safe operating temp

[Walter F.]

I have been reading that with anti freeze you should never let your temp get over 220. On my 84 the cooling fan does not kick on till 216. At what temp does damage begin to take place on an engine ?

[Michael W.]

Re: safe operating temp

220 makes no sense. Modern cars run at that temp (and higher) all the time.

[Ed S.]

Re: safe operating temp

What does your operating manual or the shop manual say is a "normal" operating temperature for your particular engine? Fluid under pressure has a higher boiling point than pure water (212 F). For each pound of pressure I think the boiling point increases by 7 degrees. RE your cooling fan starting at 216, again - check the shop manual or another technical source to determine what is normal functionality.

Actually, the change in boiling point is not linear. It varies some, but as a general rule for every pound of pressure, the boiling point of a 50-50 coolant mix increases by about 3 degrees F. So, as a hypothetical example, if you have an 8psi radiator cap the coolant will not boil until it reaches 248 F. Other factors will cause it to vary, such as the composition of the coolant & the ratio of the coolant to H20, and of course the rating of the pressure cap.

[Walter F.]

Re: safe operating temp

The Chilton manual says 238 is when the fan is suppose to turn on. That sounds risky to me. My cars switch was replaced and the computer. But the computer as I understand it does not turn the fan on. The switch does. My fan goes on at 216 and that sounds to hot to me. My dash cluster is accurate as it was rebuilt less then 1,000 miles ago.The fan always came on at 216 since I owned the car.

[Duke W.]

Re: safe operating temp

I have been reading that with anti freeze you should never let your temp get over 220.

Where have you been reading that?

Duke

[Michael W.]

Re: safe operating temp

The Chilton manual says 238 is when the fan is suppose to turn on.

That's correct.

[Walter F.]

Re: safe operating temp

Different on line comments. Many posters seem to believe the cooler you engine runs the longer oil will last and not break down. Chevrolet according to the Chilton manual seems to feel 238 is safe for your engine and transmission. I get nervous when I see my gauge hitting 230.
I have never really been in heavy traffic on a hot day with my Corvette. To be honest I afraid. And I have a new radiator, water pump and fresh anti-freeze. If I saw the gauge hit 238 or higher I would probably pull over and let the car cool down.

[Ed S.]

Re: safe operating temp

Along those same lines - it is not the effects of the 220+ temp on the block and internal components that concerns me, I just have visions of a radiator or another type of cooling system hose just bursting or having a leak right at the hose clamp where the rubber always seems to deteriorate first because of the pressure from the clamp. The notion of a hose bursting and spewing steaming hot coolant all over the engine compartment is not something I ever want to personally experience.

[Michael W.]

Re: safe operating temp

Different on line comments. Many posters seem to believe the cooler you engine runs the longer oil will last and not break down.

Please post the source of these comments so we can all avoid accidentally going to this website.

That's crazy.

[Terry M.]

Re: safe operating temp

I have been reading that with anti freeze you should never let your temp get over 220. On my 84 the cooling fan does not kick on till 216. At what temp does damage begin to take place on an engine ?

While it is a very different engine than your's (a lot more aluminum) I have seen 240 degrees on my 2008 LS7 with no boil over. However, at that temperature the computer is programed to shut off the AC and turn on the heater full blast. The first time that happened to me I was more than a little alarmed, but the same thing happened to other C6 Corvettes in the caravan we were in (NCRS National Road Tour in St Charles MO). When I questioned the Power Train engineers, I was told the computer is programed to save the engine, even at the expense of the discomfort of the occupants.

Be glad all you have to be concerned with is whether the fan comes on or not. If you are really worried about your engine temperature turn on the heater.

[Patrick H.]

Re: safe operating temp

While it is a very different engine than your's (a lot more aluminum) I have seen 240 degrees on my 2008 LS7 with no boil over. However, at that temperature the computer is programed to shut off the AC and turn on the heater full blast. The first time that happened to me I was more than a little alarmed, but the same thing happened to other C6 Corvettes in the caravan we were in (NCRS National Road Tour in St Charles MO). When I questioned the Power Train engineers, I was told the computer is programed to save the engine, even at the expense of the discomfort of the occupants.

Be glad all you have to be concerned with is whether the fan comes on or not. If you are really worried about your engine temperature turn on the heater.

To follow, even the TCS systems on the early 70s Corvettes were made to adjust the timing in the case of overheating.
The only time I ever had this in my 72 was when sitting in line at the 2004 NCRS National awaiting my photo for the awards. This was before we were even placed on the field to start the show, and there were several cars in line. In addition, I'd just driven across the state to get there.
The TCS kicked in, full vacuum went to the distributor, and engine speed increased. It did work to cool the car down. Of note, the radiator cap (original) worked just fine.

[Duke W.]

Re: safe operating temp

Elastomeric material degradation increases exponentially with temperature. I had a heater hose burst on my SWC when it was only five years old, but modern elastomers are much more resistant to thermal degradation as are modern engine and transmission oils.

I know we all get a little antsy when the temperature climbs to 210 or more, but it won't really do any harm. On modern cars that just have electric fans they may not engage until about 230. Keeping the A/C on will usually help because the fan(s) will periodically engage when the high pressure switch closes. Some systems can be "tricked" into engaging the fan(s) at a lower temperature. In the late 80s Mercedes world the system can be easily modified to engage the fans at less than the normal 105C (221F), but mine hasn't hit that temperature for a long time since I only drive it during the fall to spring. It actually has a mechanically driven viscous clutch fan (albeit small) and the clutch tightens at 100C. The dual electric engage at high speed at 105C and low speed when the A/C pressure switch closes. It even has a fuel cooler than routes freon to the cooler when the A/C is engaged.

The viscous mechanical fans on vintage Corvettes are actually an advantage because if you're stuck in traffic you can always bring revs up to 1500 to 2000 in neutral, which will considerably improve air flow through the radiator. Of course the clutch must be functional and the radiator in good condition.

Also, make sure the engine has the proper total idle advance, which is the combination of initial timing and full vacuum advance - low to mid 20s for base engine cams, mid to high 20s for medium overlap cams like L-79 and all big blocks, and high 20s to low 30s for all small block mechanical lifter cams. Of course, this requires all ported vacuum advance applications to be converted to full time along with swapping out the OE-spec VAC with one that passes the Two-Inch Rule, if required.

Duke

[Terry M.]

Re: safe operating temp

To follow, even the TCS systems on the early 70s Corvettes were made to adjust the timing in the case of overheating.
The only time I ever had this in my 72 was when sitting in line at the 2004 NCRS National awaiting my photo for the awards. This was before we were even placed on the field to start the show, and there were several cars in line. In addition, I'd just driven across the state to get there.
The TCS kicked in, full vacuum went to the distributor, and engine speed increased. It did work to cool the car down. Of note, the radiator cap (original) worked just fine.

True if the TCS or CEC system is factory configured, but all bets are off when one goes to full time vacuum as is often suggested here. The full time vacuum advance may or may not reduce operating temperatures sufficiently for the engine to run comfortably cool.

[Patrick H.]

Re: safe operating temp

True if the TCS or CEC system is factory configured, but all bets are off when one goes to full time vacuum as is often suggested here. The full time vacuum advance may or may not reduce operating temperatures sufficiently for the engine to run comfortably cool.

True.
Had to leave it all connected for the Bowtie judging.

Ironically, we fixed the overheating on another of the 72s here by converting to a full time vacuum even though the TCS was functioning, so I would say that it definitely helps.