Hissing noise, and IC tubes

keithw

Registered User
OK, I am trying to diagnose a difference set of problems. The car dies at idel, but not every stop light. When we turn off the engine, I hear a hiss that decreases to silence after the engine is OFF. I think the IC tube was removed to change the water pump for some reason. I want to go make sure they are sealed. It sure sounds like it is coming from the upper tube near the intake on drivers side. What tool do you use to loosen this type of spanner flange up with ? Thanks.
 
First check all you connections with propane, starter fluid, etc to check for vacuum leaks. That will help find the problem instead of just removing parts needlessly.

The "hissing" is common when you turn the car off. Next time you do that, watch the boost guage. It will stop hissing when it gets back to the "0". The supercharger is continually producing boost, because it is belt driven. The system will have pressure in it when you turn off the car. The hissing is just that pressure escaping back out and equalizing the system pressure to the normal outside pressure.
 
Yes, however, the supercharger is still spinning compressing air...The bypass valve enables the supercharger to continue that even though it is not required by the engine. Thus the supercharger, and IC system up to the bypass valve have "boost" in them even in vacuum. The bypass valve is open though to prevent cavitation. The hissing is that pressure being released.

Point is that the hissing is normal. If you hear a whistling at idle, that is a sure indication of a vacuum leak. Not all vacuum leaks will be audible though. That is why I suggest you check all connections with the propane or the such before you arbitrarily start replacing sealed joints if you don't need to.
 
007_SuperCoupe said:
Yes, however, the supercharger is still spinning compressing air...The bypass valve enables the supercharger to continue that even though it is not required by the engine. Thus the supercharger, and IC system up to the bypass valve have "boost" in them even in vacuum. The bypass valve is open though to prevent cavitation. The hissing is that pressure being released.

Point is that the hissing is normal. If you hear a whistling at idle, that is a sure indication of a vacuum leak. Not all vacuum leaks will be audible though. That is why I suggest you check all connections with the propane or the such before you arbitrarily start replacing sealed joints if you don't need to.

That's not correct. Unless the pressure is above atmospheric then there isn't any "boost" the system is under vacuum at idle. When you turn the car off air is forcing itself past the throttle body and into the IC tubes and related components due to the pressure differential, this is the hiss you hear. When you shut the car off the blower stops moving same as everything else in the system.

The air is circulating and is lower in pressure when the engine is running under vacuum. The bypass is not there to prevent cavitation that is the crosstalk tube's job, and is only needed because of the small TB and MAF that is on the car stock. The bypasses job is to reduce the load on the SC when it is not needed. Cavitation at idle isn't going to hurt the SC it's when the system is under load that the problems occur. When the system is under vacuum the pressure is equalized and no cavitation occurs.

Jeff
 
OK, Not to turn this post into a Super Charger post, but with our Blown Hemi stuff...
With a Keith Black blown 610 inch Hemi making 2000 HP, we still draw vacuum at idle. The blower even at idle still does not move enough air to produce a surplus of intake charge, thefore, there is a vacuum. When the blower/engine speed up, it then draws more air than the natual aspiration process, and bingo, forced induction, aka boost.

Now, onto my post, The hiss, I finally located it. Working alone is tough. I sprayed the tubes and joints with ether, and nothing. I drove it a little bit, It got rough at stop lights, but did not die. I pulled back into the shop. I heard the hiss at idle. I sprayed the same place with ether. Varoom. It just needed to heat up and move around a little bit. A very positive signal of rpm rise.

I took a wide, dull chisel( I made it for spanner rings on another project) that I ground flat on the end and hammered the spanner on the upper IC tube. It moved with somewhat ease. I took the IC tube off and cleaned the heck out of everything. I dont want to take a chance. If it has been leaking, It has crap in the flange. And it did. I used some HIGH TEMP Copper and let it set up.
The Ford Dealership said to just use the o2 safe copper on them. And I did. I also cleaned out the already clean IAC very carefully. I am going to let this stuff setup before running it. Thanks. Cross your fingers
 
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Aha, just like I said in your other post! (Sorry, just a slight pat on my own back) That copper RTV is fine, I used it myself. Don't rev it too high for the 1st 24 hours or so. I think it needs time to set up before you put it under boost.
 
