dozerman1

I just purchased a 1989 vette w/383 auto. I completely overhauled the engine, I added a higher volume radiator fan, New anti freeze plus a bottle of the liquid extra water coolant (forgot the name. says it will reduce engine by 20 degrees). I installed a new 165 degree thermostat, new fan wiring for the fan to come on at 185 and shut back down at 170..... Here is my question.... when I first start The engine, the temp goes to 238 degrees before it goes back down to th 190 degree range. If I have the a/c on the temp stays at around 210. This just seem right to me... anyone got any ideas....

vader86

Looks normal for a stock fan programming and stock radiator. Corvettes tend to run hotter for emissions reasons.

The main fan should not come on, unless the AC is on, until 228. The Aux fan, if you have one, at 238F. The main fan is ECM controlled and the Aux fan in front of the radiator is run by a temp switch in the cylinder head.

Are you sure your wiring job is operating the main fan at the temps you specify? Sounds to me like it is not. That temps do come down at all or will hold with the AC on tells me there is not a big issue.

I upgraded to a DeWitts radiator, which solved all temperature issues with my 398. If your fans are working as you say, the 383 may just need the extra cooling.

Whaleman

Could the thermostat be sticking? It should not go this high before coming down. I would replace the thermostat with a 180 from Ecklers. I don't know much but I have never heard of a 165 corvette thermostat. They seem different and work great for me. Dan

s carter

One basic check any time these cars run hot is take a knee and give the front of radiator and the space between the a.c. For road debris, one plastic shopping bag your running hot

dozerman1

The fan is controlled by the temp sender not the ECM. ( I bypassed that Sensor) There is no front fan, only the one behind the radiator. I believe that the radiator has been replace by a heavier duty one. It is not the original, It appears to be about 3 in thick. The fan does come on and off at the temps I stated, that's why I can't understand why it gets so hot before it cools back down.

WVZR-1

You're relying on the analog temp gauge for values?

You need to get it on a 'scanner' so can actually evaluate the temps the fans are actually turning on and use the scanner for some longer runs to actually evaluate the entire cooling system.

dozerman1

I installed an Intellitronix digital instrument cluster and I believe the fan coming on at 185 is correct, and shutting off at 170. The new fan is real loud so you can heard it without any problem. What kind of scanner are you talking about?

vader86

He's talking about a scanner to read the ECM's data directly, that hooks up to the OBD port above your right knee. That will show you what temperature the computer sees vs what is on the digidash.

But if you bypassed it entirely then it won't matter much. If you have already changed to a double row radiator you should not hit those temps. Is the WP weeping?

WVZR-1

It matters 'much' the CTS used for ECM/PCM is assembled to very close tolerances since it's an 'emission's device'. The OP's gauge is getting temps from a cylinder-head and whatever switch he has is also quite likely in a cylinder-head so a 'SCANNER' would allow him to evaluate/compare everything that he has. I'd say 'MATTERS MUCH'. OP hasn't mentioned 'tossing' the 1227165 ECM for engine control.

OP - I'd be interested in knowing the BRAND and PART# of your CFS (Cooling Fan Switch). Many in the C4 forum would be very interested. CFS values and performance get's debated/argued frequently. I don't argue but am interested.

vader86

I dont see how it really matters at all. If you go by the digidash temperature and the fans are coming on at 185 by that gauge, and that temp will be reached pretty quickly in a garage, probably within 20 minutes at idle, then the fan is working as he says it is. The only check is that the temperature readout is completely wrong and whatever he sees in the car is not at all what it actually is.

If he has bypassed the ECM control to run the main fan, then ECM no longer controls fan operation for the A/C, and is not shutting the fans off at highway speeds either. This is not a good idea.

I dont believe it is working like he thinks it is, so I don't disagree that it would be a good idea to see what temp the ECM is seeing, but it should make no difference to how hot the car gets IF he has it wired up like he's telling us.

TheBlaster9001

Have you let the car warm up, at idle, to verify that the fans come on when you think they should? Could it be that the fans are still wired to the ECM? To me, this seems like how my girlfriend's stock 86 works - no fans till over 220 (as seen on the dash), then it comes down with the fans. My 85 has the front fan set to come on without the ECM, at high temps/loads or at idle. The main fan is controlled by the ECM, and tuned so it comes on at 190 degrees (as seen on the dash).
I see no reason that your car would continue to warm up above 200 if the fan was on. I suspect something is wired funny, and the fan isn't coming on, debate about the sensors aside.
If the fan is spinning when the dash indicates 200 while temp is on its way up, I can't see how the temp would continue to 230, then come back down, since the fan is spinning the whole time.

Cruisinfanatic

Did you remove the radiator and clean it?

bjankuski

Here is a thought, the thermostat is located in the middle of the intake manifold and if there is no waterflow through it before it opens, it may cause the cylinder head where the temperature sensor for the dash is located to read hot. I have seen this before and the fix it to drill 2 small 1/8 holes in the thermostat to get some water flow to the thermostat so it opens up faster. If there is no flow it takes a while for the hot water from the heads to heat the intake and get the thermostat to open.

This condition is most pronounced on the initial start-up of the day and seems to be less of an issue after the engine stabilizes in temperature. That being said I had a 1990 chevy pick-up with a 350 that would do this all the time in the winter and adding the small holes eliminated the problem.

dozerman1

I just ran the car today and it got to 241 degrees with the fan on. finally I got it moving about 40mph and it started cooling back down. and reached 175 then back up and down from 175 to 200. doesn't make sense to me......

dozerman1

That sounds exactly what is happening. and I am using the cyl head temp send to qaactivate the fan and also to read the temp gauge..... I'll try the holes.....on another note do you have any idea how to disarm the vats I have tried everything I have read but sometimes it comes on when I open the drivers door. and I have to disconnect the battery to stop the d...m horn from blowing..

dozerman1

This is the digital temp gauge on the intellitronix inst. cluster.

bjankuski

I have a question on this, when the car was at 240 degrees was there any heat coming out of the radiator? In other words was the coolant flowing through the radiator? The answer will determine if you have a water flow issue or a radiator heat transfer to air issue.

dozerman1

I drilled 2---1/8 inch holes in the thermostat and that solved the problem.... like bjankuski told me.. It seems to work ok now... Thanks for your help!!!

bjankuski

No problem.

dozerman1

Does anyone know if the fan should continue to run after the engine is shut off, to continue to cool it down..