RonBrooksGA

I had my OptiSpark changed and with it a new water pump and thermostat at the same time. Now that I have the car back, I have a problem I have never had before. The engine temp is going high towards overheating when driving on the highway at constant speed. At idle even for 30 minutes it's fine. Driving around town it's fine. The only time the temp rises is if driven on highway at say a constant 65+mph. I've bled from the bleeder screw above the Opti as well as the bleeder on the throttle body. So I was thinking, what if the mechanic installed a non-LT1 thermostat that didn't have the "blanking plate" on the bottom to close off that internal passageway? Could that cause my issue?

Thank in advance!

Ron Brooks

PatternDayTrader

That's a good question. I don't really know since I've never installed the wrong one, but its really an easy job to remove it and inspect it. Maybe 20 minutes.

hcbph

Don't rule out the water pump or the engine being air locked. If the wrong pump was installed and especially if it's turning the wrong direction - that could cause overheating. If the engine is airlocked, again the engine could overheat as a result.

STL94LT1

Not possible on an LT1.

ex-x-fire

Running hot at highway speeds usually equals the radiator is blocked by debris.

bac22

Ask your mechanic for the part number they used with the thermostat. If the car is running hot then any responsible garage should look into the matter. And what temps are you hitting on the highway? Maybe the prior thermostat was rated too low as I've seen many people here on this forum install thermostats that open at lower temps. If anything the fact your not hitting temps running around town would seem more suspicious as less air flow is getting to the engine.

RonBrooksGA

On the highway the temps climb to 218-220 but around town or driving below 50mph I see 195. The thermostat was supposed to be a 180 degree. I will have to pull it to see if it's a correct design and check the temp it's rated for. I just hate doing ANYTHING near the damned Opti that involves liquid. The thought of coolant and rebleeding the system makes me nervous but there's no other way to be certain. I don't know if it's normal or not but my bleeder shoots directly back towards the engine block right over the Opti. I wish it shot forward. It's like the designer just wanted to make it more "interesting" every time you bleed the system!

bac22

Those temps are not what I would consider overheating, I routinely see 220 on my 96, although generally when in stop/go traffic. The electric fans will kick in at 220. Overheating would be more like 240.

markKlein

I agree, those temps are way inside intended temps. If I remember correctly, the fans actually don't come on until 228. 195 males perfect sense for a 180 thermostat ( 180 means it starts opening at 180, most thermostats aren't fully open until 10 or 15 degrees later, which means 195 should be about the minimum for a 180 stat). My guess is everything is working fine (as designed) and that it is a factory 180 stat.

AgentEran

I have had alot of success using garbage or grocery bags to cover the opti before doing work that involves coolant..

AgentEran

Check your radiator cap.. they get stuck sometimes and cause weird symptoms.

hcbph

And here I thought all C4 Vettes had a reverse rotation water pump. Learned something new.

Whaleman

https://www.ecklerscorvette.com/corv...1992-1996.html
I used this thermostat and it is very high quality.

RonBrooksGA

Great idea on the garbage bags! I will go with that and rags above them. I have a new and proper thermostat. Once I open up the and check the one that's installed I will report back but I am glad to hear that my temps are not completely alarming! I'm hoping that I remove the old one and see there's a tail with the blanking plate missing!

Whaleman: that's the brand I bought, so here's to hoping!

ctmccloskey

You have heard that road debris can cause issues as it likes to stay between the radiator and the condenser. Cleaning this area is "critical" for a cool running Corvette. The other place to look for trouble is under the front of your car. There is supposed to be an air dam under the front of these cars. Before you go the route of the thermostat try cleaning between the radiator and verify that the correct air Dam is down there. Just missing the air dam can cause a Corvette to run hotter on the highway but not in town.

Another thing to check is that your car does not have too much anti-freeze in it. Excessive anti-freeze can cause a hotter running engine, Anti-freeze is nowhere near as good as plain distilled water at transferring heat. I live in Virginia and I run only 30% anti-freeze, 70% distilled water, this mixture gives me the protection I need for this area where it does not freeze that very often. I am also a BIG believer in RED LINE Products "Water Wetter", this material is a surfactant and allows the water to transfer the heat from the metal more efficiently. In a normal situation you get little air bubbles on the inner surfaces of the metal parts of the engine. These little steam bubbles inhibit the heat transfer, by adding the Water Wetter you get rid of the bubbles and therefore more heat!

In your case it sounds like you probably have a blockage someplace keeping the air from getting through the radiator. Good Luck and be sure to tell us what you found that caused this situation. We are all here to "learn" and "share" what we know about these amazing cars! I wish you the very best of luck in sorting this out, I hope it is an easy fix for you in the long run!

RonBrooksGA

Well unfortunately the thermostat that was in the water pump was the correct design. I installed the new one anyway because, hey, who knows? I've bled and bled the system with the heat on full hot. I cleaned both the condenser and radiator with the a they use on outdoor home ac compressors. The cooling fins pick up all kinds of dirt so you spray it on and let it set then hose off gently. I also used my air compressor to blow from the rear towards the front first. I didn't see any large debris but it's definitely all cleaned out now. I will go for a drive later today and see if anything has been accomplished.

RonBrooksGA

I just came back from a 25mi drive and its 78 right now. The highest the temp goes now is 210. From what everyone has said that's not a high temp to worry about. When driving 50mph or under or at a stop the temp drops to about 185. Still seems odd to me but I'm not quite sure what else there is for me to do at this point. The water pump is new. I bled the heck out of the system. I'm not getting any air more out. The thermostat is new and now I have cleaned the condenser and the radiator. I'm OK with 210 being the max temp but will have to see tomorrow in the heat of the day if that stays as the high number, but temps dropping while going slow or at a stop just seems weird and wrong.

ex-x-fire

To maintain highway speeds you have to make more horsepower, making hp makes more heat. You should see the fans they have for chassis dynos. I would have a look between the rad & the a/c condenser, because your temp at speed is still a little high.

Mr. Peabody

Perhaps reading this will ease your mind a bit. Your temps are not "hot" for an LT1

https://www.corvetteforum.com/forums...peratures.html

When you get to #1 read it out loud

RonBrooksGA

I read #1 and the info on that post is great! If it's not a sticky it should be!