Overheating

[Anthony]

Dear club members. Have a C4 corvette in my shop with a coolant overheat issue. The water pump is noisy and whines loud. I put my hand on it and it feels like the pump. Could it also be the internal drive. I have a new pump Cardone but am reluctant to replace it if there has been issues on this forum. Your help would be appreciated.
Thank you
Anthony

 

[XFIRE82]

You need to tell us what year of c4, as 93-96 is totaly different than the earlier ones. As with any pump replacement, new rad hoses and heater hoses are good to replace also so you don't have to do this all again . Should be someone on here that can guide you as I haven't wrenched one of these yet.

 

[Anthony]

Thought I mentioned that, it is a 1994 corvette 5.7 litre convertible. The lady said last week when it was hot here in peachland she got home and she could hear the water gurgle in the engine. She also lost a bit of water. This is what I did. Pressure tested coolant tank cap and it failed. Vented at well below 16 psi. Figure was 10 psi hence it ran the overflow into the plastic bottle, at least that’s what I think, because no water in plastic tank. Do I replaced thermostat and cap. When I started the engine the pump whines very loud. Almost like performance straight cut timing gears. I have a pump but as I mentioned in my post don’t want to install it till I hear from you good people out there. I have worked in this trade 46 years and not shy to say I am still learning. Thanks
Anthony

 

[XFIRE82]

So this is a LT1 5.7, same thing I just recently bought and lucky for me the pump and optispark were just changed. From what I know, the pump is driven by a shaft from the front of the block. It is important to change the oil seal on that shaft also when the pump is off. Apparantly when the pump leaks, it drips on the optispark and it can screw it up also. GM did a poor design there. I've read where guys tap a drain hose onto the pump vent hole at bottom and if the pump should ever leak then it won't drip on the costly optispark. Check the hoses but always good to put them new also as it is not as easy job . Guys say you might need to go to a chiropracter after this job of changing the pump. ????? a/c compressor will have to get moved off but think you don't have to drain the freon but the brackets are not easy to get at . Good idea throw a new thermostat in while coolant is drained. Best maybe look on You Tube and there I'm sure are video's of guys doing the pump change. Or someone here can chime in and give better advice . Just wondering if the whine you hear is not the electric fan motor on the rad ?

 

[Anthony]

Thank you so much for the advice XFIRE 82 for the generous information. I know for sure the noise is directly on the water pump but not sure if it is the unit or the drive from the engine. Coolant fans were off at the time. I don’t do a lot of corvettes due to the very low clearance under belly and I cannot get the arms of my two post lift to swing under unless I go and jack each corner at a time. A pain for me, besides when I worked at the dealer I was told always release the top from the windshield as it could pull the shield and crack the glass. So for years now I undo the latch before raising the vehicle.
Thanks again for the good advice
Tony

 

[XFIRE82]

No problem Tony , I'm old school as most guys on here know , so this new stuff is not exactly my bag . But make sure you change that oil seal as apparantly they do eventually leak and while it is apart then this is the time to get at it with the pump off. My hoist is antique like me , single pole with the rails , air over hydraulic, I can spin the car around 360 if I want , works great for what I do. But like you say these cars are low so I just put some short 2 x 6's in front of the tires and drive on them , thus I got more clearance to put the blocks under it to raise it up safely , maybe driving on the planks would help you not having to jack it up prior ?

 

[Anthony]

Thank you for the pictures. Your shop look very good. Very much like the British shops when I lived in London. I will send you some pictures too in a few days. Thanks a bunch

 

[12cents]

Changing the water pump is back-breaking work. I did one on my old 1995 Z28. GM did a poor design with the opti-spark below the water pump but mine was still original when I sold it. Your 1994 has a vent in the opti-spark which alleviates most of the internal corrosion issues. the first year of the opti-spark (1993) did not have this vent and suffered horribly for it. Before changing the pump, I would go ahead and replace the radiator cap, top up the coolant and see if that was the problem. If it is the pump, you have my sympathy. Your back is going to be sore and your arms tired from reaching (mine were when I finished). These pumps are year specific. During the lifetime of this LT1 engine there were three different versions. And of course each had a slightly different way of driving the water pump among other variations. The pump is driven off the cam shaft with a pin. The pins are different for each of the three versions of the LT1. From what I remember of my old Z28, there was no oil seal to mess with. My biggest pain was cleaning the old gasket off the mating surfaces on the engine. Hope some this blather helps guide you. Looking forward to some pictures as you do this repair.

 

[Anthony]

Thank you for the insight. Fortunately at 68 years of age I am pretty flexible, but you are very correct about back being sore. I will get detailed pictures and a sound bite of the noise if I can produce it without other interference. I cannot for some reason get an AC Delco water pump don’t know why from our local store in BC Lordco. I have a cardone one and hope I don’t have a problem with warranty.
I will do my best this week to remove and record my work job.
Thank you again very much
Anthony

 

[Anthony]

This is a specific post to my original query to the overheating 95 corvette with the water pump whinning issue.
In the end I decided to best remove the water pump for inspection after doing a pressure test with no leaks found. On removing the unit, it was found that the impeller splined drive could be felt to bind when turning with fingers. I had a new pump with me, so installed it and Presto!!!! No noise. Ran good fan kicked in on road test no problem. Checked everything else also installed new thermostat again, just in case.
Thanks to many of you fellow members that sent me very informed replies. Vehicle ran very quiet (usual corvette sound) and more stable engine speed.
Thanks again to All.
Tony

 

[12cents]

That is awesome news to hear.

