Defective Thermostats

[Marc Haibeck]

I have noticed a defect in new Stant engine cooling thermostats.

For details see:
http://www.zr1specialist.com/HAT%20Web/facts%20and%20failures/thermostat.htm

[Paul Workman]

:thumbsup:

Once again, the "Brothers of the Beast" are fortunate to have you to support us. Thanks again, Marc!!

P.

[Kevin]

thanks for the great info marc, we'd be lost without you

[mike100]

Makes me feel a little better about making the effort to find an oem one. Hopefully Stant will address the issue on future production runs.

[Blue Flame Restorations]

Thanks, Marc. Good to have your expertise.

Brett

[efnfast]

I'm new to this gig, but I love that the support that a guy like Mark will take the time to put a post out there just to let us owners know there is s problem. Thanks Mark. Can't wiat until I can afford to ride to Chicago for the new 510hp upgrade. I can't imagine what 500 hp feels like.

[efnfast]

Geez, look at the typos. I need to slow down.

[XfireZ51]

Anybody need an OEM one, its used but in very good condition.

[tomtom72]

Thank you Marc for the head's up! :thumbsup::thumbsup:


By extension should those of us that buy from the local chevy store check the stat we get going fwd?

[Marc Haibeck]

Up until about six months ago we were acquiring thermostats from the local GM dealer. I never received a defective thermostat from GM. Over the past two years the GM price increases have added up to a ridiculous level. That drove us to acquire them from other parts suppliers.

It’s easy to tell if you get a bad one. Push up on the bypass valve seat. The difference between the correct five pound spring and the incorrect one pound spring is pretty stark.

[Migfly]

Thanks a Million Mark,

Good to have you on here indeed. New to this car myself and have a few questions to rest some worries. First I do understand that vettes have tendencies to run hot, I am told. I do however smell an occasional coolant burning odor when the car gets hot after some driving. Mind you, black car in Florida and what I mean by hot is around 3/4 mark on the gage, guessing around 235F if i am intrapolating degrees properly when stopped in traffic. However, returning to around 1/2 on the gage 190F more or less once I get up to speed. Being mechanically retarded, I did check the following..
Oil good, clean and serviced before purchases
Air filter, AC delco fair, not super dirty, but mostly yellow with some dirt built on, but not needing replacing.
Coolant reservoir ( passenger very front white tank) above cold line level slightly with good green coloring.
Question...
1. All normal don't mess with it?
2. Might want to consider a change in the thermostat to have run cooler down here?

Thanks,
Manny :cheers:

[secondchance]

Thanks a Million Mark,

Good to have you on here indeed. New to this car myself and have a few questions to rest some worries. First I do understand that vettes have tendencies to run hot, I am told. I do however smell an occasional coolant burning odor when the car gets hot after some driving. Mind you, black car in Florida and what I mean by hot is around 3/4 mark on the gage, guessing around 235F if i am intrapolating degrees properly when stopped in traffic. However, returning to around 1/2 on the gage 190F more or less once I get up to speed. Being mechanically retarded, I did check the following..
Oil good, clean and serviced before purchases
Air filter, AC delco fair, not super dirty, but mostly yellow with some dirt built on, but not needing replacing.
Coolant reservoir ( passenger very front white tank) above cold line level slightly with good green coloring.
Question...
1. All normal don't mess with it?
2. Might want to consider a change in the thermostat to have run cooler down here?

Thanks,
Manny :cheers:

Hi, Manny,

I use to live in Lake Mary and work in Kissimmee. So, I am quite familiar w/ weather in that part of the country.
First, analog gauge is really not that accurate. However, based on my later 94 Z, on hot days w/ AC running, at time,s digital gauge would go up to 230+ - not good!

I would suggest Marc Heibeck chip which would allow lower temp fan activation. Also, have the radiator removed and fins cleaned out or, better yet, replace w/ a new NOS unit. Lowest price I have seen is corvetterecycling.com - $99.
Lastly, one 1/8" hole on the flange of the 180* thermostat will generally reduce temp reading by 5-10*. However, real hot day, AC on and stop and go traffic will eventually increase the temp to 230 plus.
160* stat might help but make sure the stat has a bypass valve. If abscent, you will blow out the radiator. I know - happened to me.
If you need to talk to a good Corvette mechanic call Robbie Hooper at Corvette Master's. His shop is behind Roger's Corvette in Maitland/Winter Park area off of 17-92.

