MsEllie

My 1984 Corvette runs way too warm in the city , as the fan does not come on until some stupid-high number, after which it goes into the 240's. Putting the air on helps as the puller then starts, but it just delays the inevitable run as hot as the sun. I need to add a front fan, and have seen some new tech on the web, here and there, like brushless, and having its own computer. Any thoughts?

1984Z51auto

When I had my '84 I added the stock early C4 pusher fan with a manual switch and relay, it worked well for daily driving in Colorado. I believe the "Y" bracket and fan setup for the pusher fan is still available from some suppliers. Make sure you really need the extra fan: if your radiator/condenser is clogged with trash that really fouls up airflow and cooling.

MikeP84

Have you thought about dropping the thermostat down to 180 then getting a 190 fan switch? If your temps continue to raise until it overheats then this may not help but if it raises to the 240s and stays there then this may help. I would also recommend checking for crap that may have built up in front of condenser or in between condenser and radiator.

WVZR-1

I don't believe 'add-on' fan should be the first consideration.

I believe you confirm the condition of the cooling system in it's entirety and that would start with a 'scan' of the ECM so that you can evaluate the temps that the ECM sees. Being an '84 I'd think it important to confirm the condition of the ECT and the connector for the ECM, since the '84 fan isn't ECM controlled you use the scanner to confirm the actual temps where the fan actually 'turns on'.

If you've no documented 'cooling system services' I'd think you go there next. Flush of the system and cleaning the condenser/radiator module and making sure the lower deflectors are present.

There isn't a simple solution - a new fan option behind the radiator shouldn't be ruled out.

Until evaluated I don't believe switches and thermostats deserve considerations.

A DIY evaluation isn't difficult for a talented person but if this needs to be a 'FOR HIRE' there's way more the OP could add to be better advised.

Much depends on previous maintenance.

billschroeder5842

As part of your diagnosis, make sure you look BETWEEN the radiator and condenser and clean out the accumulated stuff. You could spends zillions on new switches, fans thermostats etc, but if you are clogged up, nothing is going to work. Pop off the shroud and get after it with a vacuum cleaner.

Here is what I found after I brought home a C4 a couple of years ago and was doing my base line PM. I cleaned it out and the car dropped 15 degrees without spending a dime.

confab

My 85 does fine now, without the air dam or a second fan. A new radiator from Autozone (One of the cheap ones) and a lower temperature switch in the head, and it does perfect.

After all those years the radiator was full of sediment and probably stop leak and who knows what. Checking in front for debris (Like Bill S said) is important too. Don't forget under the car in front of the condenser, as they tend to "snorkle up" everything in their path. Fresh, Dex-Cool, antifreeze is about the best corrosion inhibiting coolant I think I've ever seen.

Just making sure what you have works well is probably the best place to start, because you can bet it didn't overheat like that when it was new.

Good luck!!

Cruisinfanatic

All you need to do is clean the radiator you have. You need to take it out to do it properly

MsEllie

System flushed, and rad and condenser as clean as the day it left the factory.

MsEllie

160 degree thermostat installed. It is too cool in my opinion, because tonight it would only get up to 150 on the way home from the city. When I run air, the fan automatically runs, and it can not keep up--in city traffic.

Tom400CFI

Well something else is wrong then. These guys are right. The C4 cooling system is WAY better, than good enough. There is no way your properly operating cooling system will allow temps into the 240˚'s in any kind of normal driving.

Flush it again. Or something. Figure out what the actual problem is, rather than "band-aid'ing" it with another fan.

But if you REALLY want another fan....I have one for sale, HERE that I'd be happy to sell ya.

MsEllie

Well, the system is in pretty good shape, as the car only has 17500 original miles on it. Flushed the system better than any for hire garage. Lower deflector is no good when you are sitting at a stop light. It cools just fine when you are under way. Water pump seems excellent. Rad and condenser are clean. I didn't know I could hook up my OBD1 reader and get a temp reading. I'll verify. What is an ECT?

MsEllie

Flushed with a good rad flush, then drained through the block until you could make tea with the water, fresh anti freeze, but I did not use Dex-Cool, as it was not invented back then. Prestone, I believe is what I used.

Tom400CFI

Sounds like the fan isn't turning on at the right temp, or at all...or your dash reading is off.

I have an OBD I scan tool that can do custom data stream, and display 8 sensors/actuators at a time. OTC Monitor 4000e, so yes, you can do that/they exist.

ECT = Engine Coolant Temp. WVZR-1 was rightly advising you to scrutinize the connector at the engine coolant temp sensor. It's a troublesome connector on the '84 MY engine.

