Knocking/rattling at a red light

[navymaverick]

Howdy. I have a 1993 2WD Safari with 192,000 on it. I am not sure if this is a suspension issue or not but here it goes. It recently started a knocking noise while I sit at a red light. The knocking is very consistent with the engine speed (i.e. it times itself with the vibrations made naturally by the rotation of the engine). Now if I were to bump the transmission into neutral, it goes away. If I let off on the brake all the way, it goes away. It is a little bit harsher of a knock if I were facing downhill a it than facing uphill or on a level surface.

There is also a rattle while I am driving coming from (what seems to be) the driver side wheel well. It is not a loud rattle as I only hear it at low speed with my window down. It sounds like sheet metal that is loose or something. It does not shake the whole van like the knocking. The noise does not penetrate my firewall so I cannot hear at normal speeds or with my window up. I am not sure if the knocking and the rattling are associated in any way.

I have done a few adhoc visual inspections... whatever I can do in a parking lot. I can find nothing. Last Fall I put in new tie-rod ends on both sides. I followed instructions so they went in correctly. The visual inspections I have done confirm that these are working great. Also last Fall/Winter, I put in new brake calipers. Everything still appears to be working great on that end.

Any help or direction would be great. Thanks!

[grandamle91]

Sounds like a bad motor mount, and for the rattle my bumper used to hit the fender

[navymaverick]

Well, I did think about the motor mount but they appear intact.

[grandamle91]

Can you get some one to put it in gear and hold the brake so you can hear where the noise is coming from?

[navymaverick]

LOL, I can but do I trust anyone while I am looking under there? I will be lifting it later today and really getting down to diagnosing it. Since it is my daily driver I am reluctant to start taking it apart. I will try and get pic or at least more information about what I find.

[grandamle91]

Video would be better, if you can

[navymaverick]

I had nothing to take a picture of let alone a video. But after getting up under it while my brother stood on the brake while it was running and in gear, I noticed that the noise was coming from the torque converter area. I do not know what is making the noise. I appears that every connection between the motor and tranny is sound. Could it be the converter itself?

[grandamle91]

Check the bolts around the tranny and TC to flywheel bojjlts

[Jasen]

Yes or a cracked flex plate. You might have a trans shop take a look unless you cab do it yourself. The starter isn't lose is it.

[TDMobile]

Even though the motor mounts seem to look ok, isn't it possible that it's still worn? I thought I read that somewhere on here....?

[grandamle91]

Yea I've have ones the metal inside the rubber break lose and was moving around

[Shad0wXCalibur]

Just because the motor mounts look ok doesn't mean they are. Ask me how I know. At that mileage, I'd bet they need replacing.

[navymaverick]

Thanks all. I have a few leads now to go on. I will repost when I find the time to get back under it.

[navymaverick]

Well, I just now got out from under it. The motor mounts are all intact. All bolts are in and tight. From a visual side, the rubber in the motor mounts are still intact and complete. All-in-all I am pretty sure that they are not the issue.

I inspected the flywheel. About 8 years ago the tranny gave out and I got it replaced. The mechanic never re-installed the flywheel cover but that really is not an issue. By it not being on there it made inspection a breeze. The flywheel has no cracks and all the bolts are in it and snug. There is however a small piece of metal that surrounds one of the bolts. I was welded on during manufacturing. I believe it to be a balancing weight as the other two bolts on the flywheel are not surrounded by one of these.

To recap however, the rattle/knock/vibration is only present when the van is in gear, the brake is pressed and the van is at a total and complete stop. It is usually more apparent when facing downhill even slightly. Take away any one of these factors and it goes away. If I take my foot off the brake and start to roll forward, it goes away. If I bump it into neutral, it goes away. If I am moving slightly forward but with the brake mostly pressed, it goes mostly away.

Every other thing that I can imagine is structurally sound like the suspension, u-joints, mounts...

[TDMobile]

Maybe it's just the van having uncommonly high torque at idle?

[navymaverick]

It has always had high torque. I think it is normal. I barely let off on the brake and it takes off. It spins the back wheels pretty easily in snow. I fights against braking when I am slowing for a stop. So yeah, it has high low end torque. But it might be just what it was designed to do.

[navymaverick]

... reading other posts. As good as the ones i have in seem to look, I think the motor mounts might need replacing. I will get to them next week and tell you how it goes.

[356redux]

I had the exact same issue while going through my van. I replaced cap, rotor, plugs, ignition, etc, trying to get the motor to run smoothly. It ran like butter but shook like an epileptic while stopped in gear. It also got worse when i pressed harder on the brake pedal. Turned out it was my motor mounts. Both me and my friend looked at them on two separate occasions and we both concluded that they were ok. As it turned out it was in fact the motor mounts. Once I changed them the van is sooo smoooooth. I bet it's the motor mounts because my symptoms were exactly the same as yours. I have a 92 2wd by the way.

[navymaverick]

While going through my pics on my computer, I found these and forgot that I had said that I would post them. They are front and back views of my old motor mounts. The second pic is of further inspection from my master mechanic, Alley. The new ones took 4-5 hours to put in but took care of most of the issues. The van still wants to take off at a stop while still in gear. There is still high torque and a but of either power fluctuation (misfiring or something) or maybe a tranny issue. Something that is not very smooth while at a red light in gear. However, the whole thing does not shake and rattle any more as it did with the loose engine.