96powerstroke

Hi Folks,
I just picked up what looks to be a pretty darn original '70 cutlass supreme in great shape. The motor may have had work done but I can't tell. It's got 70,000 miles on the clock so I'd like to think it's all original. A previous owner did install a HEI distributor and paint the engine block - which makes me believe the motor may have been pulled. The paint looks like parts store gold but it looks to be done well (as in they removed brackets. etc...).

Long story short here.... when the engine is cold I get a strange air-horn like noise at a particular RPM. I don't have a tach and haven't put one on the car yet but I'd say it happens around 1500 to 2000 and goes away.

My first thought was belt but it's not a belt squeal. It sounds more like it could be a bad bushing... I don't see any water leaks but could be anything on the accessory .

The noise is best described as a quiet air horn. It doesn't come on full blast but quickly increases in volume the way an air horn would (as opposed to an electric horn) .

Belts look good and I've looked but the noise seems to scatter around so pin-pointing it is difficult. Just thought I'd see if anyone has experienced anything similar in their travels.

Thanks,

oldcutlass

You could remove the belts then run it briefly and see if its in the accessories? Could it be a the cooling fan with a tight fan clutch?

gs72

This will sound weird but some early to mid 90s Fords had a similar noise coming from the heater core. The fix was a orfice fitting we would splice into one of the heater hoses. Just pinch off one of the heater hoses to eliminate this as a possibility. The problem was in the heater core but the cheaper fix for the factory was the orfice. Just throwing it out there.

96powerstroke

Good call. sometimes I miss the obvious. DOH! No accessories would at least rule out the water pump (or rule it the water pump).

Thanks...as a mid 90's ford owner. Mine doesn't make such a noise but it's also a diesel and you can't even hear yourself think while it idles. Something else to keep in mind.

Fun71

I think this is a definitely a possibility. The factory used a restriction in the inlet heater hose to reduce pressure/flow through the heater core. AC cars have a vacuum controlled valve and non-AC cars have a hose nipple, and both styles have a small hole (1/4" maybe) in the threaded base portion as a restriction. If you don't have that restriction the heater core can moan as the water flows through it.

96powerstroke

Unfortunately I did a little more diagnosing. The noise seems to be directly related to engine speed (when cold) which almost certainly points to one of the belt drive accessories. However that being said, water flow is also directly related to engine RPM... The noise does appear to come from the front of the motor but I also realized I don't have any heat. I think the coolant control valve (the one atop the motor that uses vacuum from the control head to open/close) may not be working...or if it is and my heater core is plugged up this could also be culprit.

I'll dig a little more when I have a moment to. Although it's not getting put away for the winter just yet I would like heat and for that noise to be diagnosed.

Thanks for the input!!!

jpc647

If you have anyone that can help you, most part stores sell cheap stethoscopes, that are instrumental in pinpointing things like this.

Even a medical store. "Disposable" stethoscopes run about $10.

Greg Rogers

Piece of vacuum hose is the cheapest stethoscopes available.... put one end in your ear and listen around... it works !!