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I have a 81 auto with aircon and stock 350. I took the car in about 3 years ago to get a new exhaust they put new extractors on it but needed a smaller starter and broke apart of the water pump so they installed a new one. Ever since then it has been overheating. I got it home and flushed the coolant and it was very muddy and dirty since then it has been flushed close to a dozen time and is coming out clean. I have also replaced upper and lower water pipes the water pump was the wrong one they modified the shaft on the old one so it has another new one and fan clutch. I have replaced thermostat housing and thermostat to the lower 160 Deg, installed alu radiator and added new radiator foam kit. In traffic it is fine it only over heats on the hwy or going up hills. I am out of ideas, I have taken it to radiator shops and mechanics and they can't seem figure it out.
Squeeze the lower radiator hose. I bet you are missing the internal spring which is there to keep it from collapsing. Without it, the lower radiator hose can suck shut when the engine is running at RPMs higher than idle.
Overheating at idle: air flow
Overheating on the highway: water flow
First thing is to verify if its truely overheating, are you verifying the temp with an IR gun or just the dash gauge? What is the actual temp when its overheating? Seems that the shop don't know a lot about Vette water pumps, did they fit one with the correct rotation direction? Is the fan fitted the correct way. Guy had a Camaro here that kept overheating turned out the mechanic fitted the fan the wrong way round so it was pushing air towards the rad instead of drawing it away.
Squeeze the lower radiator hose. I bet you are missing the internal spring which is there to keep it from collapsing. Without it, the lower radiator hose can suck shut when the engine is running at RPMs higher than idle.
Overheating at idle: air flow
Overheating on the highway: water flow
Neither the new or old hose had the spring and I wasn't able to find one when I went looking for the replacement. I thought maybe if theis was the issue if the old hose may have failed after it was moved for the new pump as it was fine before then the new should be OK atleast for a small amount of time. I even thought maybe there was a spring I could put in myself but have not looked in to it to far.
Is the front "lip" spoiler up underneath in the front?
What temp is it getting to?
I am not sure about the spoiler Ill see if I can go look and take pictures. Unless its something the first mechanic removed and binned then I thought it would be strage for it to have caused it but Ill def try and look.
The temp I am not 100% Ill try and find a IR temp gauge but you can smell that its not right and the heat radiates really strong.
Jebby
Originally Posted by Haggisbash
First thing is to verify if its truely overheating, are you verifying the temp with an IR gun or just the dash gauge? What is the actual temp when its overheating? Seems that the shop don't know a lot about Vette water pumps, did they fit one with the correct rotation direction? Is the fan fitted the correct way. Guy had a Camaro here that kept overheating turned out the mechanic fitted the fan the wrong way round so it was pushing air towards the rad instead of drawing it away.
I have put a new temp sensor near the thermostat as I couldn't get the one in the engine out as it seems stripped but I could run it off there and just see what the diffrence is. When the first shop did the exaust they removed the smog pump and I alway wondered if maybe the water pump was running in the wrong direction but I am not sure how to check this. I have definitely thought the fan was the wrong way and I have swapped its place with no real difference.
Neither the new or old hose had the spring and I wasn't able to find one when I went looking for the replacement. I thought maybe if theis was the issue if the old hose may have failed after it was moved for the new pump as it was fine before then the new should be OK atleast for a small amount of time. I even thought maybe there was a spring I could put in myself but have not looked in to it to far.
EDIT: An infrared temp gun will take a lot of the guesswork out of diagnosing these cars. Shoot it at the upper radiator hose while the engine is running (and the lower, for that matter, to see what the temp drop is across the radiator). My temp gauge works, and is accurate (confirmed with IR gun and calibrated temp sensor), but from 160 to 200 degrees, the needle moves a tiny fraction of an inch.
Does your 81 retain the stock distributor, carb, and ECM?
Last edited by Bikespace; Dec 7, 2021 at 05:51 PM.
