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How Do You Fix A Freeway Speed Rattling Hood On A C10 Or K5 Blazer Or GMC Jimmy

B

Bohemian

Guest
maybe my google fu is off today, but I can find plenty of stuff on hood adjustment but not how to stop the hood from rattling at highway speeds. It seems like a common problem on the 81-91 K5 & the 1981-87 C10 and the only thing I've seen folks do personally to stop it is aftermarket hood pins. Which I'd rather not do to a perfectly good stock hood.

So my K5 is a 1982 so it came with the redesigned hood that fixed the hood buckle in front of the hood hinges issue on the earlier models.

My hood as near as I can tell is the original, I put a new GM NOS Hood Latch, release cable, and hood bumpers, stops. I do not see any hood separation and the hood hinges appear to be ok and it closes good and solid.

What I observe is mostly at freeway speeds, the front of the hood is rattling or flopping or lifting up and down.
Looks like hood pins would be a cure; but I know at least the 1981-1987 C10 & 1981-1991 K5 Blazers did not do this from the factory. I bought a brand new 1982 C10 back in the day, had it about 5 years before I sold it and that hood never did this.

So I'm thinking there's something I'm missing tip or trick wise to eliminate the need for hood pins.

thanks in advance.
 
Is the movement at the front or rear? If the front, are you sure the latch is adjusted to the correct height? Seems like the only way the front would be moving is if the hood is not completely latched and only in the safety catch (like after you've pulled the release cable).
 
nvrenuf said:
Is the movement at the front or rear? If the front, are you sure the latch is adjusted to the correct height? Seems like the only way the front would be moving is if the hood is not completely latched and only in the safety catch (like after you've pulled the release cable).
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I don't see the back moving, it's lifting in the front, at highway speeds, I can see it going up and down next to the drivers side front fender, from a driving perspective. The hood latch is new NOS GM and that big old heavy hood does not appear to move very easily after the very solid, pleasing hood closure. In fact I have to give the hood the fonz hammer fist hood bump over the top of the hood latch to get the hood to fully pop up after the cable has been pulled, it does not pop quite enough because the latch closes so tight. Perplexing to me why that hood moves at all at any speed, I don't see it moving at 45mph which is about as fast as I can legally go around town in most places; but jump on the freeway and about 60mph plus I see it rattling or lifting up and down by drivers side front fender is about as good as I can describe it.
 
@Fastereddie an I were just discussing this. My 91 does this to the point I’ve pulled over to check it. Everything is good on my truck, so I’m in to see if there’s a solution besides hood pins also.
 
The fact you have to fist bump the hood to open it indicates some adjustment needs to be made somewhere.
 
How are the core support bushings ?...if they are rotted or loose the nose can jump around and make the hood flutter..also the two bolts behind the front tires that hold the inner fenders to the firewall often have the inner fender rot around the bolts and are no longer securing the nose well--I see many trucks that had them patched over with no bolts put back in..
 
diesel4me said:
How are the core support bushings ?...if they are rotted or loose the nose can jump around and make the hood flutter..also the two bolts behind the front tires that hold the inner fenders to the firewall often have the inner fender rot around the bolts and are no longer securing the nose well--I see many trucks that had them patched over with no bolts put back in..
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Ding! Ding! Ding!
Forgot about the core support. Good call. :waytogo:
 
Bohemian said:
I don't see the back moving, it's lifting in the front, at highway speeds, I can see it going up and down next to the drivers side front fender, from a driving perspective. The hood latch is new NOS GM and that big old heavy hood does not appear to move very easily after the very solid, pleasing hood closure. In fact I have to give the hood the fonz hammer fist hood bump over the top of the hood latch to get the hood to fully pop up after the cable has been pulled, it does not pop quite enough because the latch closes so tight. Perplexing to me why that hood moves at all at any speed, I don't see it moving at 45mph which is about as fast as I can legally go around town in most places; but jump on the freeway and about 60mph plus I see it rattling or lifting up and down by drivers side front fender is about as good as I can describe it.
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I have the same problem with the movement and the hood needing the fonz bump to open.
I have adjusted the bump stops so high and I still see movement and it still doesn't pop when I pull the cable to open.
 
Do you have the little rubber bumpers on the fenders? There should be 2 on each side.
 
There should be some rubber bumpers on the top inner edges of the fenders also if I remember correctly,around the halfway point..

Any out of round or imbalanced front tires might cause the hood to shake also..
 
diesel4me said:
There should be some rubber bumpers on the top inner edges of the fenders also if I remember correctly,around the halfway point..

Any out of round or imbalanced front tires might cause the hood to shake also..
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I have the rubber stops and it's the wind not the suspension that makes the corners lift and as far as I know it's original hood
 
Maybe the hood is solid but the fenders are sinking?

Perhaps the hood just doesn't fit quite right and it needs to be carefully bent down at the outer corners. You should have a basically straight gap between the bottom of the hood and the core support.
 
My hood sits good, and at less than about 45mph it doesn't budge, but get on freeway and the front corner of hood is raising above the fender line that it's normally level with.

I have 4 rubber bumpers total 2 on each side of hood and the 2 adjustable ones in front and the hood to cowl seal in back.

Everything is new as far as that stuff goes and the hood latch is nos gm.

I just noticed on lmctruck that it shows 6 rubber bumpers 3 on each side so I ordered a new set and I will see if that does anything.
 
Bohemian said:
My hood sits good, and at less than about 45mph it doesn't budge, but get on freeway and the front corner of hood is raising above the fender line that it's normally level with.

I have 4 rubber bumpers total 2 on each side of hood and the 2 adjustable ones in front and the hood to cowl seal in back.

Everything is new as far as that stuff goes and the hood latch is nos gm.

I just noticed on lmctruck that it shows 6 rubber bumpers 3 on each side so I ordered a new set and I will see if that does anything.
Click to expand...
I know exactly what your talking about. My blazer does the same thing. Hell, when you pass an on-coming semi, the hood looks like it’s going to fly off. Haha! I also have all the rubbers and latch adjusted great. I am starting to think the sheet metal in the hood is just fatigued from 20 plus years of flexing. I hate to say it but I’ll probably end up using hood pins to hold down the corners. :doah:
 
I just bought my 'new to me' 88 K5 and stopped on the way home to see if I had closed the hood correctly! Not sure if this will work, but here is a copy of that page with part numbers. 30-1822 Hood Bumper Side (6) 76-91 $1.95; 30-1824 for 76-81 front and 30-1826 for 82-91 front (2) hood bumper front.

Hood Bumper side and front page 39.JPG
 
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