Need a ZR1 cooling system expert
10-09-2013, 06:18 PM
#1
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Need a ZR1 cooling system expert
Hi
I have a new and baffling problem with my 1990 ZR cooling system. About 2 years ago I rebuilt my cooling system and it has performed flawlessly ever since. Yesterday morning I started the car and noticed that while warming I was not getting any heat from the HVAC. The early heat is normal until the heated conditioned air is delivered. I also noted that the oil temp and engine temp gauges hadn't moved. I decided to let the car idle and watch the gauges until they moved. I waited 5 minutes !. Still no heat. I opened the hood and removed the res tank cap and there was no flow through the air bleed tube in the tank. This is not usual at all. When I went back to the instruments I noted that the engine coolant gauge was rising rapidly towards the hash marks and I shut the engine off. I did this about 4 times always watching the engine temp and shut it off before it got too hot. On the 5 th start up the gauge rose and then dropped back to normal and I noticed that I was now getting heat. All of the above is not normal. I took the ZR for a short drive and everything was normal. This AM I started the car and the temp gauges did not move and there was no heat. I checked the air bleed and no flow. After a few starts the gauge started reading normal and the heat came back.
Two years ago when I rebuilt the cooling system I did the following
Cleaned between the radiator and evap. new water pump, new samco hoses and clamps, new OEM NOS thermostat ( I even discussed the style of the thermostat with Mark H.). I used the Mark H. method of filling the cooling system and it worked great.
For just over 2 years the system has been fantastic. I have driven 400 miles in summer heat that was over 100 deg with the HVAC pumping out cold air and the engine cooling system keeping the car at about 200 deg with no problems at all. My gut feel (and the FSM) says it is the thermostat but am curious if anyone else has had a similar problem.
Thanks
Don in VT
I have a new and baffling problem with my 1990 ZR cooling system. About 2 years ago I rebuilt my cooling system and it has performed flawlessly ever since. Yesterday morning I started the car and noticed that while warming I was not getting any heat from the HVAC. The early heat is normal until the heated conditioned air is delivered. I also noted that the oil temp and engine temp gauges hadn't moved. I decided to let the car idle and watch the gauges until they moved. I waited 5 minutes !. Still no heat. I opened the hood and removed the res tank cap and there was no flow through the air bleed tube in the tank. This is not usual at all. When I went back to the instruments I noted that the engine coolant gauge was rising rapidly towards the hash marks and I shut the engine off. I did this about 4 times always watching the engine temp and shut it off before it got too hot. On the 5 th start up the gauge rose and then dropped back to normal and I noticed that I was now getting heat. All of the above is not normal. I took the ZR for a short drive and everything was normal. This AM I started the car and the temp gauges did not move and there was no heat. I checked the air bleed and no flow. After a few starts the gauge started reading normal and the heat came back.
Two years ago when I rebuilt the cooling system I did the following
Cleaned between the radiator and evap. new water pump, new samco hoses and clamps, new OEM NOS thermostat ( I even discussed the style of the thermostat with Mark H.). I used the Mark H. method of filling the cooling system and it worked great.
For just over 2 years the system has been fantastic. I have driven 400 miles in summer heat that was over 100 deg with the HVAC pumping out cold air and the engine cooling system keeping the car at about 200 deg with no problems at all. My gut feel (and the FSM) says it is the thermostat but am curious if anyone else has had a similar problem.
Thanks
Don in VT
10-09-2013, 07:18 PM
#2
Tech Contributor
Thermostat
You will definitely get the correct Thermostat from Marc
I had a NEW water pump impeller fall off one time.....so all sorts of strange things can happen.
It seems to me that the coolant should be circulating within the engine only until the thermostat opens at 180 deg. So the Injector Housing Coolant manifolds should be getting warm even before the thermostat opens allowing coolant circulation through the radiator.
I always put a hand on each (left and right) Injector Housing Coolant Manifold to make sure each is getting warm (should be in less than a minute)
Last edited by Dynomite; 10-09-2013 at 10:48 PM.
10-09-2013, 10:09 PM
#4
Race Director
I have had 2 thermostats with broken springs so far. The one in there now broke one day and the engine temp dropped over 25 degrees which had me concerned. I stopped and looked under the hood just to see if something was up. Everything looked fine so when I got back on the freeway I nailed it to get the bypass working and see if that would make any difference. Well, their was a difference ! It had noticeably more power!
I still haven't changed it.
I still haven't changed it.
Last edited by Zrxmax; 10-10-2013 at 12:31 AM.
10-10-2013, 09:43 PM
#7
Melting Slicks
I have had 2 thermostats with broken springs so far. The one in there now broke one day and the engine temp dropped over 25 degrees which had me concerned. I stopped and looked under the hood just to see if something was up. Everything looked fine so when I got back on the freeway I nailed it to get the bypass working and see if that would make any difference. Well, their was a difference ! It had noticeably more power!
I still haven't changed it.
I still haven't changed it.
There are 2 downsides. If you have a stock radiator you could blow out the sides, that's what the bypass was for and in temps below about 65 degrees your heater does not work too well and the motor does not get hot enough to go into closed loop, you can put a piece of cardboard in front of the radiator to increase the heat and buy a larger flow radiator to correct the other.
Tyler
10-11-2013, 09:32 PM
#9
Race Director
If you do a search on My name you will find extensive discussion on what is happening when your main thermo spring breaks. Its like cutting out the spring which actually defeats the bypass function in the system.
There are 2 downsides. If you have a stock radiator you could blow out the sides, that's what the bypass was for and in temps below about 65 degrees your heater does not work too well and the motor does not get hot enough to go into closed loop, you can put a piece of cardboard in front of the radiator to increase the heat and buy a larger flow radiator to correct the other.
Tyler
There are 2 downsides. If you have a stock radiator you could blow out the sides, that's what the bypass was for and in temps below about 65 degrees your heater does not work too well and the motor does not get hot enough to go into closed loop, you can put a piece of cardboard in front of the radiator to increase the heat and buy a larger flow radiator to correct the other.
Tyler
One thing I have noticed is the borderline heating dynamic even when a good 180 thermostat is in service. If you set the temperature at 78 or below it blows cool... if you set in at 80 to 85 and it blows hot. Their is no variablilty in the temperature setting.
I ran the big mouth air scoop for a while several years ago. In the hottest comparison test that I could determine like 105 to 110 degrees driving through Baker California. The difference in engine temp was 3 or 4 degrees.