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'97 Quad 4 Knocking

Farmer Joe
08-21-2005, 07:00 AM
I have a '97 GA 2.4 Quad 4 and the engine is knocking while running, more like a rapping. It seems to be coming from the head and under the front cam. The power steering pump is directly driven off of that cam too. I can feel the rapping when I put my hand on the power steering pump. To me it doesn't sound like a rod knock, that would be a deeper sound and be lower in the engine. This sounds like its in the head near the power steering pump. It does become intermittent during a cold idle and when you rev the engine up past 2500 rpm. It does get louder and stronger sounding the warmer the engine becomes. Oil pressure and temp are all normal during operation and according to the former owner its been doing this for the last 1200 miles and not getting worse. Do these twin cam engines have lifters like old v-8s? I could compare this sound to bad lifters in a small block Chevy. A couple other things to consider. The former owner had the power steering pump go dry from a broken line. It still holds fluid now and the steering seems fine. Also on this 2.4 engine, they had new injectors and fuel rail installed. He gave no reason why that was done.

I got the car cheap knowing that there was the engine noise, so either I'm a sucker for a GA or I love a challenge. Looking forward to any help that can be offered. BTW the local wrecking yard has another Quad 4 to sell me if I need it. Hopefully I can fix what I have.

Thanks again,

08-21-2005, 08:58 AM
Based on your description of the problem it sounds like you are experiencing piston slap. This usually occurs when one of the cylinders and piston become out of round due to wear. As for being able to feel it in the power steering pump this is just a transfer of noise/vibration due to the area where the noise is coming from. The only way you will be able to find out for sure is to tear the engine down to get to the source.

The reason it gets louder is due to expansion when the car warms up. The piston and cylinder expand due to heat and the tolerances get slightly larger thus increasing the noise.

These engines do have lifters but they are totally different than the ones you see in a non-overhead cam engine. If they make noise they sound like lifters tapping not a knock.

I hope I answered all your questions.

Farmer Joe
08-21-2005, 09:38 AM
Thanks for the reply. Piston slap, hmmmm. My 2002 GMC Sierra has that when its cold, and GM says that its OK. I doubt that its OK on this Quad 4 though. All the vital signs are good. It has power, no skipping or misfiring. Doesn't burn oil or lose coolant. I have not done a compression check yet. For me, it may be worth it to just go and get another Quad 4. Rebuilding the current one may take more time and cash than I want to spend on the car. I can always rebuild the one I take out at a later date. The local yard wants $300 for a used one, plus my time changing it out. I've never pulled an engine on a front driver before. Can I pull just the engine from the top or does it have to drop out of the bottom along with the trans axle? All that work I've done on old Chevys, but no late model experience.


Farmer Joe
08-21-2005, 10:12 AM
Was just out running this thing. The noise it makes standing outside the car is more of a "snapping" sound similar to an exhaust leak at the manifold. At the engine, its a loud tick with the occasional rattling and quiet moments. Like in my previous post no misfires, 40psi oil pressure. I'm kind of hoping it to be in the valve train but am not ruling out pistons. Maybe I'll just have to pull the cover for the cam and have a peek. Anything to be careful of doing that?

Thanks again,

08-21-2005, 12:09 PM
The bolts that hold the cam cover on also hold the cam housing on, so if you pull that cover you are going to have an oil leak when you tighten it. A used quad for $300? Check the mileage on it and insist on hearing it run, thats really cheap for the motor, out here in nh they are going for around $800 for high mileage, $1200 for low mileage. And unfortunately they do have to come out of the bottom of the car. If you are pulling one out of a wreck, cut everything around the top of the motor: fuel lines, wiring, hoses, etc. just to make it easier, drop the top motor mount on the pass. side of the car, use an engine support to hold the motor up, unbolt the strut mount at the top of the car, have the yard lift the car with a forklift so you can get under it, unbolt everything: engine cradle, torque strut, exhaust, lower radiator hose if you didint' get to it before, also disoonnect the tie rod ends from the steering knuckle. Once everything is disconnected, have them lower the car, remove the engine support, lift the car and drag the motor and trans away from the car and separate them. Good luck, its alot of work.

08-21-2005, 12:10 PM
could have some bearing damage in the cam area making noise. If it was ever ran low on oil or without oil, sure could've burnt some bearings or even spun one. I'd take the head off check the valves , they could be sticking. Hope this helps u out.

08-31-2005, 11:10 PM
I've had the same problem. I spun a rod bearing and elected to rebuild it myself and it totalled almost $1500 to rebuild it.

09-01-2005, 01:36 AM
used 2000 Quad "T" engine w/assessories still strapped on:
$650. w/ $50. core and 74K on the odom.
(pulled AND delivered) in houston.

the 2.4L can come out the top, but it is easier to drop the K-frame with everything. if you elect to separate eng/trans, have it jacked-up (naturally, and on stands), and you can still pull from the top with the front lifted; just need a friend to give the hood an extra "humph" for the 1/2-3/4" extra clearance, or the engine hoist is cleaving the front lip of the hood.
if you are looking for extra components, just watch exhausts slightly differed pre-95/6, 97-00 is same, but '00 you will have to reuse your injectors and rail (elec plugs differ), and you'll re-use your knock sensor, but have to re-thread it first (as 99/00 split and knock sensor on newer models almost half the size, but same connector).

hope this helps,
nrt racing

09-01-2005, 01:48 AM
and GTP Dad definitely knows his Poncho's, so piston slap sounds right on, as far as GM goes, but you might just unbolt the p/s pump (without unhooking the lines), and see if that plug that runs the pump off the cam is sheared, and just catching by RPM so steering doens't feel bad, or if the cam is rounding out.
taking the serp.belt off, and the pump would definitely isolate it as an internal problem.
I've also seen on GAs and GPs the "donut" or exhaust flanged gasket
between the exhaust manifold and pipe, deteriorate, create a leak, and vibration/knock. (this was mostly in the 3800s)
just hoping for you...
hate to see an engine yanked, if not necessary...
good luck.

09-01-2005, 05:31 AM
The items ctesla mentioned are certainly a possibility. Since it is extremely hard to diagnose an engine problem without being able to hear or see what is looks and sounds like try everything before actually pulling the engine. It is entirely possible that you have an exhaust leak causing this issue.

Have someone hold a rag over the end of the exhaust to block it. If there is a leak you should hear it and see it readily. If the engine slows down or dies then it is not the exhaust. If it is a leaking gasket it should get louder. Good Luck!

Farmer Joe
09-01-2005, 09:15 PM
Thanks for the additional input. I've finally had a chance to dig into this engine. I've isolated the noise to the intake valve train, number 3 cylinder. Pulled the intake cam and lifters and found one of the number 3 lifters worn a little more than the rest. Not by much. Its wear pattern from the cam differs from the rest It has a depression where the valve contacts and its barely noticable unless you run your fingernail over it. (couple thousandths?) The others are still smooth. Also this lifter's piston spins easier than the others. I was able to closly duplicate the noise by lightly tapping the lifter on the valve. The head and valves appear fine. No broken springs, or valve retainers. All valves are the same height on the head, so there should be nothing bent or stuck. I measured the cam lobes and they are all the same height. I blew air thru the cam housing oil line and its clear. I'm going to flush it anyways to clear any debris. I don't plan on pulling the head.

Now to find a set of lifters. Local Auto Zone doesn't have them, have to order. Going to call around tomorrow. Hopefully I've found the problem. I'll post when I'm finished.

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