Z28_1991_Camaro

I've had an overheating problem with my car for quite some time now.
I did a 305 to 350 swap a few years back and it seemed like the problems just got worse then. I had problems only on really hot days before the swap, now i have them more frequently.
The temp gauge basically just keeps rising and doesnt stop. If I am driving on the highway im going fast enough that the air dam works and the engine will cool down to where it should be but if I was just sitting there or driving slowly it would keep climbing.
I checked the temp of the thermostat housing and it's reading nearly the same as the gauge in my dash so it's giving me a fairly accurate number.
Both of my fans work...one of them is on at all times. There is no air in the system.
I have since upgraded to a 3 row aluminum rad but it still runs hot. I didn't have a thermostat installed for a real long time because it ran much cooler without one. Yesterday I installed a new stat, thats the 1st time one has been installed with the new rad. The engine is still running hotter then it should but it seemed to peak and not keep climbing so I guess thats some progress.
The system was flushed several times, the hoses are new or in good shape. The only thing cooling related that i can think of that has not been replaced within the last year or two is the water pump. I took some temperature readings on my rad last year and posted them on here and someone said based on my numbers that my water pump was working.
When I squeeze the upper rad hose there is very little resistance. Should it be easy to squeeze it or should there be some resistance in there? (The thermostat was open when I checked)
I would think there should be more resistance in there but I'm not sure?

Anyone have any ideas or suggestions?

Is a water pump the next step?

JamesC

iTrader: (5)

The lower radiator hose often has a spring in it to keep the hose from collapsing when the car is hot. Might be worth a peek.

JamesC

the solitaire

Well, if the car is running and the thermostat is open the hose should be hot, and have some resistance.

If it's not giving any resistance it doesn't hold coolant.

As JamesC already pointed out, the lower hose can collaps as soon as the waterpump starts sucking coolant through the radiator. This risk does not apply for the upper hose, which receives the pressure from the waterpump.

If the lower hose collapses, the amount of coolant transported reduces significantly. Either that or the waterpump isn't promoting coolant through the system.

Easiest way to check however is to let the car run, starting with a cool engine to prevent the pressure buildup dumping the radiator contents when you open the cap, and wait untill the thermostat opens. As soon as it does, you should see a significant amount of coolant flow through the radiator.

If coolant does flow strongly, try and find someone with a WinALDL and connector to see if the car runs lean.

TTOP350

iTrader: (8)

sounds like a low speed air flow problem.
Make sure your fan speed is up to snuff. These do wearout over time and turn slower than they should. maybe you need replacement motors..

Z28_1991_Camaro

I replaced the lower rad hose when I installed the new rad so I don't think that is the problem...it did have a spring inside of it.
The fans are both brand new, the rad came with 2 new fans as well.
The upper rad hose was hot to touch but like i said there was minimal resistance, I could easily squeeze it.
I'm not going to have a chance to touch the car until Thursday so I'll look to see what the coolant flow looks like. From what I remember, the rad was full of coolant so you couldnt really see what kinda flow it had but I'll look again Thursday.

Are winaldl expensive? I don't know anybody that would have one.

Z28_1991_Camaro

I looked in the rad when the thermostat opened and it appears as though the coolant is flowing but I don't know exactly what it should look like.

The outside temperature was not too hot tonight so I drove the car to my parents house and unless I was driving on the highway the temp gauge just kept inching closer and closer to the red zone. On the highway it stabilized around 240 degrees. If my memory is correct, when I didn't have the thermostat installed it ran somewhere between 180 and 200 degrees on the highway.

Do I try a new water pump? Autozone and Advance auto sell them for less than $30. Advance carries an Edelbrock performance water pump for $200, should I consider that?

UnderCover89TBI

iTrader: (25)

air dam and baffle are all there correct? what temp thermostat did you install? what brand was it? I do not trust any thermostats that Oreilly/autozone/advance sell unless it was stant, or if you purchased a high flow one from like Mr. gasket, milodon etc...if it runs cooler w/o a thermostat I wouldnt run one then. Are both of your fans turning on or just one? that'd be a problem.

Z28_1991_Camaro

The air dam and baffle are there.
I installed a high flow Summit OEM thermostat. Someone on this forum told me not to use the lower temp ones as the computer and everything is designed to run at a certain temp.
Both fans work. One is on at all times, the other comes on once it hits a certain temperature.
The fans are supposed to be blowing away from the rad right? The one that is on at all times blows away from the rad. I'm assuming the other one does as well but I will check to be certain

UnderCover89TBI

iTrader: (25)

yes they are called puller fans. As they pull the air thru the radiator. and I ran a 195 on a stock tune, with my performance chip I run a 180.

Z28_1991_Camaro

Does the fact that the engine runs cooler without a thermostat indicate poor coolant flow/pressure?

Should I try and change the water pump for only $30?
I'm all out of ideas. The water pump is probably at least 5 or 6 years old by now.

antoine

Check the timing I had one that was retard way down and it made the camaro run hot

Z28_1991_Camaro

The timing is set properly so thats not it

UnderCover89TBI

iTrader: (25)

usually you can check water pump flow by having radiator cap off and goosing the engine a little bit. you should see the coolant in the radiator get sucked down.

Z28_1991_Camaro

I took my thermostat back out yesterday and the temp never got higer than around 200 degrees when I drove it.
The car is basically not driveable with the thermostat in.
I looked in the rad and gave her some gas and there was definately some activity in the rad. The coolant didn't really get sucked down but it was definately flowing faster.

It doesn't make sense to me that it will work ok without the thermostat but not with it?

The car is designed to have a thermostat so why can't I have one in there without the over heating?

