Introduction and Overheating (long)

[ChattanoogaJSB]

I lost all of my first lengthy post, so I'll keep this short and try and add only what's necessary. I'm sorry it makes for a less congenial introduction.


91 ZR-1 was bought new by my friends father and driven 7K miles in the first two years. Sold, found again two months ago by my friend and purchased with just about 1K miles more. he had it serviced including new green coolant (but no idea if it was truly flushed), we drove it home 2,800 miles from Oregon to Tennessee in four days. low on power, shop had done three bad secondary injectors but not tested the primaries. I found four bad primaries ohm testing the ecu plug. all injectors I have now done with Accel, which totally restored the power!



On drive in flat country car would not run over 149 mph on a "closed course" in fourth or fifth but did not overheat at cruise. First mountain pass- overheated to 7/8 gauge, when we stopped. This was only when we were pulling uphill, but only going normal speeds. Downhill and flat were fine, temps restored to normal (about 1/3 of temp gauge)



Note when it got hot the overflow was simply ambient temperature and no change of level. Overflow still never seems to move and we have tried two caps.


swapped thermostat with a NAPA unit, but new and old boil-tested fine.


Fans come on. Used registry member scottfab method to refill (thank you!) taking off throttle body coolant line on drivers side as I filled to top.



both intake hoses will run 210 degrees with the fans on idling, system seems full. coolant looks clean. As soon as you ask it to pull a grade the temps go over half to 3/4 and will eventually go to 7/8.


My thought is that the radiator is probably flowing very minimally, having sat with (the orange?) coolant in it for possibly many, many years at a time.


can anyone help give me any other ideas? should I pull the radiator and have it cleaned or can i try and clean it in place?



I'm a regular on the CF but new here- I am not afraid to work on the car but I am trying now to get a little group consensus. I've got a '64 coupe that I rebuilt after a semi truck hit me, have had a couple of 69's and bought an 09 new. I also had an Lt-1 powered 95 Firehawk.


My friend has been a lifelong Porsche fan (as was his father) and I am desperate to make his ZR-1 the "better car" I know it can be!


Thank you in advance for any advice!


Benton

[ChattanoogaJSB]

Will try and post pics mid day, just to show off the car.

[grahambehan]

first thing to check would be debris between the AC condenser and the radiator, they like to collect garbage, leaves etc.
Graham

[Ccmano]

Benton, welcome to the addiction! Sorry to hear of your troubles. You came to the right place. I had to read your post a couple times to get a clearer picture of what is going on. It sounds like the car operates relatively normally until a large load is placed on the engine. I take it replacing the thermostat changed nothing.

Just to eliminate the obvious have you looked in the air intake area ahead of the radiator stack to see of there are any obstructions like leaves or a plastic bag? These cars act like vacuum cleaners and suck up all kinds of crap.

Next, it would be good to get more accurate temperature readings, the dash gage is not reliable. Do you know how to get temperature reading on the AC display?

1. Push and hold up and down (each side of Fan Control button) until you get zeros in display on left.
2. Then push up button to right until you get to 16 in the display.
3. Then push center fan button to read digital coolant temperature in degrees C continually in the display until you hit the temperature button. The car can be driven in this mode to get ongoing temp readings.
80 C is 176 F
85 C is 185 F
90 C is 194 F
95 C is 203 F
100 C is 212 F
105 C is 221 F
110 C is 230 F
115 C is 239 F
120 C is 248 F
125 C is 257 F
130 C is 266 F

Since the issue, if I read this correctly, is only under load I would suspect the radiator first. Also check the spark plugs to see if there is any sign of a head gasket issue (while unlikely) just to be certain.
H
:cheers:

[Ccmano]

If you haven’t already done so, read up on the cooling system and it’s issues. Dynomite provides an excellent review in the “Solutions” sticky at the top of this Technical section.
H

http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070558

[lfalzarano]

So it only overheats when the nose of the car is pointing “up hill” and not in any other direction? I assume that when driving up hill, the revs are a lot higher than when driving down hill or on level ground. If that is the case, it could be the water pump internal blade is going bad. Just a hunch... & JMHO


Lou

[efnfast]

What does orange coolant do to the system?

