First drive on the highway...some questions???

[Roadster]

Took the ZR-1 out to the 74 yesterday, which is about an hour and ten minutes away from my home. Ran extremely well, but do have some questions regarding the coolant temp, clutch noise, and passing speed.....

1- I have Marc's chip in here, so the fans will come on @ 205* and come off @200*. I noticed that driving in 6th gear the temp would go up to around 213* at around 60-65 mph. If I dropped down to 5th gear, the temp would drop to 203* - 200* and stay there. I am not complaining by any means, but trying to understand why the difference in temps in the different gears. 5th gear was running about 2000-2300 rpm's and 5th gear was running about 1600-1800 rpm's for the same speeds. If the fans are coming on due to the temp change, then they aren't depended on the rpm speed? Correct? Maybe I'm missing something here, just curious....

2- Passing speed, when driving along in 5th or 6th gear, traveling @ 60-65 mph and you press down on the accelerator, are the secondaries supposed to open up. The car goes, but I thought I would get a better response. And yes, I realize that the r's are lower, and that if I downshifted to a lower gear, it would have a different result, just wondering how it should be???
Out of first or even moving in 2nd, it's just fine, did my first shift from 1st to 2nd above 6000 r's and I was moving, no miss, bog, anything of that nature. And of course, it feels like the secondaries open up just fine....

3- I noticed this nioise at low speed driving that it seems the throw-out bearing is singing a high pitched note, when I depress the clutch pedal, the noise goes away, and comes back when the clutch pedal is released, moving or standing still. Throw-out bearing????

Thanks for any and all responses...............appreciated....:saluting:

[Demps]

1. Fairly normal for stock. Water pump flowing more volume at higher RPMs.
2. To your question: Secondaries open on a schedule. Not sure on Marc's chip specifics. Bottom line: this is/was a critique of the LT5. There are some developmental stories of an uphill climb in an LT5 that had to downshift where regular car did not.
3. Good chance. Another possibility may be the pilot bearing spinning.
Ted

[mike100]

The dohc design is a little soft below 3000 rpm- you will just learn to drive it a little differently than a small block vette. I give no quarter if and downshift into 3rd sometimes on the freeway just because there is still usable top end left on the powerband.

My last 95 coupe with the blue label ZF made the same exact noises- it is normal although it may vary from car to car. It can be tuned out with careful assembly and blueprinting, but I wouldn't touch it unless something else goes wrong with it. I do not believe the noise is an indication of impending failure or shortened lifespan. ZF's make all kinds of noises from the bearing whine to 'box of rocks' grumbles at low rpm lugging and such. Bill B (ZFDoc) has all the info on this box and his services at http://www.zfdoc.com/.

[We Gone]

Had an issue with water temp on the 93 I did not notice until I changed to Marc's chip.
Running in 6th gear it would get up to 217 and never below 205, so the fans would never cycle off. In traffic it would stay about the same.

It would run a few degrees cooler in a lower gear as the water pressure was up and by passing some at the thermostat.
Long story short changed the thermostat now it only gets to around 210 in traffic and when the fans cycle on it goes back under 200 and they cycle off as they should and stays 190 to 200 at the most in 6th moving down the road.

[Roadster]

1. Fairly normal for stock. Water pump flowing more volume at higher RPMs.
2. To your question: Secondaries open on a schedule. Not sure on Marc's chip specifics. Bottom line: this is/was a critique of the LT5. There are some developmental stories of an uphill climb in an LT5 that had to downshift where regular car did not.
3. Good chance. Another possibility may be the pilot bearing spinning.
Ted

Ted, thanks for the info. So it is not just me noticing that about the LT5!!!

The dohc design is a little soft below 3000 rpm- you will just learn to drive it a little differently than a small block vette. I give no quarter if and downshift into 3rd sometimes on the freeway just because there is still usable top end left on the powerband.

My last 95 coupe with the blue label ZF made the same exact noises- it is normal although it may vary from car to car. It can be tuned out with careful assembly and blueprinting, but I wouldn't touch it unless something else goes wrong with it. I do not believe the noise is an indication of impending failure or shortened lifespan. ZF's make all kinds of noises from the bearing whine to 'box of rocks' grumbles at low rpm lugging and such. Bill B (ZFDoc) has all the info on this box and his services at http://www.zfdoc.com/.


Mike, yes I have found that out, as mentioned above, glad its not just me noticing those differences....and learning how to drive the LT5 as you are suggesting, which is so much fun.....still alot to absorb.......


Had an issue with water temp on the 93 I did not notice until I changed to Marc's chip.
Running in 6th gear it would get up to 217 and never below 205, so the fans would never cycle off. In traffic it would stay about the same.

It would run a few degrees cooler in a lower gear as the water pressure was up and by passing some at the thermostat.
Long story short changed the thermostat now it only gets to around 210 in traffic and when the fans cycle on it goes back under 200 and they cycle off as they should and stays 190 to 200 at the most in 6th moving down the road.

Steve, when I first drove the Z, in local traffic with no AC, the temp would climb up to 238* and then come down when moving. Switching to Marc's chip, without the AC, 217* is the highest I have seen, and 210* the highest with the AC on, it will usually come down to 203*-201* when running the AC.
I am satisfied with where the temps are, and I have no idea if the thermostat
has ever been changed.

