Heat Shields on Exhaust Manifold Loose and Rattling

[the_doctor]

I've got an '89 Lesabre with two loose heat shields on the exhaust manifold. Both the heat shield in the front of the engine and the one in the rear is loose. The one in the rear is very loose. I'm wondering how I can reattach them so they stop rattling. It appears, from looking at the front one that they are (were) riveted on. I was considering trying steel hose clamps to snug them up. Anybody try that? Would it be OK if I just remove them?
Thanks.

[yogi_123rd]

I have the same problem on my '90 lesaber as well as a few other cars I've had in the past.
The simplest thing is just to remove them rather than replace them.

The heat shield's function is to help bring the engine up to normal operating tempeature a little bit faster by retaining heat. They also act as a barrier for a mechanic who works on an uncooled engine and would inadvertantly touch a hot manifold.

[avatar307]

A lot of the heat sheilds function also has to do with protection for the car in my opinion. On the catalytic converter, the shield protects it from damage from rocks. On the engine exaust manifolds, they protect the manifolds from melting the rest of the car. My 95 also has a heat sheild near the main fan, mostly to deflect the heat from the termostat that turns the fan on and off. (As the fan should turn on in response to hot coolant, not the radiant heat from really, really hot exaust manifolds.)

My point being, heat shields do have a relationship to the everyday functions of your engine and automobile. They were put there on purpose by someone who probably knew what they were doing, so you shouldn't just cut them off.

(Strange how everyone I know is always cutting things off cars... and 50% replacing them with something that cost twice as much. -- I still haven't figured out why my brother thought it would be a good idea to climb under his new truck and cut off the entire exaust system. Now he wants to put it on because the engine is having issues, his fuel milage got worse, it loud, and smells. Can't though, because all he has is a little mig welder that won't do the job.)

As far as hose clamps... I'd be all for hose clamps. As long as you can attach them in such a way that does not change the orientation of the heat shield. That is, you can't wrap them around the heat sheild and press the heat sheild into contact with the manifold. There is a reason why there is a half-inch air space between the two, and you need to maintain whatever the original air space was.

I.e. Hose clamps around the mounting points only... and don't get them too tight, or they'll just break under the heat. Or crack your manifold... one of the two. LOL

[the_doctor]

Thanks for all your advice. I now have hose clamps snuging up both the front and rear exhaust manifold heat shields. Works great and easy to do. However my rattle is still there. I've replaced the belt and idler pulley, alternator (because it was bad), cat converter, and harmonic balancer. I still get a rattle at start up and when I shut it off. Oh well, the search continues . . .

[avatar307]

Hmm.... you only get the rattle when start and stop the engine? It doesn't rattle after the engine is started? Even if you open the hood, and hit the throttle, no rattle?

Kinda sounds to me like it might be doing that "blowback burnoff misfire" thing engines sometimes do when the PCV is busted. Might want to check it. All you have to do is remove the PCV valve and shake it, if it it rattles, it's good.

Any other ideas Yogi?

[3echo9]

Just wondering...are they loose due to a broken rivet head? I had some rattling along the exhaust system due to this and just knocked out the old and put in some new rivets and the rattles were gone....at least for now.

[avatar307]

*nod, nod* the_doctor stated that they appeared to originally be riveted on. I figured it was less work to just hose clamp them since they are on the engine manifolds. Riveting in those areas is kind difficult, nor do I really know how it's supposed to be done. Plus... if part of the rivet was still in there, you'd have to drill it out most likely... which probably means removing the manifolds.

One, it would be hard to get a drill in there. Two, yeah, you might be able to hit them with a punch and knock them inside the manifold. However, with both of those, you are almost certainly going to get metal shaving and fragments inside the manifold. Thus, they should be removed if doing it this way. Even if the rivets are already gone, I expect if you replaced them with the wrong type of rivets, the new rivets might break off and fall inside the manifold.

Metal getting in the exaust manifold just isn't a good idea. With high pressure exaust, these fragments are going to be blown out at a high velocity. If metal hits the O2 sensor, it's almost certainly busted. Likewise, metal fragments being blown into the Catalytic Converter would most certainly cause some level of damage. Plus, even though they are small, they could get stuck in the Cat or the Muffler, inhibiting exaust flow, and damaging engine performance.

So I recommended hose clamps. It's just easier and safer in my opinion. Provided you don't get them too extremely tight and crack the manifold.

[the_doctor]

It would have been extremely hard to get a drill in there to drill out the old rivets. Even if I could the holes in the heat shield were probably a little enlarged or corroded and a new rivet might not last long. The hose clamps are working great. Due to the characteristics of both the heat shield and hose clamps you really don't have to tighten the clamps up much before the whole thing is snug.

Avatar307 . . .I think you might be right about my rattle. It only does it at start up and shut down. For a while I thought it was my starter, but the fact that it also does it at shut down dismisses that. I have never checked the pcv valve. The last time it might have been checked was 75,000 miles ago. I'll check it out. . . .Thanks