and Cool. It's easily installed and costs about 40 bucks. Plus you won't warp heads and blow head gaskets.
I'd recommend a 160* thermostat too.

(I know I'll get my head bit off for that comment.)


Should you need more help.....let me know. Shoot me a PM




I've built small block chevys for years (I'm 68) I agree with you on lowering the temp. I installed a 160 thermostat and a fan switch that comes on at 192 off at 180. I also wired mine so both fans come on together. Manual trans C4s have an aux fan ahead of the radiator. They can chew on me all they want but I've built some really fast chevys. And I've had good continuous performance from them with a lower temp. Nascar runs higher temp for several reason none of them for engine longevity usually under 600 miles.
 

DonB

Well-known member
Joined
Mar 25, 2015
Messages
339
Location
Chicago
Corvette
2019 ZO6 in Elkhart Lake Blue
I've built small block chevys for years (I'm 68) I agree with you on lowering the temp. I installed a 160 thermostat and a fan switch that comes on at 192 off at 180. I also wired mine so both fans come on together. Manual trans C4s have an aux fan ahead of the radiator. They can chew on me all they want but I've built some really fast chevys. And I've had good continuous performance from them with a lower temp. Nascar runs higher temp for several reason none of them for engine longevity usually under 600 miles.


Thanks Buford87. I'm glad some one understands....I'm probably using the same set-up as you and "she's" always happy! Continuous Performance is the key. APPLES & ORANGES here, but... I have 2, 350 - 320/h/p in my boat and she runs at 175* all day long. Never had "any" performance" issues caused by temperature and they are "haulin' the mail!", when they are running(just like the Vette)... I also use a minimum of Castrol 10w40 Synthetic. But that's another argument.
 

buford87

Member
Joined
Jul 3, 2014
Messages
11
Location
NW,Pa
Corvette
1987 Coupe Bright red 4+3
Oil wieght

Thanks Buford87. I'm glad some one understands....I'm probably using the same set-up as you and "she's" always happy! Continuous Performance is the key. APPLES & ORANGES here, but... I have 2, 350 - 320/h/p in my boat and she runs at 175* all day long. Never had "any" performance" issues caused by temperature and they are "haulin' the mail!", when they are running(just like the Vette)... I also use a minimum of Castrol 10w40 Synthetic. But that's another argument.



I run 10w 40 Mobile 1 and have for years in everything I drive. No oil related issues or breakdowns. My daily driver has 90,000 mi and I change oil at 4500 mi and never have to add in between.
 

DonB

Well-known member
Joined
Mar 25, 2015
Messages
339
Location
Chicago
Corvette
2019 ZO6 in Elkhart Lake Blue
Yes,.. It CAN be a beautiful thing!
 

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