Very loud bangs coming from the engine - diesel

[xj25vm]

Hello all,

The other week I went to start my stock XJ diesel '97 (I only use it rarely) - and the engine starting making this really loud metallic banging noises (but it was running). By the timing of the bangs, it was like some of the cylinders were doing their normal stuff, but one has gone crazy. Also, the whole engine is shaking uncontrollably.

I guess I don't need to ask about this one - it must be serious. What I wanted to know is if there is any way of guessing which part has gone. My suspicion is that the engine needs stripping before a diagnostic - am I wrong?

Also - any sort of advice on the matter - such as feasibility of repair, if it is worth doing etc. - much appreciated.

[Deezelweazel]

did you rev the engine lately?
sounds like a jumped out valve push rod.
mileage?

[xj25vm]

I've had the jeep since 2007 - and probably have done less than 2000 miles on it (in UK). Most of the time I've been working on replacing shock absorbers, exhaust manifold, flushing the radiator, replacing all fluids, filters and other maintenance. It is not my main car - it is my "impractical" car :-)

Most recently been sitting outside for about 1 year. Then in October this year it passed the safety test (MOT in the UK) - and I must have driven it about 20 miles in all. No hard revving - probably nothing above 35mph. There might have been a bit of revving involved during the MOT test - I think they do it to test the exhaust emissions. But that is not under load.

The clock shows 66000 miles - but I looked through paperwork - and my guess is that it's closer to 100000 miles. One of the previous owners must have been up to something, because the paperwork doesn't add up. Don't know much about the maintenance history - but looking at it's state - I don't think it's had much love - so we can expect the worst.

The good thing is that the engine appears to be in surprisingly good condition. It never, ever smokes when starting - even in the winter. It always starts on first key - even after sitting for a whole year untouched. It's one of the main reasons I just couldn't bring myself to parting with it. That and the fact it is an XJ :-)

Thanks for any hints

[rastus2571]

By the sound of it and the compression ratio on a diesel engine (Average 30:1) compared to a petrol engine(14:1) ball park figures and not to be gospel with valve clearances, you would have locked a valve straight away and had a seized engine.

You said:

The other week I went to start my stock XJ diesel '97 (I only use it rarely) - and the engine starting making this really loud metallic banging noises (but it was running). By the timing of the bangs, it was like some of the cylinders were doing their normal stuff, but one has gone crazy. Also, the whole engine is shaking uncontrollably.

I guess I don't need to ask about this one - it must be serious. What I wanted to know is if there is any way of guessing which part has gone. My suspicion is that the engine needs stripping before a diagnostic - am I wrong?

At the moment I would be looking at getting a compression test and a injector test done on it. You may have a seized injector from lack of use this does happen on diesels. Isolate the cylinder due to either compression or fuel flow on the injector. As i said when a diesel seizes it seizes full stop lock stock and barrel. NO GO MATE.

If you have an injector sieze the piston has nothing to compress against on the compression stroke and it will bang and fart as it is not getting fuel to compress however it will run fine on the other cylinders.

What is going on is that you have an uneven firing order with compression. # cylinders are firing and the dud one is not so this will go bang,bang,dud,bang and run rough as, Get a compression check and flow check done on the engine.
Try that and get back to me.

[xj25vm]

Thank you rastus2571. I'm not sure I understand one part: if the engine is seized - how come it is still turning over and firing up?

The other thing is - I would agree in principle with the bit about seized injector because of not being used for a long period of time. But this happened after I used it for few days (after the MOT test). I actually used it for few miles the night before, came home, parked it up - and when I went in the morning to start it - the loud bangs first started. Wouldn't a seized injector manifest itself after a period of no use - not few hours after using it last?

Thanks again for replying.

[Deezelweazel]

Nope- a failed injector sounds different. Worn Hydraulic valve tappet or jumped out valve rod.
Open the valve cover and inspect the 8 push rods and the levers.
Report back.

This engine can't seize if you drive with enough oil. tappets get noisy if you drive with to much or less oil.
The push rod can jump out easily- this is a banging sound if knocking somewhere.

A seized injector includes working valves and lots of white smoke. Because valves are still opening and closing.

