Hi guys..........I really need some help on this one. I purchased my 77 vette back in January this year and shortly after getting it, I have been hearing a noise that sounds like it is coming from an area in front of the passenger side of the car. The best way I can describe the noise is that it sounds like a "churning" noise (like the sound of fluid being forced through something), or like bearing getting ready to go out. I originally thought it might be coming from the heater core in the passenger side dash, but this past weekend I bypassed the heater core by routing a hose from the water pump directly to the top of the intake. I drove the car and still heard the noise. I don't hear the noise until the engine is at operating temperature. The engine runs well and the transmission shifts perfectly. When I take off from a stop, and just ease onto the throttle taking off slowly, that is when I hear the noise. I can even make the car replecate the noise when I am sitting still with thet car in park by just easing down on the throttle while idling. I just can't determine what the problem is on this thing. When the car is sitting and idling, I can't hear it from inside or outside the car. It only makes the noise when I am giving it some throttle. The noise sounds pretty serious. Any ideas on what it could be? I am thinking that the next thing to check might be the water pump, although it is not leaking? Any help would be greatly appreciated.

thanks

 

Check the lower radiator hose, as it might be collapsing and you're hearing water squeeze past it. Also, it might be the T-stat not opening fully.

Try to have someone else operate the throttle, or you do it from the engine side, and see if you can tell exactly where it's coming from with you right on top of the engine.

 

Thanks, I'll check that out. Never thought about those two things. I'll let you know what I find. Thanks again.

 

Well, I am still trying to determine the cuase of the noise I am hearing. I did find that my right exhaust manifold was warped due to one of the manifold bolts not being tight, however this was not the cause of the noise I am hearing.

Here is a recap of things that I have done thus far to the car to try to determine the cause of the issue:

#1) By passed the heater core and water valve to rule out possible noise of coolant flowing through a partially blocked heater core.

#2) I have checked to make sure the radiator hoses were not collapsing.

#3) Ruled out the manifold exhaust leak is not the issue causing the noise.

#4) I have listened to all the major components with a mechanics stethoscope i.e., water pump, power steering pump, ac compressor and alternator and have ruled out that they are not causing the noise.

#5) Confirmed that the coolant thermostat is working properly.

#6) Confirmed that the fan clutch is working properly.

Facts about the noise are:

#1) It only does it when the engine is hot at operating temperature
#2) It makes the noise when the car is in gear when easing on the throttle.
#3) The noise is directly linked with the engine RPM's and not the drive train i.e., drive shaft etc.
#4 The noise seems to be coming from the right side of the car toward the rear of the engine.


The noise still seems to be coming from the right hand side of the engine, and from inside the car it sounds like it is near the firewall. When sitting and idling, you can just barely detect the noise. But when I put it in gear and start to ease to a start, the noise magnifys in intensity. I had my son stand outside the car and he said he could really hear it loudly from the outside too when I start to take off. This noise only occurs once the car engine is heated up at running temperature. The noise definitely is linked to the RPM's of the engine and not the drive train because the noise that intensifies as I am giving the car throttle goes along with the engine rev and not the turning of the wheels, driveshaft etc. I am pretty much stumped at this point and don't know what to try next.

Could it possibly be something in the transmission, i.e., torque converter etc? The transmission seems to be shifting fine.

I really hate the thought of taking it to a garage as I am afraid they won't be able to determine the cause easily either, and will end up scratching the paint etc. I have had so many bad experiences with garages that I just shutter at the thought of leaving my Vette with a GM garage. And it has been my experience that problems like this lead to about 14 trips to the garage and no success of them finding it.

Getting pretty desperate at this point. Any suggestions, tips or advice would be greatly appreciated.

thanks

 

double check your header n gaskets ?
check for bad valve?

 

You're getting good technical advice here. If you need to go to a garage check with other Vette owners to see where they go. Sometimes the mechanic down a gravel road with two bays is your best bet - always get a written estimate.

 

Hi V77Vette,

I don't have headers on the car, just the original manifolds. I just had the one machined on the right side of the engine and installed it this past weekend and added a gasket.

The noise I am hearing sounds more like a bearing going out, sort of like a churning/grinding kind of noise.

thanks

 

[I am assuming that you have an automatic transmission.] When you shift into 'drive', the tranny activates two internal clutches; it also changes the pressure schedule of the tranny. Since the sound you hear is linked to engine RPM...and not driveshaft speed...I would surmise that your problem has something to do with the charging pump in the transmission. Apparently, the added load called for when you shift into drive is causing the charging pump to change its behaviour such that it makes a different sound. It is possible that your tranny fluid is a bit low and when you activate the internal clutches (filling them with more fluid) the oil level is below what the tranny would like and you are hearing some flow cavitation noise from the pump sucking air. Check your tranny oil level when warm, idling, and on level ground. It should be up in the "hot" range. If not, you are running low. If the oil level appears to be OK, your charging pump is just showing signs of long-term wear. Until you have operational problems with the tranny...or the noise you are hearing changes significantly..., I wouldn't take any repair action at this time. When it starts annoying you further, take it to a good tranny repair shop.

 

You are correct 7T1Vette, I do have a automatic transmission. I only hear the noise when the car is at operating condition and is hot. When I first start it up and take off, I don't hear the noise. Is that still indicative of the possible cause you describe above? It is pretty much at the stage where I can't stand it. The car is immaculate inside and out, with perfect paint and fully restored interior. I can't stand for it to look as good as it does but sound this bad. The noise is very apparent even from the outside of the car. If this is the problem, will it take a tranny rebuild to fix it? Thanks for your help.

 

Could it be something as simple as a heat shield ????
Todd

 

this may seem off base but because you said the car does it when warm check to see if the catalytic converter is not leaking when engine is warmed up

 

Does the tranny have a shift kit installed? I built my TH400 to the B&M st/strip spec's and I have a clunk sound at low speed like off idle. The mod to the pump pressures is the result of the noise and only when I'm at low rpm otherwise it shifts fine and hard if nailed.
Maybe not your problem, just throwing it out there.

 

Only one way to know if the tranny oil is low.....check it!

 

you got air conditioner?
may be it has bad bearing

 

No tranny kit installed. All is original. thanks

 

Hi 7T1Vette,

No, it's not the transmision fluid level. Early on in the beginning of trying to determine the cause of the problem, I checked all the easy things first, including checking all the fluids etc. Just my luck though, it is never anything easy. ha ha ha thanks for your help.

 

I do have an air conditioner, but I have used a mechanics stethoscope and did not hear the noise coming from the compressor. I may try removing the belt from the compressor and running the car down the road to see if I still hear the noise.

 

Then, I'd say it's a problem with the transmission charging pump. That's not something that you would get repaired without a complete rebuild. Wait until it gives you some operational problems before you put $$$ into a tranny rebuild.

 

don't know much about cars but I'm just going to throw this one out there, it happens when the engine is warm and sounds like it is coming from the passenger side just in front of the firewall, that is exactly where the coolant overflow is.

 

Could it be the Heat Riser sticking or getting stuck restricting exhaust flow...as you stated it is stock..maybe as it gets hot making exhaust sound like fluid transfer? Just throwing it out there.