Keith,

There is a special wrench that is used on the SC top nut. You can find them on the board or usually on Ebay. Using a chisel can crack it. The nut is pretty thin and easl cracked. Vacuum leaks on a car with a MAF sensor will cause the problem you described.

Jeff
 
No more hiss, no more stalling. The car runs about 3/4 the way to hot on the guage. The fan is running, I checked the coolant. It is full. It can jump to hot, and if I back off and cruise, it cools down, but not to the center. I am chasing problems left and right....
 
If I remember correctly from your other thread, you just changed the water pump, correct? I was having similar sounding problems recently, & I changed both temp sensors, the one that feeds the gauge, & the one that feeds the computer to control the fan. I also changed the t-stat. Didn't seem to help. Anyway, I still had the problems & eventually it stopped. My thinking is I might've had air in the system, & it just worked itself out after a few days. There's an air release "valve" on top of the engine. You could try opening that.
 
Now that I am not so sleepy. My girlfriends step dad changed the pump. She drove it for 6 months no problems other than dead engine at stop lights. Not overheating. She parks it in the shop for 1 year, with occasional startups to keep the oil and all circulating. Now, we are moving 10 hours from here and am trying to get the car worthy(if it has to, otherwise the Dodge will tow the Ford,what is new). So, basically the car ran fine other than stalling occasionally. Since I fixed the stalling, I mean when you goose it and build 3 psi for 400 yards, it jumps to 7/8 hot, Not in the read, still a couple of needles off the red. Drive it easy, it goes back down, but still not in between the C and H . When I first dove into this project a week ago, It ran for a long time, idled, drove it in the long 1 mile drive to burn off the surface rust and all on the rotors.

It ran good and cold then, why hot now? The check engine light stays off for the most part with an occasional flash. Now, when this thing was getting on up there temp wise, I jumped out, the fan was off. This fan should run way sooner than it does. By the time the fan comes on, it is almost too late. The Antifreeze level is perfect and very clean.
 
It sounds like you have air in the system still. Check your rad cap. The Sc is probably the hardest car I have ever had to purge air in. The upper Rad hose is the highest point in the system, that's why there is a stem with a bolt in it that runs from the thermostat housing. When you fill the system you need to remove it and fill the rad until coolant comes out of the stem then plug it. Make sure to use a back up wrench on the bottom of the stalk or you might twist and break it.

After it's hot shut the car off and see if coolant purges into the overflow tank.
I had the same problem when I first got my SC and it drove me crazy for weeks.

Jeff
 
I just went through this a few weeks ago. I'd make sure the temp gauge is getting the right temp sent to it. There are 2 coolant temp sensors on the top of the engine. I forget which is which. One is right by the t-stat housing, & the other is by the fuel lines by the oil filler cap. One is for the gauge, & the other is goes to the computer to control the fan. I'd probably change them both. I just did that on mine. One cost about $17, & the other was about $5. If your gauge isn't reading right, the car might not actually be getting hot at all. If it is hot, then the other sensor (actually called the ECT sensor) might not be turning the fan on.
Here's a helpful link about T-Bird cooling systems:
http://www.mn12performance.com/mn12-techinfo/cooling/cooling_system.htm

Mike
 
I agree with Jeff here, too. I changed the sensors & my gauge still seemed to hunt around some. It kept draining the reservoir for a couple of days before it stopped. I thought then that I still had some air in the system.
 
Thanks yall, I'll try to purge it again tomorrow. What baffles me is that 90 degree day we let it idle and drive it in the drive for an hour, and it was dead center on the guage
 
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