A jumpped out push rod causes constant closed intake or exhaust valve.
no intake- no combustion at all
no exhaust- heavy knock

[xj25vm]

OK - thanks for that. I'll open up the valve cover and report back. It might take a while though - as I work on the Jeep when I get some spare time, and when it doesn't rain too hard :-)

Thanks again

[glend]

If you are in the UK (where it is cold right now) I might have a look at the glow plugs as it sounds like maybe one is not working at startup. That could account for your symptoms. That fact that it turns over and tries to run is a good indication that all is not lost. Secondly, bleed the air from the fuel system. Thirdly, get a good diesel mechanic to look it over.

[xj25vm]

Hi and thanks for replying. As I originally posted, the engine actually starts - not just turns over. It runs - it just that the noises it makes are so great - that I switched it off immediately - worrying that it might break something. The noises are loud and metallic - like a part is hitting something - so I'm not sure about just a glow plug not working.

I guess we will find out soon enough when I take the valve cover off.

[Deezelweazel]

non working glow plug - white smoke while start then diminishing to no sound and normal engine run...

[rastus2571]

I did think about this after you posted Deazeel Weazeel, Good call. Might be a stuck lifter as the pushrod would be banging harder than a you know what.

[rastus2571]

OK - thanks for that. I'll open up the valve cover and report back. It might take a while though - as I work on the Jeep when I get some spare time, and when it doesn't rain too hard :-)

Thanks again

Take the valve cover off, remove the injectors and get a long ratchet with the correct sized socket on the crank and
turn it clockwise (direction of rotation) and look at what each and every valve is doing, Are they all opening and closing porperly or not. If they are we have to delve a bit further. If not then you will be able to determine which one is not opening or closing properly as Deazeel Weezeal said.
Get back to us mate.

[Deezelweazel]

Oh, oh, oh removing the injectors is not that easy -they can be stuck!
You need a 28mm nut with no chamfer. the hex on the injector is only 3mm wide- if you use a nut with a chamfer you won't be able to loosen them. Risk of rounding off the injector hex.

Use a propane torch to heat up the heads carefully. Then give it a try.
You will need a 41mm nut to turn the crank. But you can't see the valves operating, due to the hydraulic tappet. A faulty tappet will be a problem.

Instead of this get the glowplugs out and screw in a 10mm thread with air from the compressor. You will be able to listen if the valves are closed or open.
No opening faulty hyd. tappet, or jumped out push rod.

[xj25vm]

Just a quick question about removing the cylinder head cover. My manual indicates that for RHD models, I have to empty the cooling system. Is there any trick to avoid this, or it just has to be done?

I think they should have called the RHD model "The Atoner" - it certainly feels like atoning for one's sins when working on it - the way they helpfully "re-arranged" the engine compartment.

I just thought I'd check.

[Evert]

Empty the coolant system when removing the head cover? No way man. Just ondo the 4 bolts and pull the thing off.

[xj25vm]

Hi Deezelweazel and all,

I've managed to take the head cover off today and indeed, the last pushrod towards the windscreen is out of the rocker arm. After I place it back in its place (assuming I will be able to just rotate the engine slowly with a wrench and then push it back in) - how do I stop it from popping out again?

Thank you

PS - No matter how much I pushed up the two cooling system pipes crossing over the cylinder head cover, I just couldn't create enough clearance to lift off and away the cover. In the end I had to disconnect them and loose some coolant. It looks like they are taking heated coolant to the cabin space heater.

[Easy Rollins 1]

Roll the pushrod on a flat surface to check for straightness.After refitting turn over the engine by hand to make sure all the valves are opening and closing OK.A bent or siezed valve stem(now jambed) could be the reason it threw a pushrod etc.Also a lazy or siezed hyd lifter could have given room for the rod to kick out.

HTH

[rastus2571]

Any chance of a pic mate?

4 things open the valves and 1 thing closes the valves.

I will give possible scenarios to each number.

1/ The cam lobe. This is where the lifter runs on. (maybe very worn). Unlikely you have a snapped camshaft,but however it may be possible. Way to check remove problem pushrod and rotate engine via crank with socket and breaker bar and check operation of other valves.

2/ The aforementioned lifter.Maybe collapsed/seized. Only way to check is to remove lifter and examine.Full of gunk,burnished,worn right out.


3/ The pushrod. Bent,snapped, bottom or top balls damaged.


4/ The rocker arm. Lash adjuster broken,loose,pushrod pivot on rocker worn,lash adjuster tip that sits on top of valve damaged,broken,rocker snapped.

5/The valve springs close the valve.collapsed,broken,collets on top of valve broken,stem of valve protuding above collet seat and valve hat.