 

[XFIRE82]

good job , glad to hear you got the problem solved. and the Vette is back on the road.

 

[Anthony]

Yes the vette was back, so did not hear from the lady again. Also I did not post this, but both the tensioner and idle pulley were so badly deformed. I have not seen this anytime in my 46 years in the trade, have any of you? I will attach a picture.
The other thing I would like to know is , how do you guys jack up the car,? I can’t even get my two post hoist pads to slide under the jacking points. I have always ( with a convertible ) released the top fully from the windshield before hoisting in the air. I was told this a long long time ago when I first came to Canada, due to the body flexing, that can pull the windshield and crack the glass.
Advice from you experts would be great. Thanks
Tony

 

[XFIRE82]

Hmmmm, my uneducated guess would be : first is that a plastic pulley ? some point in time that belt may of been stretched to as where the tensioner was at its limit and the belt was slipping. Or the bearing had siezed in the pulley and the belt wore the spots ? then some mechanic didn't have a new pulley so he just replaced the bearing ?
I drive the car on some 2x6's (planks ) which raises the car enough to stick anything under there to access the lift points.

 

[Darrellg1]

Hmmmm, my uneducated guess would be : first is that a plastic pulley ? some point in time that belt may of been stretched to as where the tensioner was at its limit and the belt was slipping. Or the bearing had siezed in the pulley and the belt wore the spots ? then some mechanic didn't have a new pulley so he just replaced the bearing ?
I drive the car on some 2x6's (planks ) which raises the car enough to stick anything under there to access the lift points.

Yep, I do the same Tony, I use 2x6's and rhino ramps behind that if I need the ramp set up, or as X-Fire say, to raise the car the few crucial inches to get a low profile jack under it. Lordco sells a fairly decent "NASCAR" Low profile jack we used in the tow truck shop alot. They have a quick raise ram on them, so a few pushes on the handle gets it raised pretty fast.
That pulley loks a bit flat spotted, possibly from a tight serp belt, or the idle pulley bearing sticking. Was there a grinding or bind feel to it? Something else in the belt train may have caused it too, possibly even the pump impeller issue causing it perhaps?

 

[Anthony]

Yes you may be right about a binding pump come to think of it. There was another Corvette I did about 3 years ago newer to this one 2001 that had a overheating issue and I had put a new pump into that one but the customer who knows a lot about cars a custom car graphics girl, said it overheats, I checked it after the repair and found that the fan cut in at around 225F. Do I did ring at that time a man in Calgary corvette club and he said corvettes ran up to around 240 F due to the slopes radiator and not enough Ram Air effect.
True or untrue I cannot confirm. I driven a few but only on road test.
Thank you

 

[Darrellg1]

Yes you may be right about a binding pump come to think of it. There was another Corvette I did about 3 years ago newer to this one 2001 that had a overheating issue and I had put a new pump into that one but the customer who knows a lot about cars a custom car graphics girl, said it overheats, I checked it after the repair and found that the fan cut in at around 225F. Do I did ring at that time a man in Calgary corvette club and he said corvettes ran up to around 240 F due to the slopes radiator and not enough Ram Air effect.
True or untrue I cannot confirm. I driven a few but only on road test.
Thank you

I can relay my personal experience with the coolant system in these cars.

I JUST last weekend replaced the radiator in mine. I took it to Princeton, on the Hope Princeton highway with an OEM Thermostat which is a 195 f and it ran 93-95 degrees Celsius or just north of 200 F all the way. So yes they run that warm, I HAVE noticed tho the radiant heat isnt as bad after parking the car in the garage after work since the rad change. Due to the better heat exchange, one would assume.

 

[Anthony]

Thanks for that good to know

 

[XFIRE82]

a binding water pump would not cause the idler to wear , that pump is shaft driven and it will turn or snap / strip something, or if the pump seized I'm sure the engine will stop. I've seen a few alternator sieze and the motor stops can't turn it over , the serpentine belt has such a grip.. The idler pulley will only jam if the bearing fails then the belt will start to slide on it instead of rolling along. I'm sure a lower temp cut in switch could be installed to get the fan turning sooner. When I built my 49 I put in a 180 cut in switch and it works fine.

 

[Anthony]

Thank you, I was not thinking.? I am a drivability tech. Do much say less I have to say for me. My thinking was if the water pump (one cause of many) partly jerked by binding the pulley had motion then suddenly stopped at the exact time the pump bound. Does not matter now. I fix with most good intentions for no COME BACKS!!!
Thanks for your time with my post.
Best regards
Tony