Glowing Exhaust manifolds

I have a 2004 Pontiac Grand Prix with the 3.8l supercharged engine. The car has been running hot so I drove it up a mountain road to get it hot and see if the fans were coming on (they were). When I opened the hood to check the fans I noticed that the exhaust manifolds were glowing red. I’ve read that this is bad in one article and that it is normal with the supercharger in another. What do you think?

I seriously doubt that red-hot exhaust manifolds are ever normal. Most of the time when a part of the exhaust system gets hot enough to glow like this, there’s a restriction somewhere. Does it have any other issues besides running hot, such as rough running or sputtering?

The car acts like it is vapor locking (surge).It only does it when climbing long mountain passes. other than then it runs great. I talked to my wife who drove it to Denver and she said the check engine light came on while it was surging. she took it to the dealer and had them scan it. An O2 sensor fault came up. Could that cause it?


A failed oxygen sensor would allow the engine to run rich, that is to say it would run with too much fuel. The excess fuel wouldn’t completely burn in the combustion chamber, it would continue to burn in the exhaust manifold.

This would, as you’ve seen, result in red hot exhaust components.

So it’s using more fuel than it should. That ought to be enough to prompt you to fix it. Then, of course there’s that whole “set the car on fire” thing, for another. ANY red hot ANYTHING under your hood is going to start a fire, sooner or later. I’d bet on sooner. And of course, even without the car burning to a crisp, you’re polluting the air.

If it was mine, I’d get it fixed today.

Often this is caused by a clogged or partially clogged catalytic converter. This could be tested very easily with a vacuum gauge.

Keep in mind that when the exhaust manifolds are glowing red this means the top end of your engine (heads, pistons, rings, etc.) is being barbecued. Right off the top of my head I’ve seen this problem several times. In one case the engine was mildly damaged and in the other the engine was totally wiped out.
In the latter case, even the paint on both sides of the hood was starting to blacken.

In both of these cases the converters were at fault.

Glowing exhausts are neat, install windows in your hood to show them off.

My motorbike (Triumph Bonneville) has glowing pipes. On that it is caused by the air injection system putting air into the exhaust at the exhaust valve location to burn off any unburnt hydrocarbons. No Cat converter. It works well and just holding the throttle at high idle is enough to make them glow in the dark. Looks good!

Does your grand prix have air injection?

Under high loads, exhaust headers can glow even when there’s no malfunction.
Check out this dyno run of a Honda F-1 engine.

It is NORMAL for a heavily loaded engine to have a red-hot exhaust manifold.

Many years ago I witnessed a motor oil test at Phillips Petroleum Company’s R&D lab. They had a 455 Olds engine at full throttle, 4000 RPM on a engine dyno. The exhaust manifolds were translucent! You could see the shadow of a stick passed behind them!

Those engines were run like that for 50 hours then torn down and examined for “excessive wear” or “impending failure”…

Wow! And, I thought it was marvelous to see the bones in the hand with a powerful light! Metal becoming translucent…!!

I second a clogged catalytic converter.

If I ever raise the hood on one of my cars and see even a hint of a glowing exhaust manifold the worry beads are going to start forming PDQ.

There is no way in the world that I will ever believe that glowing red manifolds are normal or healthy for the engine. If this car were mine I’d have the vacuum gauge on it in a heartbeat and depending on the results of that reading would follow it up with a compression test.

How long does anyone think plug wires would last on a 3.8 if this were considered normal? The plug wires are located right next to the manifolds and only have a metallic shield over the most confined ones. Even those shields are near pointless.

The surging is either a very lean condition brought on by the overheating or it’s pistons/piston rings trying to seize in the cylinder bores.

Headers would really freak you out. A 440 engine was good at lighting up the headers. I have noticed the red exhaust manifolds at night. Some will get red in the daytime but it’s hard to tell at first. Mountain roads should turn them red.

Could be as simple as bad timing. It may be normal…it may NOT be normal.

Agree; it sounds like your exhaust manifold has turned into an AFTERBURNER with the rich, unburned fuel combusting further after it leaves the engine. The same thing can happen to your catalytic converter which could set your floor carpets on fire. This happened to my brother-in-law’s Ford.

As mentioned by others, this is something you should have checked out right away and necessary repairs made.