1994 GMC Sierra K1500 5.7l ticking

[Gartole]

Hello,
I am just trying to gain some knowledge about my truck. So my vehicle has recently started ticking. Not like it has any performance issues, when I have foot not on gas or it is maintaining lower speeds, I hear nothing. Once it is under load, it begins to tick. At first I thought it was like valvetrain chatter. 30 year old engine, no rebuild. Bound to have some, right? But in the colder weather we’ve been having it has become increasingly louder. Which made me think it may be a broken exhaust manifold bolt. To my knowledge the truck has been maintained religiously. I change oil no more than 2500 miles and let it warm up. It does not burn any oil. I am 20 years old but I treat it with respect as it’s my only vehicle to get to college so it’s not like I’ve got the funds to run it into the ground. I drive it at least 60 miles a day back and forth to school. I am somewhat mechanically inclined so I’d like to take care of it myself if possible. If you have any ideas as to how I could do some process of elimination and determine what the issue is and if I can fix it myself (realistically). That would be greatly appreciated.

 

[Erin]

Hello,
I am just trying to gain some knowledge about my truck. So my vehicle has recently started ticking. Not like it has any performance issues, when I have foot not on gas or it is maintaining lower speeds, I hear nothing. Once it is under load, it begins to tick. At first I thought it was like valvetrain chatter. 30 year old engine, no rebuild. Bound to have some, right? But in the colder weather we’ve been having it has become increasingly louder. Which made me think it may be a broken exhaust manifold bolt. To my knowledge the truck has been maintained religiously. I change oil no more than 2500 miles and let it warm up. It does not burn any oil. I am 20 years old but I treat it with respect as it’s my only vehicle to get to college so it’s not like I’ve got the funds to run it into the ground. I drive it at least 60 miles a day back and forth to school. I am somewhat mechanically inclined so I’d like to take care of it myself if possible. If you have any ideas as to how I could do some process of elimination and determine what the issue is and if I can fix it myself (realistically). That would be greatly appreciated.

I had a similar issue & it was a lifter tick.

 

[texas tough]

I would try a bottle of marvel mystery oil. been using if for many years. it can free up alot of sticky components, no risk . I add it to my gas too.

just turned 200,000 on my 94 k1500 and it runs great.. I use Valvoline oil and wix oil filters. I put the best parts I can get on it when something needs replaced.

 

[Schurkey]

when I have foot not on gas or it is maintaining lower speeds, I hear nothing. Once it is under load, it begins to tick.

Lifters don't know when the throttle is being pushed. They don't tick louder when the engine is making more power.

Ticking that varies with throttle position is more-likely an exhaust leak--headers are infamous for "blowing out the gasket" which can tick like crazy. Iron exhaust manifolds generally don't use gaskets--so broken bolts, failing donuts, warped flanges, and cracks are the more-likely possibilities. The manifolds often crack under the heat-shield where you can't see it easily.

The first two things I'd look for:
1. Count all the bolt heads on both exhaust manifolds. My '97 7.4L is missing a couple on each side. No bolt head = no clamping force = very likely an exhaust leak plus likely warped. You'll have to remove the manifold(s), remove the broken bolts and assure that all the bolt holes still have usable threads. Then plane the manifold to get it flat and smooth again. Reattach with new hardware. I would use anti-seize on the threads; but then I anti-seize, lube, or threadlock just about everything.

2. Check the donuts where the exhaust pipe is secured to the manifold. Common for those fasteners to break, too. Any parts store in America can sell you a set of new studs and brass nuts. The brass nuts don't seize to the studs, so they can be removed without dynamite, later. Again, the tricky part is getting the rusty fasteners removed from the manifold. Sometimes, the manifold has to come off for "corrective surgery" to remove the rusted studs, repair the threaded holes, and replace with new studs/brass nuts.

Seven photos from my K1500 with Edelbrock "Stainless steel" headers with mild-steel flanges securing the donut. Flanges rusted away, no clamping force on the donut, exhaust leak cooked the donut. Not only did I have to dig-out the cooked donut with picks and tiny chisel, I had to figure out how to get flanges back onto this assembly.

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If you have all your bolt heads, and the donuts are not leaking, have someone run the engine ONE FOOT ON THE BRAKE (HARD!!!), ONE FOOT ON THE GAS, IN GEAR to load the engine, while you listen under the vehicle for the source of the ticking. Support the thing well, so it doesn't fall on you and kill you.

As a rule--generally but not always true--exhaust manifold work really sucks. The bolts are rusted, they break, they have to be drilled-out, they get drilled off-center, the holes they screw into get ruined and have to be repaired or replaced. It's bad enough at the donut flange, it's worse when you screw-up drilling a broken bolt out of the cylinder head.

Short story: This IS do-able, but go into the project mentally prepared to remove the intake manifold, pushrods, one or both cylinder heads; including allowing enough time and money for the extended project. That way, if things go "right" it's a relief that you didn't have to rip the engine down to the short-block, not a disappointment that you did have to pop the cylinder head(s) off.

PS. If that engine is running even close to "right", 2500-mile oil changes are not doing you any good. That oil is typically good for double that mileage, maybe more. I have an '03 Trailblazer that gets a fresh filter at 13,000 miles, the oil and filter gets changed at 26,000 miles. I top-off the oil as needed--typically better than a quart to 4000 miles. This vehicle only has 260,000 miles on it, so I don't know how this will work long-term. I've sent off oil samples to the lab at 26,000 miles, the results were that the oil was "fit for use".

 

[Schurkey]

[At the limit for photos in previous post]

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Note traces of anti-seize, and brass nut on flange.

The header side also got a split-flange just like this one, with bolts and brass nuts to connect the two sides of the donut together.

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[wezmykat]

Schurkey​

is right, I have a 1994 350 and the number 2 & 7 cylinders have a broken exhast manifold bolts, I can see the hot exhaust gas escaping from the manifold at those two locations as well as at the donuts (in very-very-cold weather) and it has the same slight sound when I'm doing 70mph but dont really hear it at other times, the truck runs just fine but the real solution for me is to remove the broken bolts, replace the manifolts and gaskets, new bolts, new donuts, it just does not bother me enough to do it yet, maybe next summer.

do you have a link where I can buy that split-flange?

 

[Schurkey]

do you have a link where I can buy that split-flange?

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www.amazon.com/Walker-Exhaust-36130-Flange-Repair/dp/B00G6UF26U

Make sure it's the diameter you need. A cast-iron manifold shouldn't need one, but the pipe attached to it might.

 

[Erik the Awful]

I change oil no more than 2500 miles and let it warm up.

I agree with Schurkey, you're throwing money away with religious 2500 mile oil changes. I aim to change my oil every 3000 miles, but it usually ends up being closer to 5000 miles. The fact that you're warming up your engine helps the oil last.

 

[reservoir dog]

When I bought my 94 3 yrs ago it had a bad ticking exhaust leak , mostly under load. I discovered the drivers side rearmost bolt was broken off even with the head. I removed the exhaust manifold and used Felpro foil gaskets and reinstalled , its been like that ever since and no leaks. I did not want to gamble drilling the hole off center, also did not have a right angle drill. Installed a new donut at the same time.