[DRM500RUBYZR-1]

Follow the instructions in post # 4, and replicate the driving situation and observe the temperature on the HVAC display.
This will confirm the actual temperature far, far better than the gauge.
The gauge is non linear, and is known to be highly inaccurate at times.


While it does sound as if you have a problem, let's be certain first that there is.


Next look for and clear the debris as described also above. Hoover wishes their vacuums worked half as well as the C-4 cooling air intake that indeed sucks up everything, including soda cans!


Next, while monitoring the true temperature on the HVAC, start and watch the fan behavior.


Fan 1 should come on exactly at 228. When it does, you should see an immediate decrease in the rate of temperature rise.
If it succeeds in keeping you at or below 228, you will not see the 2nd fan activate, as it comes on at 240 I believe.


If all of that goes as it should turn on the AC which should bring on both fans immediately regardless of temperature.


If all of that checks out, take a careful look and feel of the lower radiator hose, to ensure that it is not collapsing under load.


If OK, it's then onto the water pump function and radiator function.


The fact that it is not pushing coolant into the overflow tank causes me to want to make sure it is really overheating before going any further.


7/8 on the gauge would likely eject coolant when shut down, but as mentioned 7/8 on that gauge may mean nothing, so start simple first.


You will find and correct it!
Marty

[ChattanoogaJSB]

Wow! So many welcoming and helpful replies. Let me try and address a few comments.

1) yes I’ve read most of the forum stickies on this topic but at different times; I will revisit

2) the orange coolant seems to gum up more than the green, we are trying to find out if we have a photo from our inspection that shows it. I do not but my friend might. That’s all academic now but it might point toward being gummed up.

3) I do tend to believe it’s an obstructed radiator, I’ll have to find out what I can leave in place on removal. Hopefully the ac condenser and oil cooler can stay plumbed.

4) my friend drove it today. In just ten minutes of hilly driving (not up the mountain) it peaked at 110 C / 230 F with one fan on. Ac brings on both fans. He did the temp display procedure.

5) I will double check the plugs for any visible “steam cleaning”

6) I still owe you guys photos!

7) anything I missed replying to I will address after dinner and my thanks again!

Benton

[ChattanoogaJSB]

http://i65.tinypic.com/x5y4o9.jpg

Analog vs digital at 230 degrees actual

Similar to what my IR gun shows on engine

[ChattanoogaJSB]

http://i64.tinypic.com/i4323a.jpg

[ChattanoogaJSB]

http://i67.tinypic.com/flzh53.jpg

[ChattanoogaJSB]

Mine-
http://i68.tinypic.com/10h91mc.jpg

[ChattanoogaJSB]

http://i64.tinypic.com/20rwvfk.jpg

Us on the way home!

[efnfast]

I'm worried the orange coolant has muddied things up.

[TX '90 ZR1]

http://i65.tinypic.com/x5y4o9.jpg

Analog vs digital at 230 degrees actual

Similar to what my IR gun shows on engine

I notice in the pic that the oil temp is pretty low on the guage for a water temp like you have. The oil temp guage is probably not real accurate either, but you might want to use actual oil temp as a cross reference.
By the way, NICE LOOKING CAR!!

[carter200]

http://i64.tinypic.com/20rwvfk.jpg

Us on the way home!


There is the problem.... you are upside down. Car cools better when wheels are on the ground ;)

[efnfast]

They must have the "Red Button" from men in black

[DRM500RUBYZR-1]

Wow! So many welcoming and helpful replies. Let me try and address a few comments.

1) yes I’ve read most of the forum stickies on this topic but at different times; I will revisit

2) the orange coolant seems to gum up more than the green, we are trying to find out if we have a photo from our inspection that shows it. I do not but my friend might. That’s all academic now but it might point toward being gummed up.

3) I do tend to believe it’s an obstructed radiator, I’ll have to find out what I can leave in place on removal. Hopefully the ac condenser and oil cooler can stay plumbed.

