A couple of days ago the low coolant level light came on my 94 came on right before I got home, no overheating. I checked levels in my overflow and they were fine. Today I made a couple of mile drive into town and then back home. right before I made it home I noticed I had a temp of 257. I cranked the heat and coasted into my driveway and then in my shop. I smelled coolant and after taking a look I noticed the passenger side plastic radiator tank had a split in it and made a mess of things. My question is I know I now need a radiator but is my problem that the radiator went bad or did something else go bad to split my radiator. What kind of things should I look at. I was planning on replacing my thermostat with a cooler one, now seems like a good time. BTW my water pump was replaced less than 3k ago. What should my plan of action be? Any advice would be great, it makes me sick my baby is broke and I want to fix it right. Thanks for your help

 

Sounds to me like it just quit. I had the same problem several months back and replaced mine. All's well now.

 

Wow, good catch, glad it didn't get to 'overheat' temps...

Regarding the 'low coolant' level light, that 'switch' is mounted in the bottom of the 'surge' tank (black pressure tank near windshield).

You mentioned initially checking level in 'overflow' (plastic tank near bumper) -- iunfortunately, when a leak develops, this IS NOT the ONLY place that should be checked.

Often when a leak develops in the coolant system, it prevents the cooling effect 'vacume' build-up in the system. Normally, this 'vacume' is what is necessary to allow coolant to be 'sucked' back into the 'surge' tank from the 'overflow' tank. Therefore, when there is a leak, frequently the 'overflow' tank will be full, yet the coolant is low in the engine/radiator/surge tank/etc.

Regarding the split radiator tank -- the radiator cap (on the 'surge' tank) 'protects' against excess pressure (which could split a radiator) by allowing it to escape into the 'overflow' tank when the pressure exceeds the cap's rated pressure..

Assuming the cap is functioning correctly (sugest having it tested or just replaced), it couldn't be pressure which split the radiator (btw, there is confusing info out there for the correct cap, so be careful and sugest only ACDelco brand (RC27?), many have had problems with aftermarket brands -- e.g. stant).

So, likely your slight overheating was caused by both a lack of coolant (leaking from split) and loss of pressure (which normally elevates the boiling point of the coolant) and was occuring even before the 'low coolant level' light came on.

Regarding the thermostat, remember that thermostats only control the minimum temps, its the radiator and water pump which control the maximum temps. Also, changing the thermostat temp without also altering the fan on/off temps can be ineffective at altering the typical engine temps. Further, LT1's are designed to run hot, its actually better for the engine than running cool, so most will recommend NOT changing the thermostat temp and staying with an OEM thermostat (e.g. ACDelco 131-100).

While you have the radiator out (presume your doing it yourself), suggest planning some extra time to clean the A/C condensor, there are lots of posts on ways to do this, but suffice it to say that if not cleaned, it will continue to block the air from getting to your nice new radiator.

Presume you also know the 94 takes normal 'green' anti-freeze (ethylene glycol with low silicates). Its getting harder to find this, so suggest Zylex or Texaco (avoid prestone's 'compatible with all', it's actually same chemicals as Dexcool -- with all the problems thereof).

 

Thank you for taking the time to give such an informative reply, I really appreciate it! When I buy my new radiator I have already noticed there are two basic options. Alum core with plastic tanks and all alum core and alum tanks. Is it worth it to buy an all aluminum radiator or just stick to the same design as an OEM. One other question. When I was checking the coolant level I tried to remove the cap on the upper resevoir and could not get it off. Is there a trick to it, I tried to remove it like a normal cap and could not remove it completely, I was able to turn it 90 deg but could not get it turn any more even when pushing down on it. If it is like a normal cap than I will mess with it again and figure it out, I may have just given up too quickly before.

 

Here is the cheapest AC Delco original replacement radiator you will find, the same as what came in your car new. There good people to deal with also...WW

http://cgi.ebay.com/ebaymotors/90-91...Q5fAccessories

 

Your very welcome, my pleasure.

I'd recommend the same OEM plastic tank radiator -- it's sure to fit, and given the old one lasted 15 years, why 'fix' something that isn't 'broken' -- so to speak..

regarding the cap, it is normal (press down 2nd time to untwist), but it also sounds like the wrong one is installed (I was correct in my previous post as I just looked at our 94, it is supose to be a ACDelco RC27 - 15 PSI). Just be careful, as the 'surge' tank is also plastic...

Once you get it off, recommend replacing it with an ACdelco as if it is that difficult to remove, it may have NOT let out the pressure and contributed to your cracked tank (i.e. the depth or spring tension may be too deep or too strong so it would NOT release pressure above 15 PSI to the overflow tank).

Another way to tell if the cap is not working is did the 'overflow' tank (by bumper) level ever increase? If not, when the cap is untwisted to the 1st stop (if hot), it should release pressure/coolant to the 'overflow' tank, did it? If no to both, then likey it is the WRONG cap, so replace it..

Also, I always wipe a small dab of silicone grease all the way around on the upper-most rubber gasket (the one that contacts the top of the 'surge' tank) to make subsequent removal easy..

 

Well, I finally got the new radiator (Delphi) in and all seems fixed. I just took a 60 mile drive and never got above 211 in town and around 205 on the highway. One nice benefit of this radiator change was the thorough cleaning my condenser got while the radiator was out. This made a huge difference in my AC temp. Thank you 94Admiral for the detailed advice, it was all good and very much appreciated. It feels good to be back on the road again. I think I am ready for my trip to Eureka Springs Arkansas Corvette weekend this OCT 1-3 now. Anybody else making the trip from here? We will have a convoy of 4 cars going, A mint 82 C3, 89 C4, 06 C6 Z06, and my 94 C4. Wichita to Eureka, I have dreamed of this trip for a long time.

 

Can you get an AC Delco radiator cap with pressure relief valve for an 89? I can only find a regular one.

Anyways, watch out on eBay sometimes. There is some jackass on there that sells used radiator and throttle body hoses that cost more than getting a new one. He had a USED Napa throttle body hose for $10 plus $6 shipping. I told him you can get a new OEM throttle body hose for $11 at the dealer. And if you got a new one at Napa, it would be cheaper than that.

He didn't really like that and was going on about how he sells alot of parts, etc. and that he would be willing to meet me somewhere. For what I don't know. Haha. I think his name was Redneck something or another.

 

I believe that he is selling used OEM parts for those that have to have original parts. I've gotten some pretty good deals from him in the past.
An ECM for 50 bucks and a few other hard to find parts.

The OP needs a good radiator and to buy new is best at this point.
Look up "corvette radiator 3 row" on ebay and find someone with a long selling history. These are better than stock, but not as good as DeWitts

 

The ones I commented to him were used "Napa" hoses. The price was more than a brand new one from Napa, then you'd have to add shipping. So, his used Napa hose was double the price of a new Napa hose.

I wouldn't buy a used radiator hose period and especially I wouldn't pay more than new.

http://cgi.ebay.com/ebaymotors/1985-...Q5fAccessories

http://cgi.ebay.com/ebaymotors/1985-...Q5fAccessories

The second one looks like a used OEM hose. Though, why would someone want to pay $9.99 plus $6 shipping for a used hose when you can get it brand new from the dealer for $11?