I have a 91 z28 5.7L.

I did a 305 to 350 swap a few years back. Prior to the swap I never had any overheating issues that I can recall.

Now days however, if it's a hot day outside the car will overheat while idling or driving slower than 70 or 80km/h. If the car is idling the temp gauge rises and would eventually get into the red zone. If the air conditioning is on this process happens only in a much faster fashion.

I dont have a thermostat installed and both of my fans work. One is rigged up to run all the time and the other comes on I think around 220 degrees.

I'd have more piece of mind if I could get my car to run cooler.

I'm thinking maybe a new radiator is the way to go? I found one on ebay:

http://cgi.ebay.com/ebaymotors/3-Row...Q5fAccessories

or for another $180 more I can get it with new fans as well:

http://cgi.ebay.com/ebaymotors/3-Row...Q5fAccessories

Would a new rad solve my problems? If not what else would I have to do to get my car running cooler?

 

flush your radiator first, then when you fill it up go to your local parts store and get WATER WETTER put that in there, if it still over heats still its prolly just your temp gauge if you have a fan running at all times and your radiator isnt clogged, but if its clogged, replace it if when you flush it it seems to have flow, then its probably just the temp gauge mine is retarded and gives me all kinds of BS Readings

 

I don't think it's the temp gauge just based on it's readings it seems to make sense. For instance if I'm in stop and go traffic for a while and then I jump on the highway it cools down quite a bit once im cruising for a few mins.

I will attempt to flush the radiator this weekend and see if that makes a difference.

Assuming that flushing the rad doens't help and that my temp gauge is working properly, would a new rad solve my issue?
Any thoughts on the 2 rads in the links above? Do they seem like they are good quality and should I go for the fans or stick with my stock fans if I do end up purchasing the rad?

 

i bigger or aluminum radiator will cool more coolant and cool it faster, in turn, cooling your engine

 

Ok, this is more of a question than a statement.

Isn't it true that if you run witout a thermostat that the coolant moves through the radiator faster than it can be cooled. I wonder if one of these would help,... http://www.summitracing.com/parts/CTR-80-150/

 

The "remove the thermostat"/"need a restrictor" issue has been
around since the model T, with desciples of both arguments.

HOWEVER
With the advent of ECM systems that are VERY dependent on
operating temperature, it is HIGHLY advisable not to randomly
tinker w/ thermostats, sensor switches, etc., without a good
deal of experience that can propagate the changes through the
control system. (This is not to say that GM's temp. controls
are ideal, but that changing them needs to be done carefully.)

That being said,
Z28, its not clear if this has been going on SINCE the swap,
or is just recently manifesting itself. If recently, than some
components are failing. Rad flush is an obvious & easy first
step. Water pumps usually fail by leaking. To fail circulation,
the impellor must not turn, or have lost blade structure to corrosion.
Check the main hoses. If they are collapsing at any time (can't
remember if its reving up or down...), than the internal wire bracing
is weakened, and the hose should be replaced.

Good luck, hope this helps.

 

http://www.superchevy.com/tech/0502s...ing/index.html

 

That link that transam posted described my problem spot on.

I ordered a new 3 row aluminum radiator today.

Now that I think about it, back when I was using a thermostat I had this overheating issue that im having kinda come up out of no where. Because I remember my car running hot so I changed the thermostat to a lower temp one and I still had the overheating issue. That is why I decided to just remove it completely. The problem with the thermostats installed was the car got up to temperature way too quickly. Now it takes quite a bit longer for the car to get to temp without the thermostat.

When I get the new rad installed should I try running the car without the thermostat and see how it is or do you think it would be wise to just put one back in?

 

How did this turn out ?

 

I just found out today that they are out of stock on the rads so it's going to be another couple weeks before I get it

 

It may be too late, but you should really check your coolant temps before spending a wad of cash unnecessarily. Leave the radiator cap off, start and run the car, and stick a candy thermometer ($5 from walmart) in the top of the radiator and see if the thermometer matches the guage temps as the temp rises. A new temp sensor is only $20 or so.

I just hate to see you throw $300 at a $20 problem - so many folks on here jump the gun and opt for an expensive band-aid instead of really diagnosing the problem. If I had all the money spent on mis-diagnosed issues I've seen on this board, I'd have a warehouse full of perfectly restored classics LOL!

 

At the same rate, if he still has the stock radiator, that thing is begging to be replaced with an aluminum radiator. He could have rust and junk flowing through his system. I'd look at it as an upgrade rather than a fix.

 

The way I see it, it wouldn't be a bad thing to upgrade the rad. The current rad is the original so its almost 20 years old.

Yes, maybe it's possible that my temp sensor is faulty but I would feel more comefortable knowing I'm going to have a new rad that will do a much better cooling job.

I don't think the temp sensor is faulty however. The gauge makes sense when it gets hot and cools down. I think if the sensor wasn't working properly, I would get high temp readings even when it's not 80-90 degrees outside. I don't know the exact temperature it needs to be outside but when its a cool or even a warm day there is no overheating issues whatsoever. It's only when it gets above the 80-90 degree weather that there are issues.

 

Air Dam(s) intact?