Neither the new or old hose had the spring and I wasn't able to find one when I went looking for the replacement. I thought maybe if theis was the issue if the old hose may have failed after it was moved for the new pump as it was fine before then the new should be OK atleast for a small amount of time. I even thought maybe there was a spring I could put in myself but have not looked in to it to far.
Try having someone rev up the engine, while you watch the lower hose and see if it is collapsing. If it does, you found the problem and will either have to find a spring for the hose, or another hose that is rigid enough to not collapse without a spring.
Check to make sure all of the foam pieces are installed between the radiator and the fan shroud so all the air is drawn thru the radiator. Also check to make sure the fan clutch is not free-wheeling when the engine is warm.
There is a urethane extension mounted behind the bumper, and a two piece rubber spoiler mounted to it. Make sure they are all in place. They help direct air thru the radiator.
Last edited by mark79,80; Dec 7, 2021 at 08:44 PM.
Try having someone rev up the engine, while you watch the lower hose and see if it is collapsing. If it does, you found the problem and will either have to find a spring for the hose, or another hose that is rigid enough to not collapse without a spring.
Check to make sure all of the foam pieces are installed between the radiator and the fan shroud so all the air is drawn thru the radiator. Also check to make sure the fan clutch is not free-wheeling when the engine is warm.
There is a urethane extension mounted behind the bumper and a two piece rubber spoiler mounted to it. Make sure they are all in place. They help direct air thru the radiator.
i agree… and posting pics is one of the greatest free consultation services to help solve the problem in the world.
I have put a new temp sensor near the thermostat as I couldn't get the one in the engine out as it seems stripped but I could run it off there and just see what the diffrence is. When the first shop did the exaust they removed the smog pump and I alway wondered if maybe the water pump was running in the wrong direction but I am not sure how to check this. I have definitely thought the fan was the wrong way and I have swapped its place with no real difference.
It would be impossible for the W.P. to run backwards by just removing accessories. You have "V" belts.
In some rare cases, a auto parts counter employee looks up SBC water-pump and accidently selects a unit for a serpentine belt system. Those pumps do run the other direction. The wrong pump, in this event, coolant would flow upwards in the radiator and out the fill neck.
Not likely your issue.
Last edited by HeadsU.P.; Dec 7, 2021 at 08:33 PM.
FWIW, the correct water pump is an ACDelco 252-585 (GM Part: 88926099). This works for 1971 to 1981 C3s with SBCs. There are fancier options, perhaps including some made in USA, but for $35-, this is the correct GM replacement. https://www.rockauto.com/en/moreinfo...t=2208&jsn=905
I bought two at RockAuto. Here's one with fresh GM Corporate Blue paint, and installed in my filthy 80 when I went to electric fans, and no accessories except for an alternator.
Do I need to get it to normal temp for this to happen?
I don't understand how a new exhaust broke a water pump or needs a new starter?
Did they have to lift the motor?
Did they use the intake to hook to when lifting?
Sounds to me like the intake at the water jackets at the head may be faulty allowing the #1 or #2 cyl to have access to the cooling system. this condition will run like you describe. OK at low rpm speeds and low loads but gets hot at higher loads.
At some point this condition warps **** and head gasket goes south.
I guess a pressure cooling system tester could expose it or testing the coolant for exhaust gasses.
Could be a head gasket or cracked head.
Sorry, I am not there or able to explain what is happening.
All I know is this condition could be what is going on.
I would like to know how a water pump gets broke for an exhaust work?
I don't understand how a new exhaust broke a water pump or needs a new starter?
Did they have to lift the motor?
Did they use the intake to hook to when lifting?
Sounds to me like the intake at the water jackets at the head may be faulty allowing the #1 or #2 cyl to have access to the cooling system. this condition will run like you describe. OK at low rpm speeds and low loads but gets hot at higher loads.
At some point this condition warps **** and head gasket goes south.
I guess a pressure cooling system tester could expose it or testing the coolant for exhaust gasses.
Could be a head gasket or cracked head.
Sorry, I am not there or able to explain what is happening.