JOHNNYZ28

i have the exact same situation in my 91 z 28 as you do only thing i have not changed is my water pump also and when i bought it the thermostat was out i put in a stock one and had the radiator redone new hoses 305 to 350 swap my car runs fine unless the a/c is on and it is hot out it will rise to 240 then if i turn the a/c off it cools down fans work fine and when i pull in some where it starts to percualte in the coolant tank wish i could fix it i love the car

CamaroKidAndy

May not solve the whole thing but have you changed the radiator cap? If the cap is leaking (they do wear out) you won't be getting enough pressure thru the system to maintain the cooler temp. Signs of this can be the temp rising when you stomp down on it and especially taking a long time to return to a normal tempature range. Yes, your water pump can be a problem, and is a reasonable cost repair. Another area that may be a cause is a bearing going bad on your a/c compressor or other accesory on the belt, including the tensioner. Start with the simplest and work to the more difficult.

JOHNNYZ28

WELL I WANT TO THANK YOU VERY MUCH YOU MIGHT HAVE STARTED TO LEAD MEAD ON THE RIGHT TRACK I REPALCED THE RADIATOR CAP TODAY AND THAT WAS NOT THE PROBLEM ALSO I CHECK THE LOWER RADIATOR HOSE FROM WHAT I CAN SEE DOES NOT COLAPSE IN WHEN THE CAR IS UNDER HARD THROTTLE BUT IT DOES NOT HAVE A SPRING IN IT I TRIED TO BUY A LOWER RADIATOR HOSE TODAY WITH A SPRING IN IT WITH NO LUCK AND THE CAR DOES HAVE THE PROBLEM YOU SUGGEST WHERE UNDER HARD ACCELERATION IT HEATS UP REAL QUICK AND DOES NOT COOL DOWN I OPEN THE CAP AND LOOKED AT THE FLO I DO NOT SEE WATER FLOWING THROUGHT THE RADIATOR I SEE IT FLOWING THROUGH THE HEATER CORE HOSE THAT ATTACHES TO THE RADIATOR NEAR THE FILLER NECK FAST FAST MOVING WATER COMES THROUGHT THAT SMALL 5/8'S HOSE WHEN I REV THE CAR ANY SUGGESTIONS FROM HEAR PLEASE AND THANK YOU

JOHNNYZ28

ANOTHER THING I NOTICED IS WHEN THE CAR IS HOT IT PERCULATES IN THE COOLANT TANK AND WHEN I SQUEEZ THE RADIATOR HOSE UPPER ITS HARD BUT WHEN IT COOLS A BIT I CAN SQUEEZE THE HOSE I HEAR AIR IS THAT NORMAL

MoJoe

iTrader: (5)

Do you have the correct water pump? Your '91 accessories should be serpentine belt, which spins the pump opposite direction as the older "standard" belt system does. If you swapped engines with a standard rotation pump and are using your serpentine belt system, you are spinning the pump backwards.
Cost: new water pump.
BTW, I am not sure how to identify one vs the other.

CamaroKidAndy

Agree with the above posting. If the water pump doesn't solve the problem it may be a head gasket leaking.

RJ76FLORES76

I am having a very similar problem with my 91 Z28 TPI 5.7L I just bought a new 3 row aluminum radiator and in the process of ordering silicone radiator hoses, high flow water pump and thermostat(not sure to get 160 or 180). my concern now is that the water in the rad and water pump that I removed today was filthy. it looked dark colored, not sure what to think of that. any ideas?

NowhereFast

Could just be the inside of the block rusting. Oil from a head gasket leak wouldn't mix, you would see them separate in the container you put the coolant in.

plum92_camaro

Are the fins of the radiator clean? and the condenser too? Make sure they are clean allowing maximum air flow.

I had a overheating issue a few years ago like yours. I did so many things at once I can't tell you what it was. I pulled the radiator and condenser and cleaned the fins/coils, changed the radiator hoses, new thermostat, and had a shop flush it with a machine. Never overheated again.

Good luck!

RJ76FLORES76

I was thinking the same thing. it is super dark rust colored

RJ76FLORES76

that's what I am doing too, I just bought that all aluminum radiator that I mentioned above. I am going to install all hoses new, upper and lower silicone. water pump and thermostat high flow. replace overflow bottle it looks nasty still open for advise and suggestions though

Z28_1991_Camaro

I am the original poster of this thread. Just this past spring I finally figured out what was causing my problem. It was the fans, although I had brand new fans that came with my new rad, they simply weren't moving enough air. I purchased some new fans and for the first time in about 5 or 6 years I actually saw the temperature gauge go down while idling.
I have since put a thermostat back in and I re-wired my fans correctly so that rather then the one fan being on at all times, now they both come on at the original temps that GM intended them to.
I also drilled a few holes in the thermostat so that there is always some coolant flowing. The car always ran cooler without a thermostat so this I'm sure helps a little.
I've had no overheating problems since even with my a/c on regardless of the outside temperature.

I did have a bit of a wtf moment however, as once I put the thermostat back in, the temp gauge was reading as though it was almost in the red zone. Turns out my temp gauge on the dash is no longer accurate. My infrared thermometer no longer matches what my dash says, but when the fans came on, the thermostat housing temps were the correct temps that the fans were supposed to come on at.
It definitely made me uncomfortable seeing the temp gauge on the dash reading so high especially considering the overheating issues I've had.

I hope you solve your problem faster then I did

RJ76FLORES76

thank you for the response z28 I definitely want to get rid of this problem in my car and I cant move on to other projects I want to do to it until this is resolved.
also on the same note yesterday I removed the old rad and water in it was really dark, any idea why?

BrutalGTA

iTrader: (2)

When was it last replaced? For $30, I'd buy the Airtex and give it a shot.

RJ76FLORES76

Replaced radiator, it had 3 plugged rows