4) my friend drove it today. In just ten minutes of hilly driving (not up the mountain) it peaked at 110 C / 230 F with one fan on. Ac brings on both fans. He did the temp display procedure.

5) I will double check the plugs for any visible “steam cleaning”

6) I still owe you guys photos!

7) anything I missed replying to I will address after dinner and my thanks again!

Benton


Benton,
What was the ambient temperature during your drive?


230 is not alarming.


The fact that it held below 240 is a very good sign, as fan 1 was controlling it fine.


The oil temp may not be too far off if the coolant was at 230, but yes a tad low. Remember, all of those gauges are non linear.


Do all the checks that were suggested, as 230 is a bit high, but certainly not where the gauge was suggesting.


As said NICE car!


Great to see the smiles!!!!


Smiles are standard and excessive in this car!


Marty

[jss06c6]

"Note when it got hot the overflow was simply ambient temperature and no change of level. Overflow still never seems to move and we have tried two caps."

I would make sure you don't have air trapped in the system.. need to "burp" the system when you swap coolant.. just a thought..

Sent from my XT1585 using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)

[ChattanoogaJSB]

Benton,
What was the ambient temperature during your drive?


230 is not alarming.


The fact that it held below 240 is a very good sign, as fan 1 was controlling it fine.


The oil temp may not be too far off if the coolant was at 230, but yes a tad low. Remember, all of those gauges are non linear.


Do all the checks that were suggested, as 230 is a bit high, but certainly not where the gauge was suggesting.


As said NICE car!


Great to see the smiles!!!!


Smiles are standard and excessive in this car!


Marty

Hi Marty - ambient today was about 90. My friend and I can entertain the dash gauge isn’t reliable. 230 (actual) is also a number I can tolerate. Is that universally acceptable around here? It would be acceptable on my wife’s x5 I know but unusual on - say- my 67 mustang. I guess the next question would be what the upper limit would be to keep driving?

Oil temp is consistently low on the dash instrument. I guess we need to find which number the ecm will display it in the air conditioning window.

My friend does have the fsm on dvd but I don’t at my home.

Thank you so much for the support and kind words. The injector swap out a smile on my face and started me looking for one of my own!

[ChattanoogaJSB]

"Note when it got hot the overflow was simply ambient temperature and no change of level. Overflow still never seems to move and we have tried two caps."

I would make sure you don't have air trapped in the system.. need to "burp" the system when you swap coolant.. just a thought..

Sent from my XT1585 using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)

I grappled with the common issue on this forum of trapped air I agree. At this point I have to say I have it bled- evidenced by the coolant flow from the TB hose on the drivers side (removed and pointed up) when filling the reservoir tank by the windshield.

[Great White]

Have you pressure/leakdown tested the cooling system? I'm concerned since you said the car had orange coolant in it, as these are NOT Dexcool cars. Dexcool can have very ill effects on systems not designed for it. (Failed gaskets, hoses, and the like.) When these components fail, the radiator can become clogged with debris or sludge from dissolving gaskets and hoses. Something to consider.

[ChattanoogaJSB]

Have you pressure/leakdown tested the cooling system? I'm concerned since you said the car had orange coolant in it, as these are NOT Dexcool cars. Dexcool can have very ill effects on systems not designed for it. (Failed gaskets, hoses, and the like.) When these components fail, the radiator can become clogged with debris or sludge from dissolving gaskets and hoses. Something to consider.

We haven’t done a leakdown test on it. We can’t find any evidence it had dexcool in it, my apologies for not being clear- we were indeed trying to go back and find a photo from the sale that might show if it had dexcool in it which would be problematic.

The only photo we found showed the overflow from above and was green if anything.

[ChattanoogaJSB]

Just to make sure I’m asking the right question - what do you folks see for running temps pulling up a grade? At level cruise? Our summer ambients are about 92 right now. (As measured by the ac display if possible, sounds like the dash gauge is not a consistent measurement)

Just to confirm- even at 106 degrees ambient in Utah it ran less than half the temp gauge on the interstate at level ground. It’s the 230 degrees plus pulling that has us so concerned

[Great White]

Gotcha, if it was green coolant you should be okay. I've seen 230 degrees on a hot day (98 degrees F) in stop and go traffic with my A/C on. My car has the Haibeck chip, so the fans come on early as well. Not sure how old my radiator is, but shortly after driving my car that week in close to 100 degree ambient temps the radiator failed (a side tank cracked.)