[efnfast]

Tom, AC forces both fans on. Probably why you see lower temps with the AC on.

[XfireZ51]

May want to consider pulling radiator and cleaning out the cooling fins. Over the years, fine dust gets in there hindering air flow.

[Racinfan83]

Steve, when I first drove the Z, in local traffic with no AC, the temp would climb up to 238* and then come down when moving. Switching to Marc's chip, without the AC, 217* is the highest I have seen, and 210* the highest with the AC on, it will usually come down to 203*-201* when running the AC.
I am satisfied with where the temps are, and I have no idea if the thermostat
has ever been changed.

That's the way mine was until I took it to Marc. I had him pull radiator and clean it, replace thermostat, and chip it among other things. I don't remember what temp thermostat he put in it - but mine hardly ever goes over 200 now no matter what... So maybe the radiator clean made a huge difference. That sucker was NASTY for having only 18k miles. The lower right third was caked with grease and dirt - Marc said the oil cooler lines has leaked and been replaced - but the oil got all on the radiator and they didn't clean that when they changed the lines. I made a debris screen to keep the bigger stuff out right after I got the car - but the rad was full of dirt and greasy junk...
http://i72.photobucket.com/albums/i178/Racinfan83/Erics%20ZR-1%20Vette/20130923_121026.jpg

[Paul Workman]

May want to consider pulling radiator and cleaning out the cooling fins. Over the years, fine dust gets in there hindering air flow.

Yes! x2 on that. The amount of sand and plant fiber that flushed out of mine was astounding. And, when driving, it is a good thing to avoid driving over the grass clippings resulting from people mowing along the edge of the road. (I found a thick mat of grass clippings pressed like cardboard against the top 1/3 of my radiator.)

[mike100]

I found that residual mist and wet frame sections from the all too common oil cooler line leak will still allow dirt to build up even many months after the repair. As a general trend, i would say to clean the radiator every two years (from both sides). I clipped the pass. side shroud tab to make it easier to remove from the cluster of a/c lines and bracketry.

Besides the large debris, you still need to spray it through with water before each summer.

[USAFPILOT]

2nd will take you to 80MPH, passing is done is 2nd or 3rd.

[Roadster]

Tom, AC forces both fans on. Probably why you see lower temps with the AC on.

Yes, there is a difference, even though it is minimal with Marc's chip.


May want to consider pulling radiator and cleaning out the cooling fins. Over the years, fine dust gets in there hindering air flow.

That's the way mine was until I took it to Marc. I had him pull radiator and clean it, replace thermostat, and chip it among other things. I don't remember what temp thermostat he put in it - but mine hardly ever goes over 200 now no matter what... So maybe the radiator clean made a huge difference. That sucker was NASTY for having only 18k miles. The lower right third was caked with grease and dirt - Marc said the oil cooler lines has leaked and been replaced - but the oil got all on the radiator and they didn't clean that when they changed the lines. I made a debris screen to keep the bigger stuff out right after I got the car - but the rad was full of dirt and greasy junk...

Yes! x2 on that. The amount of sand and plant fiber that flushed out of mine was astounding. And, when driving, it is a good thing to avoid driving over the grass clippings resulting from people mowing along the edge of the road. (I found a thick mat of grass clippings pressed like cardboard against the top 1/3 of my radiator.)

I found that residual mist and wet frame sections from the all too common oil cooler line leak will still allow dirt to build up even many months after the repair. As a general trend, i would say to clean the radiator every two years (from both sides). I clipped the pass. side shroud tab to make it easier to remove from the cluster of a/c lines and bracketry.

Besides the large debris, you still need to spray it through with water before each summer.

Thanks for the suggestions and the pic of the radiator, did that ever need cleaning!!!
I looked between my radiator and the condensor, and found one leaf. And it probably needs a good cleaning as everyone is suggesting. So I may do the hose cleaning front & rear first to see how much dirt I can loosen up. No time to pull the radiator, as the 74 is keeping me busy everyday for the next 2 weeks.

[Roadster]

2nd will take you to 80MPH, passing is done is 2nd or 3rd.

I will keep that in mind, and try it out next time on the highway....thx....

[Roadster]

ok....some more questions....may be general C4 items and not just related to the ZR-1.

On the highway again today, and I've noticed that when moving at speed in 5th or 6th gear taching around 2k or less, that when driving over a bump or slight dip in the road, that the tach neddle will drop a few hundred rpm's and rebound over said imperfection. So is this a common problem with C4's? and what is the fix?

Also noticed that sometimes my volt gauge is all over the place, the needle seems to blink right along with the turn signals, no turn signal, no movement of the volt gauge needle. Also with dash lights lit, the lights in the dash will also flicker with turn signal usage. Common problem, or something I need to check further? I will have to check the digital readout when this happens, but haven't done so yet.

thanks for any info...................Tom

[edram454]

I have a manual fan switch. I can turn on one or both of the fans at any time. In Florida I always have both fans running and it prevents overheating. I should probably take and clean the radiator and get a new thermostat just in case but the manual fan switches are the best. Previous owner did a bunch of things like this on my car. I think he covered all the bases.

ed ramos #3028