Correct engine coolant temperature

[salvatore1]

Originally Posted by QB93Z

I am convinced that the cooling problem with the ZR-1 is related to the bypass flow around the radiator. In both my 1990 ZR-1 and my 1993 ZR-1, I have brand new high capacity radiators (a DeWitt and a Ron Davis) and Haibeck chips.

In both cars when cruising at about 55 mph in sixth gear (about 1600 to 1800 rpm, the coolant temperature will rise to around 225. If I shift to fifth gear, (>2000 rpm) the temperature immediately drops to around 203-205. The drop is rapid (you can see the needle move). This indicates to me that there is plenty of cooling capicity available (ie air flow and heat transfer from the radiator) but that at low rpm most of the water pump output flow is bypassing the radiator through the radiator bypass line.

Under higher engine load, such as running at 80-85 mph the coolant temperature is stable at around 195.

My next research attempt is going to be replacing the thermostat (which also has the bypass flow valve built into it. I may even try to block off all the low rpm bypass flow just to see what happens.

Jim

I know what your saying because I do notice a change in engine speed does affect the temperature almost immediately. But with that said, I'd be very careful about defeating the bypass feature as this may send too much water presure through the radiator and possibly blow it out.

[scottfab]

Originally Posted by salvatore1

Car has about 32K miles. I had partially pulled off the shroud to look at the radiator. but did not get it all the way out. I did not see any bird nests in there, but obviously I wouldn't be able to see sand in the mesh unless I yanked it completely - I really wanted to avoid that if at all humanly possible.

You can use a long bent piece of wire from a cloths hanger to get stuff out.
To avoid getting stuff in there see:
http://www.zr1netregistry.com/ZR1_radiatorscreen.htm
Mine is a stock LT5 in a 90. I run 220 in traffic.
As mentioned by others, keeping the AC on and using 5th gear keeps temp
lower.

[salvatore1]

Originally Posted by salvatore1

Hi,

I know this subject has been visited before, but I'll ask it again anyway. What is the correct engine temperature for the Z? Mine seems too hot for my comfort.

If the car is not moving very fast (i.e. bumper to bumper traffic) the guage starts to climb all the way to top, but then just as it touches the cross hatches a fan kicks in and the needle drops pretty quickly to the 3/4 (still too hot for my comfort). I think the radiator is ok because when the fan kicks in (not sure which one) it does start cooling down. Also, when I'm moving at a good clip on the freeway, the needle will go back to the halfway mark or lower.

I would also like to mention I tried looking at the "digital temperature" via the A/C control and it shows 113 when the guage goes all the way to the top (235) - I guess it's in celsius. After it hits that exact temperature the fan kicks in and it drops as stated above.

Any idea whats happening here?

Thanks
Sal

Guys - I think I found the reason but I'm not sure.

Do any of you know the the sequence of the two fans? When the temperature gets up to about 235 I notice the PASENGER side fan comes on religiously. But I also noticed that the DRIVER side doesn't seem to be spinning at all - does it come on at an even higher temperature or should it have been running BEFORE the passenger side fan?

Thanks,
Sal

[scottfab]

Originally Posted by salvatore1

But I also noticed that the DRIVER side doesn't seem to be spinning at all - does it come on at an even higher temperature

Comes on when AC is turned on.
You can use this to keep it on and lower the coolant temp.

[salvatore1]

Originally Posted by scottfab

Comes on when AC is turned on.
You can use this to keep it on and lower the coolant temp.

it will ONLY come on whith the A/C?

[salvatore1]

Originally Posted by scottfab

Comes on when AC is turned on.
You can use this to keep it on and lower the coolant temp.

My driver side does not come on with or without A/C turned on.

[dbriana]

Originally Posted by salvatore1

My driver side does not come on with or without A/C turned on.

It should come on with a/c, maybe a bad relay? connection?

[scottfab]

Originally Posted by salvatore1

My driver side does not come on with or without A/C turned on.

If the High presure side of the AC line never reaches 240psi then the
fan does not get told to turn on. Check to see if the AC is working.
Does it get cold? If so maybe the fan or (of fan relay) is bad?
Check connection at the fan.

[secondchance]

Originally Posted by QB93Z

I am convinced that the cooling problem with the ZR-1 is related to the bypass flow around the radiator. In both my 1990 ZR-1 and my 1993 ZR-1, I have brand new high capacity radiators (a DeWitt and a Ron Davis) and Haibeck chips.

In both cars when cruising at about 55 mph in sixth gear (about 1600 to 1800 rpm, the coolant temperature will rise to around 225. If I shift to fifth gear, (>2000 rpm) the temperature immediately drops to around 203-205. The drop is rapid (you can see the needle move). This indicates to me that there is plenty of cooling capicity available (ie air flow and heat transfer from the radiator) but that at low rpm most of the water pump output flow is bypassing the radiator through the radiator bypass line.

Under higher engine load, such as running at 80-85 mph the coolant temperature is stable at around 195.

My next research attempt is going to be replacing the thermostat (which also has the bypass flow valve built into it. I may even try to block off all the low rpm bypass flow just to see what happens.

Jim

That is unusual! I never noticed anything similar on 91 nor 94.
Maybe, I just didn't notice? I will duplicate your description later today.

[tomtom72]

Originally Posted by secondchance

That is unusual! I never noticed anything similar on 91 nor 94.
Maybe, I just didn't notice? I will duplicate your description later today.

I agree, I think. It appears to me that my 90 will become more heated if I spend much time in the lower gears, like doing road work where 3rd & 2nd & 4th are used alot....specially if I slow down and cease playing and drive normally. At that point it appears that I heat soak for a good while till the cooling system calms down or catches up to the heat load that I just generated by my sophomoric behavior......it appears that the higher I go in the rev band, and the longer I stay higher in the revs, the more by-passing takes place in my 90's cooling system? It appears if I insist in living up past the 4k mark that after a good while the oil & coolant temps start to spike even if my velocity is at a good clip. I seem to get my best cooling performance when I can keep to about 2k or below in 5th or 6th with a constant speed. Maybe I have something malfunctioning?