Now if any of these are broken or not working properly we have none or very poor valve operation.

Are the springs on the valve closing the valve fully?

IE: Space between the valve springs and you cannot push it with your thumb down in anyway.

Are the collets that hold the valve cap to the valve stem still there?

Does anything else look unusual (apart from the pushrod loose)?

Is the rocker arm just flopping around? I am sure it is if you say the pushrod is out.

Is it broken? Look at my faults above.

See if you can gives us a pic mate. It really would help us.

Have a look at this to give yourself a better idea of how things work. It will give you a frame of mind of maybe to nail this beasty problem down.

http://auto.howstuffworks.com/engine4.htm

It is very hard diagnosing things over the internet with actually seeing the vehicle.

What you say now is definitely valve train related.

Pushrods just don't jump out or go loose when everything is working ok.

[Deezelweazel]

Pushrods just don't jump out or go loose when everything is working ok.

Oh yes, they do!
There are several causes for that.

[rastus2571]

Ok do tell then...HOW?

You got me real intrigued then on this one.

Over revving and abuse yes I agree. Does not seem the case in this problem.

Must be millions of cars popping pushrods all over the world when everything is working fine in the engine then....:o

Geez, the manufacturers must be flat out on warranty claims then.

I am trying to help this bloke out. If I didn't care I would not answer....How about some more input from you then DeeazeelWeeazeel instead of being critical on my posts? I post a lot on here helping.

I don't have to. I do it because I want to help and enjoy it and relax at the same time giving experience and help to those less fortunate knowing that we know.

Strange as it may seem I do know what I am talking about. I was an Australian Army heavy vehicle mechanic and civvy mechanic.

Enough of the banter. Let's be positive helping this chap out.:D

This guy needs help so let's help him.

You can take it over from here on in if you have more info than me?

I would like more input from you on this one if you can help him as I am trying to do on here. Not every mechanic knows everything. We are always learning new things every day. Let's look at this in a positive light and help this chap.

[Easy Rollins 1]

Ok do tell then...HOW?


I was an Australian Army heavy vehicle mechanic



Hey what intake number...I know a couple.

[rastus2571]

Had enough Easy,sorry to say .Deezzel whatever can figure it out from now.I am out of here on this post.

It's in his hands now.

Let him figure it out.

Seems I'm wrong when I post.

Worked on Cummins.Detroit,MAN,Hino. Lets help the poor guy out and get it fixed.

[Deezelweazel]

Hey, hey hey calm down a bit everybody- no offense included in this thread!
MAN, MTU, KHD's, Deutz and MWM do have also split heads- but a different engine design and waaaaay lower rpm's!

This engine runs on very low amounts of lubricating oil in the head. in fact this engine is the first one I know You can run with the head valve cover off without looking like a oil saturated salad.

So oil viscosity plays an important role. Too thin oil is relevant for engine trouble.
Also as already mentioned overreving plays a big part in.
Count in the warm up. In fact most (already) bent push rods jump out during warm up. To much force bending the rods and they pop out as fast as you can think.
Roll every push rod over a glass plate. If you recognize wobble change them out in time.

[rastus2571]

All yours now mate. Any diesel problem threads I have seen or posted
told them to contact you.

[Deezelweazel]

So- what is this answer good for?

Repeating the answers of the factory manual does not really help.

[xj25vm]

Hi all,

I know this thread has been dormant a good while (a year in fact). I am the OP - and it took me one year to find the time to sort this problem out :-)

I have checked yesterday the pushrod and it is straight. I have improvised a lever out of a long handle pliers for round clamps and managed to push the valve rocker up far enough to slide the push rod underneath it. I've reassembled everything back in place, refilled with coolant - and the engine started off first time - like it always use to do.

It all seems fine so far - I drove about 10 miles around town - I don't want to go any further in case it pops out again :-) We'll have to see how long it lasts.

Thanks again to all those who replied and helped along - and sorry for the long delay.

And as a side note - with the 2.5TD sold in UK - it is impossible to remove the engine head cover without disconnecting the three cooling pipes going over it - and loosing coolant in the process. I assume the instructions I've seen and claim this doesn't have to be done refer to the LHD version. Or that my engine has been heavily modified in some way - but it doesn't appear to be the case.

[The Smiths]

Glad its sorted - if it does happen again then weld a small nut to the arm to stop the rod coming out.

Also rocker cover does come off without disconecting the pipes - on about 20 I have done, so yours may well have been altered