03' Civic with cracked Exhaust Manifold (PO325)

[Chrisfromalbany]

I have a friend with 03' Civic w/158K cracked exhaust manifold and recently had check engine light on for PO325 (Knock Sensor). I believe the manifold has been cracked for awhile. Can a crack in the manifold cause a knock in the engine. The quote for the repair was $1.6K for parts and labor and replacing a catalytic converter . Does that seem reasonable for the work? I figure it is, just thought I would ask. I also wondering if the crack is fixed (aka replaced manifold) will that for sure make engine knock to go away. As sure as you can be with anything. I don't believe there any other codes on car besides a (P1298 –ELD Voltage Low).

The owner of the car at the point where wondering if they shouldn't just sell the car.

Thanks,

Chris

 

[eljefino]

With the money at stake I'd want to look at the live data and see if it's pulling timing at idle etc.

Are you insinuating that the cracked manifold might be ignored if the knock sensor code were otherwise somehow cured?

 

[Chrisfromalbany]

Originally Posted By: eljefino
With the money at stake I'd want to look at the live data and see if it's pulling timing at idle etc.

Are you insinuating that the cracked manifold might be ignored if the knock sensor code were otherwise somehow cured?


I didn't know a crack manifold would cause a knock issue. I had a cracked exhaust manifold with Jeep Grand and never did. So I was wondering.

 

[Chrisfromalbany]

Any other thoughts/ideas and whether they keep the car or sell it? The car does have a few accidents on the carfax.

Thanks,

Chris

 

[supton]

With a few accidents on carfax, 158k on the clock and being 10 years old, it's not worth a lot. At the same time, if it's not rusty, it should have plenty of life left in it. An exhaust manifold is pricey, but still cheaper than a new car, and less dicey than a used one.

I'd think if the manifold was badly cracked it might cause the sensor to read improperly. I wouldn't think so. Could be a secondary issue.

 

[Chrisfromalbany]

so you are saying the knock sensor more then likely isn't being causing by the manifold crack? That is what I was thinking but I wanted a few more opinions.

 

[Trav]

A lot of things can trigger the knock sensor off. On some BMW V12's for example it was common they would be triggered by water pump noise and they would drop power like crazy.
It seems almost anything is possible.

 

[Chrisfromalbany]

Originally Posted By: Trav
A lot of things can trigger the knock sensor off. On some BMW V12's for example it was common they would be triggered by water pump noise and they would drop power like crazy.
It seems almost anything is possible.


Almost like keep driving the car and see if it happens again.

 

[user52165]

Yes, a cracked manifold can cause a knock sensor code. Yes, this car is worth fixing. Hit the junkyards - not difficult to install manifold or expensive to buy. Lots out there. Don't spend $1600. That is a high quote caused by the cat can price. Is it really needed?

Check with a welder. If the crack is easily accessible, perhaps it can be fixed on the car.

 

[Chrisfromalbany]

Originally Posted By: user52165
Yes, a cracked manifold can cause a knock sensor code. Yes, this car is worth fixing. Hit the junkyards - not difficult to install manifold or expensive to buy. Lots out there. Don't spend $1600. That is a high quote caused by the cat can price. Is it really needed?

Check with a welder. If the crack is easily accessible, perhaps it can be fixed on the car.


So saying I look at getting a used intake manifold so save money on the project? Is the cat really needed you are asking?

 

[supton]

Won't pass OBDII inspection w/o it. Don't know if you can salvage it out of the manifold or not.

 

[bepperb]

I'd find a boneyard mani-cat and diy, or pay a shop hourly to do it. I bet new they are 1000+, but I bet a used one could be found for half or less. Another option would be an aftermarket one, the reputation for those is terrible but it could buy a year or two or more for only a couple hundred bucks.

And yes, I can see how it could trigger the knock sensor.

 

[Tegger]

Originally Posted By: Chrisfromalbany
I have a friend with 03' Civic w/158K cracked exhaust manifold and recently had check engine light on for PO325 (Knock Sensor). I believe the manifold has been cracked for awhile. Can a crack in the manifold cause a knock in the engine.

I suppose it's possible, but it won't cause a P0325. P0325 is an electrical code: You have an open or some other wiring issue, or the knock sensor is electrically defective. Clear the codes (write them down first!), and see if the P0325 comes back. It might not.

Originally Posted By: Chrisfromalbany
The quote for the repair was $1.6K for parts and labor and replacing a catalytic converter . Does that seem reasonable for the work?

Why are they replacing the cat? If your engine is one of those where the cat is integral with the exhaust manifold, then I can understand. If it's one where the manifold is bolted to the cat, then there should be no need to replace the cat unless you're getting a P0420.

Junkyard manifolds are a gamble. If this engine has a history of cracking manifolds (I don't think it does), then any other used manifold you get may crack as well.

Originally Posted By: Chrisfromalbany
I don't believe there any other codes on car besides a (P1298 –ELD Voltage Low).

Better make certain of that. If the garage pulls the codes for you, insist that they write them down for you before clearing them.

And my charts say that P1298 is for HIGH voltage in the ELD, not LOW. Low is P1297.

 

[ARB1977]

I would by a aftermarket performance header.

 

[surfstar]

Originally Posted By: ARB1977
I would by a aftermarket performance header.


x2
perfect excuse to upgrade and a good one should be $300 tops w/ ebay [censored] ones starting arond $100 I'd wager.

 

[jegs]

Bad motor mounts can cause cracked exhaust manifolds. Might want to check them out since it is an older car.

 

[MarkM66]

$1600 for a cracked manifold. Please...

They're stainless, and can easily be welded. Or buy a used one off ebay and change it.

 

[user52165]

Originally Posted By: Chrisfromalbany
Originally Posted By: user52165
Yes, a cracked manifold can cause a knock sensor code. Yes, this car is worth fixing. Hit the junkyards - not difficult to install manifold or expensive to buy. Lots out there. Don't spend $1600. That is a high quote caused by the cat can price. Is it really needed?

Check with a welder. If the crack is easily accessible, perhaps it can be fixed on the car.


So saying I look at getting a used intake manifold so save money on the project? Is the cat really needed you are asking?


I hope you mean exhaust as in OP?

 

[Kestas]

I had an exhaust engineer explain to me that a small leak in the exhaust system can easily mess up an O2 sensor. Pulsations from the exhaust can slurp air into the exhaust stream between pulses, and the O2 sensor will react to this air.

If the cat is integral with the manifold, it may be nearly impossible to find a salvage part. I believe it is still illegal to sell used catalytic converters.

Welding stainless can be easy, depending on the material. 409 ss will weld easily. 300-series ss is more difficult to weld.

With all said, I believe weld repair is the way to go. I assume the manifold is otherwise healthy and not rotting away.