Exhaust Manifold: Buy Online & Save!

Sure, here's the translation:

"Hi there," or "Good morning," (informal greeting)

In September 2013, the exhaust manifold on my Fiat 1.9 MJet 16V became warped and broke off a stud. It was then machined (3 mm were removed) and reinstalled with new gaskets. For three whole weeks, everything was fine, but then the smell returned, although nothing was visible. Now, after 8 months, it's protruding about 5 mm near the first cylinder and is also whistling loudly from that area.

It's not possible to re-plan the exhaust manifold now, as the studs would then be too short. A new one costs €1000 (including installation) from the official dealer (€690 for the manifold itself with a 12% discount). Through research, we found a wholesaler that offers OEM parts for €520. Why did the planned exhaust manifold warp again? Did we overlook something?

The car is 6.5 years old, has 123,000 kilometers on the odometer, and we hope it will last us for a few more years.

Quote:

Why did the planned manifold warp again

Because the engine is running too lean and the exhaust temperature is too high?

Hi,

The EDC (Electronic Diesel Control) system has been checked, and the fuel injection amounts, air intake amounts, and temperatures are all within the acceptable range. The engine was also available without a DPF (Diesel Particulate Filter), which leads me to suspect that the material used in the DPF is not able to withstand the high temperatures during the regeneration process.

dokky wrote:

Hi, EDC has been reviewed...

Okay, I dozed off and missed that it's a diesel. I'm more familiar with warped exhaust manifolds on gasoline engines.

In diesel engines, excessively high exhaust temperatures can be caused by poor tuning (injection timing that is too late) and a lack of air.
That is to say, even in its standard condition, an excessively large leak in the charge air duct could cause the engine, and particularly the cylinder head and exhaust system, to overheat when driving at high speed on the highway.

Given that leak detection can be complex depending on the vehicle, I would suggest finding an identical vehicle that is in good working order and comparing the air mass readings displayed by the engine control unit under high load and similar conditions.

Air mass is the same: the error lies elsewhere.
Air mass sensor reading is normal, but the vehicle is smaller: The other vehicle has a leak in the charge air system. Check the pipes and intercooler for oil traces.
Air mass reading higher than expected: Check the other vehicle for restrictions or blockages in the intake or exhaust system.

Best regards, Rainer.

Okay, thanks for the information. The intercooler system is likely sealed, since the mass airflow sensor (MAF) was recently replaced. Just to be safe, I'll look for a comparable engine and log the data. The exhaust readings might also provide some insights into the combustion process, right? It's a quick check.


My suspicion is that it's a design flaw, as the screw arrangement around the first cylinder on the cylinder head is poorly chosen, and also, with the turbocharger and catalytic converter attached, there's quite a bit of weight on it. I just don't want to waste another 4-6 hours and 600 euros.

When you search on Google, you'll find that many Alfa Romeos and Opel 1.9 CDTI engines (which are almost identical) also have this problem, and it's very expensive to fix at Opel because the turbocharger is directly mounted to the exhaust manifold.

Quote:

Emission values could also provide insights into the combustion process, right?

However, these measurements are usually not taken when driving at full throttle on the highway.

Grinding off 3mm is quite a significant amount and doesn't necessarily make the manifold more stable or rigid.
Otherwise, I would say that the component was not tightened sufficiently and/or old studs were used.

With those 25 Nm, like in the Polo 6N, you won't achieve much.
It's more like regular spark plugs - tighten them by feel until the seal is just starting to compress.

"I always use new studs from VW and ensure they are securely fastened in multiple stages."

With a large gap, you might need a "spacer" and two gaskets between the protruding manifold section and the cylinder head. With a small gap, it might be possible to use just two gaskets.
hg
Herbert.

I'm leaning towards replacing the part entirely, even if you can temporarily fix it with seals. You never know if it will warp further. It's been planned for before...

We used completely new gaskets, studs, and nuts, and tightened them with more than 25 Nm. After each DPF cleaning, the problem gets worse.

Ich habe jetzt den Injektor am ersten Zylinder prüfen lassen. No findings.

We reluctantly ordered a new exhaust manifold, including bolts and gaskets. It will be installed on Friday.

Hi everyone,

The new manifold is installed. It still smells a bit, but that's normal as everything needs to settle. You could clearly see on the old gasket that it was leaking significantly on the first and third cylinders.

Let's see if things will finally be quiet now.

Thank you for the feedback .

Tip: Tighten the screws again, if necessary.

Hi,

I've tightened it three times. It still has a slight smell, but I was told that it might linger for a few more days. However, it's nothing like it was before.

Hi,

The problem seems to be solved. There is no more smell. Yesterday, he cleaned the DPF for almost 20 minutes, and it was done without any odor.

Thank you for the feedback!

"Too early to celebrate."

After a week and 2000 km, this morning, right after starting, it briefly made a whistling sound from the engine compartment. Then, while waiting at a red light today, I smelled something again coming from the ventilation system. I opened the cover, and it smells bad again at the first cylinder.

Could the head be warped? I can rule out the DPF and catalytic converter, the engine is running at its maximum speed.