[Migfly]

Hey 2nd chance,

Thanks for the heads up. Just waiting to convert the A/c in the next few weeks and get the A/C serviced then was planning to have Robbie check the car over. He is very nice and knowledgble about the LT5. Will consider any of those items suggested. Thanks very much.

[Paul Workman]

Hey 2nd chance,

Thanks for the heads up. Just waiting to convert the A/c in the next few weeks and get the A/C serviced then was planning to have Robbie check the car over. He is very nice and knowledgble about the LT5. Will consider any of those items suggested. Thanks very much.

Marc's calibrations feature having both fans come on at 205ºF and turn off at 200ºF. In the mean time you can try turning on the AC. BOTH fans will come on. It seems counter-intuitive to turn the AC on when the car is starting to over heat, but it works except on the hottest days.

Congratz on the Z, BTW!! Welcome to the Brotherhood of the Beast!
Are you coming to the gathering at Bowling Green May 17-19th??

P.

[tomtom72]

Just another vote for buying Marc's chip. It was the best money I spent on "extras" for my car and I'm sorry I waited so long! :mrgreen:


To your questions Manny:
1.) the system is working just fine, and the temps you're seeing are quite normal with the factory fan programming!

2.) Using a lower opening T-stat will not get you anything big unless you change the fan programming. I use the stock OEM stat and Marc's chip and the result is just fine!

:cheers:
Tom

[Corbusa]

Great info.. Thanks ... you da man ...

[Migfly]

WOW thanks everyone for your inputs,

You know Paul, I think we have narrowed it then. My mechanical skills are non existant, but reading your post and doing some digging, I think this issue may go away once i get the AC converted and filled up. For now, the Ac when the car is first turned on, has one of its lights blinking on the panel. Could not determine a code, but we think that it just may need freon and since all function on the panel work, just not blowing cold, it is therefore believed to just be low. The system, however, has supposedly a built in safety measure that may prevent the car from having the two fan running, until the Ac is porperly serviced, hence the temps issues.
Should that not take care of the problem i will def. look into the chip to reprogram both fans. At least we a have a what if....should fix number 1 not do the trick.
Regarding May's event don't know. I will have to check closer to the dates, my work does not allow me to know the time off this far in advence, but glad you mentioned it, thanks.

Manny

[VetteMed]

WOW thanks everyone for your inputs,

You know Paul, I think we have narrowed it then. My mechanical skills are non existant, but reading your post and doing some digging, I think this issue may go away once i get the AC converted and filled up. For now, the Ac when the car is first turned on, has one of its lights blinking on the panel. Could not determine a code, but we think that it just may need freon and since all function on the panel work, just not blowing cold, it is therefore believed to just be low. The system, however, has supposedly a built in safety measure that may prevent the car from having the two fan running, until the Ac is porperly serviced, hence the temps issues.
Should that not take care of the problem i will def. look into the chip to reprogram both fans. At least we a have a what if....should fix number 1 not do the trick.
Regarding May's event don't know. I will have to check closer to the dates, my work does not allow me to know the time off this far in advence, but glad you mentioned it, thanks.

Manny

Manny, if you are interested, I live about an hour and a half from you, I have some AC equipment, including a jug of R12, and I'd be happy to walk you through some of the common LT5 maintenance issues anytime, if you feel like making the drive.

Andrew

[tomtom72]

This is a fwiw on the A/C low freon issue. On a 90 if the system is low it short cycles the compressor. If it gets low beyond some point that I don't have a gauge set reading for, both fans come on and stay on as long as the motor is running.

This is what my friend's 90 Z was doing until we found and fixed the leak and then charged the system properly. If you are sure the system is low on gas and the second fan isn't running I would check the 2* fan relay to make sure it's good. Again, this was on a 90 Z, and I don't know if this applies to any later year Z.:o

:cheers:
Tom