Sorry if this is a NOOB question, but I've searched the internet and my owners manual (inclusing FSM) and I haven't found what I consider a definitive answer.

I was poking around my vette today (92 LT1 6 speed) and I decided to check the coolant tank in the front right of the engine bay. I noticed it was pretty much empty, except for a very little bit at the bottom. I decided to look into if I needed to put more in, and how to go about doing that.

Turns out as the car is cold there should be very little coolant in that tank, but when the car is warm and up to speed there should be a lot of coolant in that tank? at the winsheild side of the engine bay is another coolant tank apparently and that's where the main reservoir resides.

Also, it says in the manual to add GM Engine Coolant Supplement (GM Part 3634621) with the coolant only if you are doing a complete coolant change.

That being said, is any GM certified Coolant alright? Or is there something more specific recommended when I do the coolant change? I know that I need to put it in through the Top reservoir (not the one that I noticed was almost empty), and that I need to follow the directions in the Manual very carefully. My question though is what kind of coolant is recommended, and where would I find this Supplement if it's indeed still needed?

Thanks!

 

If the coolant in the system is green, add 50-50 green coolant to the surge tank (top reservoir). AutoZone (and others) carry a coolant that can be mixed with any coolant.

The coolant overflow bottle has a cap that unscrews, and the cap has a measure device showing the level for hot and cold coolant.

Fill the overflow bottle by removing the cap (not from the surge tank, although overflow from the surge tank will end up in the overflow bottle).

If you checked the level of coolant in the overflow bottle, you had to remove the cap with the measure device attached. Does the coolant overflow have a cap? Sounds like you may need a cap:

 

I do have the cap pictured, and I also did remove it when the car was cold, and hot. Both times the coolant was down at the bottom which to me says I need to add coolant? The car doesn't overheat, the low coolant light isn't on, and I really have no troubles but I decided to look this afternoon at the coolant when I had the hood up and now am at this question...

So to top it off, I just need to add some of the add to anything to the overflow tank (the one at the front of the car)? Does it sound like I even need to top it off?

Thanks in advance!

 

If the surge tank (top rear of engine) is full, then your radiator is full. The surge tank is just an extension of the radiator.

The overflow bottle (lower front of engine) acts to catch expanded coolant as the engine heats. Coolant is siphoned back to the surge tank during engine cool-down. Definitely maintain the coolant level in the overflow bottle to the marks on the cap shaft. Note there are two coolant levels on the cap shaft: cold and hot. The coolant level shaft is akin to the oil dipstick.

Check the surge tank cap gasket for any deformation.... rips, tears, splits, etc...... that would allow outside air to enter the system. Any air leaks will negate the siphon during cool-down, and the radiator would be short of coolant.

The cap pressure rating should be 15# (replacement caps are usually 16#, which is OK). The cap must be designed for a 'closed' system. Most, if not all, caps produced within the last year, or so, are suitable for both 'closed' and 'open' coolant systems.

 

No deformations on the Surge Tank's cap or any other parts of the tank. The overflow tank is just empty whether the car is hot or cold. I take that statement above to mean that I just need to add some coolant tot he overflow while the engine is running and hot to run it to the HOT part of the dipstick.

Is checking the Surge tank as simple as removing the cap?

Thanks again!

 

Fill the overflow bottle to the 'cold' mark on the cap shaft. If you over fill a tad, no problem. Engine does not need to be running.

During your normal driving, expanded hot coolant will flow to the overflow bottle. Don't worry about the 'hot' mark. The 'hot' mark on the shaft is just an approximate level indicator..... not critical.

Yes, checking the surge tank is as simple as removing the cap, and noticing the coolant level, which should be full to the brim.
Do not remove the surge tank cap when the coolant is hot........ there is pressure in the coolant system until the engine cools.

 

You're the best Seabright, am going to go out and check this shortly. First though by chance, do you know what lights are supposed to come on in the information display (center console) when the car is started?

Most of mine come on, but the low coolant doesn't. Is it supposed to? I am wondering if I do indeed have low coolant about changing the bulbs. Is there a good step by step on doing that online?