FYI, or for reference, my '92 runs at about 185-195 or so, at speed -even on +100˚F days. Sitting, of course it'll run up to the ~230˚F "fan on" temp, it might hit 232˚F, then the fan draws the temps down to 217 where it shuts off. A/C on, it never gets above ~210 no matter what I'm doing. Even dual driving auto-x in 100˚F temps.

Your car should perform about the same.


.

MsEllie

Why did my 86 have 2 fans? And how does a car cool at a stop light unless the fan is willing to run? Did GM not make these run hot for emissions considerations? I will look at pulling the rad tomorrow. I will use compressed air from the inside out first to make sure there is something there. I'll have another look.

MsEllie

Seems to me that my scan tool has an out plug to hook into a laptop; maybe that would give you more info on a screen. The fan certainly turns on immediately when you turn the air on. We just topped it up tonight, and seemed to work flawlessly with the air on. It would be nice for the fan to turn on at 185-190 without resorting to turning on the air. I will check the connection in the morning.

Tom400CFI

I don't know. Mine has two, but only one ever runs.

Everyone says "GM made these run hot for emissions reasons". Maybe. The reality is "GM made them to run all over the place"...so we don't really know what or why GM was trying to accomplish. For example, the LT1 comes stock with a 180˚F stat. In practice, it can and does run down as low as ~175˚F when under way. Since the fans don't turn on until 230˚F, then it'll run up to that temp when sitting. GM spec'ed both those values and they're a whopping 55˚F spread! So where did GM "want" these running and why? We don't really know. But in practice, underway they should stay below 200, IMO, and sitting/traffic, anywhere between 185 or so and 230, depending on what the fan is doing.


Sounds like a plan. I'd pay special attention to what the fan is doing, too.

MsEllie

Now that you mention it, my fan, when it does come on, does shut off at that magical 217! At plus 230 with iron heads, I am concerned that I will crack something. I will absolutely verify the cleanliness of the cores and report back,

WVZR-1

Of course the lower deflector is of no value 'sitting still' but you only mentioned COOLING ISSUES.

ECT/CTS - Electronic Coolant Temp/Coolant Temp Sensor - Called either but when referenced ECT it's most frequently understood you're referencing a device for the ECM.

A 'reader' won't you need a full functioning scanner.

If in fact your coolant service was done prior to DexCool then it was done at least 22 years ago.

If your ECT/CTS (in manifold) is round and white with a 'twisted pair' BLK/YEL then the first change I'd think a newer quality ECT/CTS and connector. GM changed in '85 and offered the older like yours only when requested. If a car went to a dealer with possible issues it was changed to the newer then. ECT and connector came in a single box. With a 'scanner' you can evaluate your cluster temp gauge and also the cooling fan turn on temps. The

This is the older 'twisted pair' for white round and there was actually 2 types of this, this is the later I believe.





For a new ECT use these GM #'s either at a dealer or as a reference at your favorite auto parts store along with the appropriate connector.

GM# 25036979, 12146312 or 15326386

shazam74

84 owner here. I dropped in a new rad recently since the old one had a couple pin holes in it (74K on the original and had not had a proper flush prior to me getting it). With the new rad and a refreshed 195 thermostat in it, its running to about 227 and then the fan kicks in and brings is back to about 217/220 (live in central FL). It had a proper flush once the new rad went in. I've read that this is within the standard operating temps. I just wanted to give you an idea of where the system should be running in a like for like vett.

MsEllie

I took everyone's advice today and pulled the rad. Boy, did the factory ever put the lower auto trans cooler line on tight! Well! Your wonderfully talented Jim Neighbours of Gomer Pyle, USMC fame used to say, "Surprise, surprise, surprise!" The rad I thought was clean was in real need of a thorough cleaning. The condenser was dusty, and the rad was dusty and dirty. Some strong soapy cleaner on both, with lots of water, after a careful air pressure cleaning, and you can now read a newspaper through the rad. And I also took the opportunity to flush and back flush the rad (it was pretty clean after driving with rad flush for a few days) and the block once again. Satisfied. In addition, I just so happen to have had a Hyper Tech 190 degree fan ground in inventory We put on a pot of hot water, dug out the laser thermometer, and verified that it started to ground at 185, and the buzzer on the circuit tester went off at precisely 190. Tomorrow morning, a new 180 thermostat will replace the too-cool 160--whereupon I will take it into traffic and try it again. At least I don't have to run the air to get the fan to run now. I am expecting superior results next time out. Now, does Dexcool actually outperform standard green anti-freeze for heat rejection without eating my gaskets?