I would still recommend the pressure/leakdown test. A leakdown test can tell you a lot about the integrity of your cooling system. A radiator upgrade might be in your near future... It sure is for me.

[Ccmano]

If the car has the original chip 230 is not a problem, particularly with ac on in hot weather. The standard calibration doesn’t even turn the fans on till 236. These engines were designed to run at that temp. Over 240 and I would start to be concerned. Get a Haibeck chip and the temps will come down. So far I don’t see anything alarming.
H

[ChattanoogaJSB]

There is the problem.... you are upside down. Car cools better when wheels are on the ground ;)

I hate it when they look flipped! It doesn’t show flipped on my screen so I don’t know how to fix. The new owner is driving in this photo and I’m on the left!

[ChattanoogaJSB]

Ccmano- thank you for the supporting comments, also those from great white.

I’ll try and run it and see if it tempts going over 236 F and explore the dash gauge

[carter200]

I hate it when they look flipped! It doesn’t show flipped on my screen so I don’t know how to fix. The new owner is driving in this photo and I’m on the left!


I hope you know I was just funnin' you, Z owner to Z owner ;) Most everybody knows me or of me and I like to have fun when I can. Nice clean white Z you have.

[ChattanoogaJSB]

I hope you know I was just funnin' you, Z owner to Z owner ;) Most everybody knows me or of me and I like to have fun when I can. Nice clean white Z you have.

Oh, totally! I’m sorry I didn’t convey it! The first and second gen side of the corvette forum is actually full of a bunch of funny dudes- even at most of their ages those guys are sharp. In all seriousness I have seen tinypic hosting flip images but for some reason mine is normal on my screen.

Also I wish the car was mine- I may pick one up with some more mileage! The engine sound is intoxicating when you’ve been around pushrod v8’s your whole life!

[ChattanoogaJSB]

(deleted duplicate post)

[ChattanoogaJSB]

I do need to read the WHOLE cooling thread tonight but I stumpveld on this early entry in it today which kind of confirms what you guys are telling me about normal temps - and also what I might expect out of a bigger radiator.

I also see Dewitt’s makes a c4 90-96 radiator and their reputation is excellent but I’m not hopeful a zr-1 radiator part is the same. Pretty sure my lt-1 reverse cooled. http://i67.tinypic.com/2vuk9le.jpg

Also my friend has considered doing the Haibeck (sp, sorry) chip primarily for the fan programming. Thoughts on this and best place to buy?

I am such a noob!

Benton

[Ccmano]

Driving the car with the Haibeck chip will be like a night and day difference.
There is only one place to buy it, from Mark Haibeck. You won’t regret it.
http://www.zr1specialist.com
H
:cheers:

[ChattanoogaJSB]

Driving the car with the Haibeck chip will be like a night and day difference.
There is only one place to buy it, from Mark Haibeck. You won’t regret it.
http://www.zr1specialist.com
H
:cheers:
H-

That’s a strong recommendation! Almost seems like a great place to start- lots of improvements to appreciate even if it does need a radiator.

Thank you!

Benton

[A1990]

You can meet Mark and bid on one of his chips at Corvettes of Carlisle this weekend!


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[ChattanoogaJSB]

You can meet Mark and bid on one of his chips at Corvettes of Carlisle this weekend!


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

It may be too far for us this weekend! My wife I attended one (2012?) year with my Western PA in laws and had a great time. The swap meet alone was worth the admission.

I would guess my friend will reach out to get one. We are going to run it up and down our little mountain and see if the temp holds under 240 degrees F with the AC display running. Will be some indicator if the system is ok- in general- then look toward using the Haibeck chip to get the fans on earlier (with a host of other improvements I see)

[secondchance]

Dewitt radiators for C4 is the same for ZR-1s. I have been running dual row Dewitt since 2015 and totally happy. Make sure it's dual row for manual tranny.