Jim.

 

The air dam is intact.
The fact that there is no overheating when I'm cruising leads me to believe the air dam is doing it's job properly.

The rad I ordered is finally back in stock and was shipped yesterday. I'm hoping it arrives before next weekend. I'll keep you all updated after the install.

 

i agree. the ecm needs the imput from the stat and it needs to run at 190 not the 160's that you can find as aftermarket.

the coolant cannot be circulating without stopping or it never cools and i dont care what you radiator is made of.

 

Last year's project was cooling, so first I did two rad flushes, changed the thermostat from a 192* to a fail safe 160*, installed A Hypertech #4026 Cool fan switch, (turns on primary fan at 177* and off at 166*), And also rewired the secondary fan (A/C fan) to manual switch from inside the car. I refilled with 50/50 mix using distilled water and added Water Wetter into rad. My car never sees above 180ish......in southern ontario,.....(stock duel electric fans and rad). But i've been told that you DO NEED a thermostat for proper cooling, the hot coolent needs to sit for a few mins to cool down before going back inside engine, free flowing coolent will never cool down as much, as quickly then without thermo...

 

hey i dont mean to thread jack here, but im wondering if it is time for me to get a new radiator. my car seems to overheat with any driving unless its highway cruising. i have a digital dash and it will go to the red with about 15-20 min of city driving. i look at the coolant and there is almost like a muddy color that is with my green tint. im wondering if this is rust and if it is is getting a rad a must do or i can survive a little longer.
thanks

 

its very likely it could be the coolant sending unit. mine reads 20 degrees hotter than actual temp. although the fact it moves up and down with the temp just shows that its still reading hot and cold, but not how accurate it is. i would clean your cooling system, and check your hoses. especially the bottom one which may collapse if the spring inside has gone bad. also have the system pressure checked at any shop and the cap aswell. the fact you have 2 fans and no thermostat is alittle suspicious that your overheating. id say also check infront of your radiator for any bags, or random crap that can get stuck in front, obstructing air flow. also +1 for that water wetter. its good stuff.

 

87-TA-GTA, start with a FEW rad flushes FIRST.... Sounds like you got some old coolent in there, coolent doesn't last forever (2-5 years) depending on how much you drive your car. Besides, a rad flush is easy and cheap to do. Then refill with a 50/50 mix (using distilled water), and add a bottle of Water Wetter, its cheap.

Why Distilled water?.....its basically 100% pure water not like the crap that comes from the kitchen tap....much better for your cooling system.

 

Here is the latest and greatest...

I got my new rad this past Monday. I flushed my system 3 times on Wednesday before I put the new rad in. I put the new rad in only to find it didn't fit in the rubber mounts properly so it sat too high. The rad is supposed to a direct replacement. I know nothing is ever a direct replacement but I was optimistic this time around only because of the auction listing. They have a guarantee that if the rad doesn't fit they will refund you including shipping costs. I called the manufacturer and he suggested I try and move the rubber mounts or to cut them down a bit. So on Friday, I spent several hours modifying the rubber mounts and just getting the rad to fit in the car. I managed to get it in decently, not a perfect fit but it was good enough. I didn't have any anti-freeze left over because Wednesday night I had to put the new bottle back in the old rad because I needed my car on Thursday. I was busy on Saturday and never had a chance to work on my car at all. Yesterday, I went and bought another jug of anti-freeze and filled up the new rad. My car wouldnt start because my battery was dead. So I went and bought a new battery and started the car up. It was running for a couple mins when I noticed the transmission lines were leaking. I thought I must have cross threaded the hole but that wasnt it. The hole for the transmission line is probably about 1/4" deeper on the new rad so the stock fitting on the transmission line is too short to seal the hole properly. I went to a local part store to see if there was any kind of adaptor I could find but they didn't have anything.
So I was forced to put my old rad back in again. I also put a thermostat back in the car. So now I'm right back to square one, the car runs much hotter than I like.
It definately ran cooler without the thermostat installed.

 

Aw man, now the mounts are different. i think if you really want that radiator in there, you can do a little hack job like i did. i bought a prefabbed brake line. i found the right size flare nut thing and bought a coupler brass, and a tube bender. its kinda hard but doable. then you just connect the new tube flare/nut to the radiator, bend the tube to the existing one, and use the coupler. If you need new radiator mounts you can pick them up at the stealership. Some dudes in here do that just to add another transmission cooler or extra filter. Transmission line isnt high pressure like a powersteering cooler or the brakelines (i dont mess the brakes) good luck man.. i hate changing radiators. i have to change mine twice in the last 4 years. and then i striper the flare nut, dang, then i did that on thing with the coupler until i add a cooler.

 

Keep the new rad. Try replacing the tranny line with new one's with the proper sized nuts on them.

 

I had the exact same problem your having.. i wired my fan to run at all times that the key is on.. my temp sits at 180 never moves never had a problem with it in the last 4 years

 

If you still have the stock radiator, i'd recommend a 3 row aluminium upgrade. You will need to upgrade your radiator eventually (as they did not come with aluminum radiators and are bound to rust eventually) . Consider it an upgrade