All I know is this condition could be what is going on.
I would like to know how a water pump gets broke for an exhaust work?
What I think happened was the extractors came in closer to the block and the old starter motor was to big so they needed the smaller one. For the water pump maybe when they were removing the smog pump and doing work there, they may have removed it but I am still unsure. I still have the old one I think it looked like it may have been over tightened, and it broke around the bolt hole. I have not noticed oil in the coolant when I have flushed it or water in the oil on changes but I imagine it wouldn't take much to cause issues. I will try that test this arvo and take pics of the other things.
oil won't go in coolant. gases will. creates bubbles and hot spots, steam, that keeps coolant from flowing thru the head, then other
cylinders over heat and warp.
there are test strips that
you dip in the coolant and turn colors when gases are there.
not oil
I have tried to take all the pics I could before it got to dark
Originally Posted by Bikespace
Are you in Australia? That would explain why the shop installed "extractors" instead of "headers", and why they (possibly) sourced the wrong parts. Yeah Near Brisbane in Australia getting the right parts can be hard
I've never gotten photos to work from my phone, but it's easy on a computer. PM me if you need help, but one photo will be worth pages of speculation. Hopefully the below pics will work
Originally Posted by calwldlife
not good i am afraid.
it is going to over heat one time and take out
the head gasket.
check plugs #1 and #2 for signs of water
steaming them.
then check #4,6 #3,5
finally #7,8
I have revomed those plugs in those orders Damn forgot how hard it was to get to a few of them. it wasn't until I got to #7#8 that I had to bring the revs up that I realised I may have needed to bring the revs up higher when testing them all. But I watched and put my hand over the hole there was no steam and there was no water or coolant on my hands. I took a pic of each plug if that helps not sure what I am looking for here is #1
Originally Posted by Bikespace
FWIW, the correct water pump is an ACDelco 252-585 (GM Part: 88926099). This works for 1971 to 1981 C3s with SBCs. There are fancier options, perhaps including some made in USA, but for $35-, this is the correct GM replacement. https://www.rockauto.com/en/moreinfo...t=2208&jsn=905
I bought two at RockAuto. Here's one with fresh GM Corporate Blue paint, and installed in my filthy 80 when I went to electric fans, and no accessories except for an alternator.
Please post a photo!
Here is my water pump. The broken shield happened after it started over heating it broke a engine mount and the fan went through the shroud
Originally Posted by Fly skids up!
On a cross flow radiator a easy way to see if you have flow remove the radiator cap and see if the coolant level drops when you rev up the engine.
I didn't bring it fully up to temp but there was a small drop of coolant I have a small vid of this if it helps
Originally Posted by mark79,80
Try having someone rev up the engine, while you watch the lower hose and see if it is collapsing. If it does, you found the problem and will either have to find a spring for the hose, or another hose that is rigid enough to not collapse without a spring. I got the misses to rev the engine and I couldn't feel any movement.
Check to make sure all of the foam pieces are installed between the radiator and the fan shroud so all the air is drawn thru the radiator. Also check to make sure the fan clutch is not free-wheeling when the engine is warm. There is foam between radiator and condensor there is a gap between the shroud and radiator maybe more than the foam.
There is a urethane extension mounted behind the bumper, and a two piece rubber spoiler mounted to it. Make sure they are all in place. They help direct air thru the radiator
Here is what is behind the font bumper I don't think the spoiler extention or the defelctor is there I dread trying to get them in Australia but it might be the answer??
The water pump looks correct. It is the correct "depth", right up against the timing cover, so I don't think that is the problem. The fan blades are pitched correctly of course.
You are missing not just the rubber "lip" on the lower extension, but the extension itself. I think that's called the "Center Valence Panel", or perhaps "Lower Bumper Extension". The rubber parts are the "Front Lower Spoiler Air Dam Extensions". Links below, with a photo of what it looks like in my 80 (mine was replaced by a PO, and says Ecklers on it somewhere, so shearing them off appears to be a common problem).
81 Overheating issue