Thanks!

 

If the level in the overflow tank does not rise when the engine is fully warmed up you have one or more problems.
If the cooling system is not full then the overflow tank will not rise when hot.
The tube leading to the bottom of the overflow tank could be clogged.
Either way, if the level does not rise in the overflow tank with the car hot then you need to find out why.

 

Low coolant light does not come on at start-up. The sensor for the 'low coolant' light is located in the bottom of the surge tank.
Very easy to replace, if necessary. No sensors in the overflow bottle

 

Didn't get a shot to do this yesterday when I went outside to do it. The wife needed something and I of course went to take care of her. I am planning on running home to check this at lunch though. I won't trap any air in the system if I open the surge cap will I? Or will I need to burp the System after I'm done?

Thanks!

 

[QUOTE=Photoguy000;1584176990]..... I won't trap any air in the system if I open the surge cap will I?

No air problem opening the surge tank cap WHEN IT IS COLD


Or will I need to burp the System after I'm done?

The LT1 engine is self-bleeding (although you will read about gigantic bubble horror stories). If you need to add coolant to the surge tank, fill it to the brim...... run the engine at idle, WITH THE SURGE TANK CAP OFF, until the tstat (thermostat) opens (about 8 minutes).....you may see the coolant level drop.....add more coolant as required........ replace surge tank cap..... done.


Just remember that the cooling system is a 'closed' system..... meaning:

With the engine block full, the radiator/surge tank full, and the overflow bottle at the proper mark when 'cold'...... as the engine
heats, it displaces expanded coolant into the overflow bottle. When the engine cools, it creates a siphon from the overflow bottle back to the surge tank. It is just a cycle that occurs every time you operate the vette.

When the vette is cold, and the surge tank is not full, and overflow bottle level is near the 'hot' level on the dipstick, then air has breached the system and no siphon has occurred. We need to correct that by checking hose ends for tightness & splits, damaged surge tank cap gasket, anything that would allow air to enter the system.

 

You won't trap any air in the system by simply removing the surge tank cap. The system is designed to automatically purge air from the surge tank, as long as the overflow tank has coolant for the system to draw back in as it cools down.

There are bleeder screws on the thermostat housing and another place (varies by year and engine, I think) and I feel it's a good idea to check these periodically and release any trapped air, usually it's not much but the system should not have any air in it. Do a search and you'll find info on the air bleeder screws. Be sure not to spill any liquids onto the optispark distributor.

 

Ok, so I did as directed.

I opened the surge cap and it was not filled to the brim. I added the 50/50 add to anything non dex cool stuff until it was brimming over the bottom of the hole at the top of the surge tank. I went a little higher but I could just see it draining out of the top so I stopped. I added about a pint.

I started the car with the surge lid off and let it run for approx. 12 minutes, or 195 degrees on the digital dash. The coolant level didn't drop, so I put the surge cap back on the. Way it came off except while the engine was running.

I then took the car out for a quick 15 minute trip down to the a nearby highway ramp, then brought the highway two miles back to the exit close to my house, then drove home in the city traffic. On the highway the car seemed happy in the 190s but in the city ranged from 201 to 206' which was what it was doing before.

Weather here in Indianapolis was 85 with around a 70% humidity. The temps weren't that unlike before, I apparently have enough coolant now

After the quick drive I checked the overflow tank and it seemed like the level had risen according to the dipstick, but not a ton. I figure it was because I wasn't really out for very long.

Does this all sound normal and good?

Thanks again you are all the best!

 

Perfect.........

 

You're the best Seabright.

Ran home for lunch and took the car to get gas. Did it to check the temp on yet another quick jaunt, but also to make sure my coolant wasn't all over the garage floor. Temp was in check and garage floor was still clean.

Not sure where the missing coolant went, but at least the new stuff is not leaking out anywhere!

Thanks again a Ton!

 

Glad we could help........next year we can do a coolant change

 

No one answered your question about the coolant change or the coolant supplement that the manual describes. I need to learn more about this supplement. GM part# 3634621

 

Mine does.