[ChattanoogaJSB]

Dewitt radiators for C4 is the same for ZR-1s. I have been running dual row Dewitt since 2015 and totally happy. Make sure it's dual row for manual tranny.

Thank you! I am 7 pages into the 13 pages of cooling thread elsewhere here. Good stuff!

Was going to ask as I was reading if the radiator is in fact a shared part with a c4 manual trans radiator. Dewitts suggests it is.

Perhaps a second question - I am curious if the Champion unit I’m beginning to see is a good fit. I just put one in my fastback mustang and I’m impressed with the build quality AND price.

[rkreigh]

the orange dexcool stuff is bad news for the lt5 head gaskets and I would get rid of it


run the green stuff, you'll be glad you did.

[ChattanoogaJSB]

the orange dexcool stuff is bad news for the lt5 head gaskets and I would get rid of it


run the green stuff, you'll be glad you did.

Yes, we have fresh green in it and now believe it has had green in previously

[rkreigh]

fyi,


I was shocked, after about 4 years and 30k miles a brand new radiator was about 40% packed with crud.


the bigger ron davis seemed to clean up easier than the stocker, but I was surprised just how dirty it was after that amount of miles from normal highway use.

[ChattanoogaJSB]

fyi,


I was shocked, after about 4 years and 30k miles a brand new radiator was about 40% packed with crud.


the bigger ron davis seemed to clean up easier than the stocker, but I was surprised just how dirty it was after that amount of miles from normal highway use.
It’s definitely on my mind that it could be restricted. Certainly would explain heating up under load on only.

Weather has improved and I’m going to test drive it today using the lcd temp readout and will report back. The chip is a no brainer whether I need to put a radiator in now or not.

Thank you for the reply!

[WARP TEN]

My '93 was getting a bit hot at about 40,000 miles. I had my mechanic remove the radiator and it turned out to be about 40% plugged with debris. He hosed it out and replaced it; I added a 1/4 inch hardware cloth mesh screen to the air opening underneath and never had a problem again. Also had Marc add a screen to the '95 just in case. Never had to install an aftermarket radiator. This is simply a problem with the bottom feeders.--Bob

[ssrszz4]

The stock radiator is junk if you ever take it out replace it with a better radiator money well spent.

Sent from my XT1585 using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)

[ChattanoogaJSB]

A couple more folks have responded and I didn’t want to be too long between visits here because I appreciate the feedback. I’ll reply tonight with the notes from my voice memo I made yesterday testing the system after the burp.

The short- short version isthe car drove beautifully and thanks to everyone’s help here could be said to cool “as designed.”

The data might be handy for someone later on so I’ll post.

Owner will do the Haibeck chip now and the radiator as a good precaution in a month or so as we have time between my projects and his two.

Probably Dewitts. No one on the c1/c2 forum has anything but high praise for them.

Benton

[ChattanoogaJSB]

Here are my note of temperature based on where I am on the drive and some notes on condition. Pardon my handwriting.

I feel with everyone’s help I have a much better understanding of the cooling system and it’s next upgrades- my thanks again and for the warm welcome.

http://i64.tinypic.com/6ydueo.jpg
http://i63.tinypic.com/2uxv14i.jpg

http://i64.tinypic.com/2ushk6v.jpg

I started on one mountain, ran down, down the valley road and back up the other. The climbs are only about 1,000’ so not huge but significant

[Ccmano]

Very nice documentation. I see no issues here whatsoever. I see your ambient temp was 82’, keep in mind as ambient temps rise so will your engine temp. Enjoy your Z. When the Haibeck chip is in you will enjoy it even more.
H
:cheers:

[ChattanoogaJSB]

Very nice documentation. I see no issues here whatsoever. I see your ambient temp was 82’, keep in mind as ambient temps rise so will your engine temp. Enjoy your Z. When the Haibeck chip is in you will enjoy it even more.
H
:cheers:

Absolutely. We routinely see 15 degrees hotter weather for a period in summer.

Haibeck will be welcome.

Guess I need to find my own Z now...but where to put it?http://i63.tinypic.com/20hajwn.jpg