Jeepjosh

I just bought a diesel Jeep that the owner said has a blown exhaust gasket. It does sound like that, it's the same sound you get if you take one plug out of a 4 cylinder petrol engine and run it. A chuff, chuff noise.

Oddly, I noticed when driving it with my foot off the clutch pedal, the sound diminishes a lot, yet if I rest my foot on the pedal as if about to change gear, the noise appears again loudly.

With the gearbox in neutral, the sound is the same whether the pedal is depressed or not - loud.

Too dark for me to look now, but I don't know how the clutch and exhaust would be connected, except for some servo assistance as it is a hydraulic clutch maybe.

The clutch does feel kind of heavy, so is there a connection???

JeepingDan

Maybe with the twisting of the motor your exaust makes the leak bigger.

farmfuel

Does the engine run like it has a miss? You can crack the injector lines to produce a missfire. If you did have a missfire, then injector line that you crack open; the RPM wouldn't fluctuate. It'd be the same principle as removing each plug wire on a gasser, until you find the miss

They don't sell the diesel Cherokee over here in the States, so few would have knowledge of that engine...Renualt, right? Is it turbocharged? I can't imagine the manifold gasket being all that hard to change out, although I've never seen that engine. I don't think I've ever seen a turbo manifold that was leaking at the turbo flange. Perhaps the mainfold is cracked as well? Cast does crack.

Ya'll are so lucky to have the diesel power that you do. The only diesels over here are in 3/4 and 1 ton trucks...and a couple of VW's. We're at the mercy of greedy oil speculators who bid into oil futures because of reports that the economy "may" be getting better. ...bastards

The price of oil goes up by dollars, but recedes by cents...ridiculous. If we had diesels galore like ya'll do; some of us may actually be able to AFFORD to drive to work.

Jeepjosh

Hi itzdan and farmfuel, thanks for your replies.
The diesel engine in these Jeeps is a 138 BHP Italian VM engine, originally designed as a marine engine, although I think it's actually 114BHP. It's the same lump as is in a 2.5 Range Rover. It's turbocharged and should provide the kind of torque and mileage I am after, without costing loads at the pumps.

The engine doesn't run like it's missing, just has this really loud chuff, chuff noise in time with combustion of one cylinder I imagine. Outside the car, the noise is worse, a loud clap, clap accompanies the chuff, chuff noise.

It can't be doing the power or the engine any good really, so I will get it fixed as soon as I can and report back what it was, in case the subject comes up again.

The gasket shouldn't be hard to fix and I am gonna get it looked at in the next 2 days, but just trying to get a handle on why the clutch has any part to play in the noise at all.

farmfuel

I wonder if this noise that you're hearing is coming from the pressure plate, or perhaps the throwout bearing. If one of the bands on the pressure plate is broke, or if one of the little fingers is bent, then you'd be experiencing a stiff pedal, and perhaps a noise would emit from the assembly once the throwout bearing meets the fingers on the pressure plate. If you rest your foot on the pedal, you're sending the throwout bearing into the fingers of the pressure plate. The throwout bearing is just that, a thrust bearing. Usually they just get dry, and begin to sound like a washing machine. a dry bearing sound. A way to see if your noise is emmiting from the bellhousing area would be to get under the transmission, have someone depress the clutch pedal while you're under it- and see if you can hear a change in the noise that it's emmiting.

Maybe you can send a picture of the exhaust manifold? You could have two seperate problems.

Jeepjosh

It's definately much louder than any noise from a mechanical source such as the clutch assembly. If you stand in front of the engine bay with the bonnet up, it is quite deafening. I'm sure it's the sound of combustion leaking through a gasket or a cracked manifold.

I can't even see where it's coming from, there is so much in the way on these lumps. Sounds like toward the back of the engine, on the exhaust side though.

It may be 2 different issues, as you say, but really odd why the position of the pedal has anything to do with it and only when the car is in motion, not when it's just idling.

It's a pain in the a*se, as I want to just get on and drive the bloody thing now I've bought it!

JeepingDan

Diesel Xj's are new to me. I've never seen one around my area yet. But yea maybe it's a cracked manifold or blown gasket.

Jeepjosh

I found a receipt in the car from a garage so called it in case it was the one that serviced the Jeep before me. It was and he remembered that he thought the small gasket from the manifold to turbo could be blowing or maybe the manifold was cracked. If it's the former, it's a cheap fix, if the latter, that means a new manifold probably if it can't be patched. Get the oil pressure sensor fixed at the same time, sorted.

Here's to a cheap fix then. I'll let you you.

fantic238

You're lucky. I work for a company that marinizes the VM engines and i am Italian.
It's the VM motori 2.5 turbo with separate heads. Same as Chrysler voyager, range rover, grand cherokee, jeep JK, london taxi, alfa romeo 164 etc..
Probably one of the exhaust gaskets is shot. If you have also a power loss then the manifold is cracked near the turbo. It's a great engine, reliable and strong but it doesn't like overheating. Timing gears are indestructible just like the old perkins. Like you said it's a marine engine and it was designed to work at 70° celsius. Automotive application is around 90° celsius and when you overheat due to bad mainteinance of the cooling system things start to crack.
The reason because you don't hear the loud chuff when you step off the pedal is because it's a DIESEL. When you close the gas you cut the fuel to the cylinders and you have no combustion aka no noise.
Let me know if you need diagrams, torque specs etc.

dyte2004

you could always convert to propane its far cheaper and more fun

Jeepjosh

@Fantic238

Thanks for your reply and I'm glad that you understand these engines!

Just a note, the pedal I refer to is the clutch pedal, not the accelarator which is why I thought it odd that the action of this pedal had anything to do with the noise.
I have found that when outside the cabin it doesn't make a difference to the noise, so I think the clutch rod bulkhead grommet may be worn and when i depress the pedal or even rest on it, the noise from the engine bay comes through to the cabin.

But yes, if you have any Jeep relevant diagrams that would be really useful. I have downloaded some, but they seem to be slightly different models to the VM in the Jeep.

A couple of mechanics have assesed the problem as probably exhaust gasket, however they cannot tell which one. It could even be the gasket that joins the turbo to the manifold or the gasket that joins the downpipe to the turbo. Upon starting, a puff of smoke comes up from the back of the engine, manifold area.

I think it could even be around the manifold to block area, as I trickled some water there while the engine was going and it spat back splashes of water between the waterway and the block. I am not sure why though, as there isn't a gasket there?

I am going to lift the rocker cover today and see if I can see anything. The cover is not very well sealed as there are a a couple of areas where oil is dripping out and also between a couple of heads there is oil spraying slightly. It better not be coming from the heads!!

If you have the correct torques for tightening the rocker cover back up, that would be good.