I bypassed my heater core last week since I haven't had the time to fix it. I know the core acts as a mini-radiator, so the overall coolant temperature is going to be slightly warmer.

The car comes to temperature from sitting all night in just 2-3 minutes of driving. It will keep inching up until the fan comes on or unless I get up to a fairly high speed (45+). Is my thermostat going out? I just had one put in maybe 10 months ago.

Speaking of fans, that brings me to my next point. My fan does not always come on at 222*, or whatever the stock setting is. Sometimes it will go all the way up to (240*?) the white line between 220* and 260* before it finally turns on. Do I need a new motor?

LASTLY, coolant disappears from the overflow tank at a very mild rate. There are no visible leaks and I can't smell anything burning.

I have 10 month-old heater and radiator hoses, so they should be fine. The hoses I used to bypass the core don't SEEM to be kinked...but if they were restricting coolant, I'm guessing that would cause the problem I'm experiencing?

I will put in a new core in the next couple weeks - but the car just seems to be running too hot. I don't want to lose my $4000 rebuilt engine! (I also heard rebuilt engines will run slightly warmer at first, from the mechanic who rebuilt it for me - is this true?)

Anyways, I'm just looking for some input.

As always, any replies are appreciated. You all have been a big help so far.

-Anthony Helton

 

Come on guys...NO thoughts whatsoever? I'm going on a 150 mile road trip in exactly 19 days, and it involves going up a mountain in what will probably be hot weather! I need this engine cool, and can't afford to have it taken to a shop

-Anthony Helton

 

Well I just had a recent problem with my car overheating and found out that a wire had fallen out of the fan switch so that's why the fan doesn't work so you might want to try that and you need to add more water to the system cause when your engine gets that hot, it takes all the water out and it evaporates so keep filling it up until it's all set.
Another thing is to see if the top radiator hose is bringing fluid from the engine to the radiator. How you do that is you turn your car on and give it a minute or so until it gets to your thermostat degree and then with a rag squeeze the top hose and see if you can feel the fluids going into the radiator. If it's not, then replace the water pump and if it is that means that the water pump is working.
The last thing I can think of is replacing the radiator or just flushing out the whole cooling system. Maybe there is some junk that is sticking inside and causing a back-up in the fluids.
Try those things and hopefully that might help you out.

 

Your heater core doesn't help cooling unless you have the heat turned on in the car(just like a radiator doesn't do any good without moving air). You can completely block the heater core hose if you wanted to. Get a better fan switch that kicks on sooner. If the temp seems OK above 45mph, the cooling system is working just fine. Below that speed, it's all about the fan. You just need a better and/or turning on sooner fan to keep the temp down.

"Come on guys...NO thoughts whatsoever? I'm going on a 150 mile road trip in exactly 19 days, and it involves going up a mountain in what will probably be hot weather! I need this engine cool, and can't afford to have it taken to a shop"
no whining on the message board Free help doesn't mean it will be quick or accurate, or exist at all

 

Yeah, re-reading my 2nd post, I realized it came off sounding a lot more whiny than I intended. :P

All help is appreciated!

-Anthony Helton

 

First thing to do when fan does not turn on all the time is replace BOTH fan relays. They are $16 or so, don't mess with them. Get the GM OE ones, not the chain store junk. Most causes of intermittent fan operation are traced to intermittent contacts in the relays or the relay connector. Over 45 mph or so the airdam provides the needed airflow to the rad. And yes, a rebuilt motor runs slightly warmer than one that has reached break-in but usually the temp difference from the guage is minescule.

 

If you're '85 is still got the stock single fan setup, as my IROC does, then simply wire up a switch to manually cut the fan on if you need it cooler for an upcoming trip.


Rebuilt engines do tend to run hotter from the extra friction going on inside the engine as metal pieces get used to each other...but this shouldn't effect the fan cut on temp.

Make sure the air dam is in place. Make sure you don't have a collapsed radiator hose ( happens only when warmed up, hose collapses in on itself ).

Make sure the thermostat is opening...verify this by taking off the radiator cap with the engine COLD and cranking the car...when you start seeing coolants flowing through the top hose freely, it's open.

Also, if you're using the factory gauge, might wanna borrow or install an aftermarket gauge to make sure the gauge is actually right....



HTH

 

Boy, can I relate to your problem. I've had overheating with my 82 Z-28 since the day I bought back in 84. It killed the original 305, but even after putting new motor, radiator, flex fan, water pump, etc. it still had the tendancy to run hot. Ive made headway on it though, by installing a plate on the water pump impeller, and putting a universal fit Griffin radiator that just fit with a little coaxing, and a 160 thermostat. I use a high performance flex in place of the original clutch fan arrangement that came from the factory. I'm seriously considering putting my AC back in next year. So far, it runs at about 180-200 depending on whether I'm stopped in traffic or not. As others have said, make sure you keep the air dam on the front, I put 4 aluminum brackets on to help keep it tipped to he front to scoop the air up into the radiator. Those are the things done thus far and it is much better, good luck.
Chet cc82z-28

 

hey I have experienced the same problem and my car was getting hot very quickly also, and i sent the rad to a radiator shop and they went through it and cleaned it out and was told that the rad was 40%clogged with sediment try having it cleaned at a rad shop.it now stays at 227 and wont move from there and i live in el paso tx so you know how hot it gets here good luck.

 

Well, what I'm going to end up doing is replacing the old dual core radiator with a 4 core radiator. That should solve all my problems. It wouldn't surprise me if the radiator does need to be cored out though.

-Anthony Helton