Tap Tap Tap

[Kane 34]

Hello,

 

I've recently finished an mi16 conversion into the old 205 and although she runs well, only my opinion as I've never had a shot in another so can't make a comparison, I have a slight tap from the top end which I'm trying to resolve so am looking for some advice.

 

I rebuilt the engine after having everything sent off to have work done. Block was decked 4 thou. With the head receiving a slight skim as well. Standard oem quality head gasket was used when assembling.

 

What I have now is a good tap coming from the top end and wondered what all possible issues may cause this? I have had the belt cover off already to check the pulley bolts and both seem tight. I've also had the cam cover off to see if there was any apparent issues or loose bolts I could see but no luck there.

 

I'm currently still on the 2nd dose of running in mineral oil (first changed after 25 miles) but have ordered 6litres of Fuchs something or other fully synth 5w40 which will be here next week. I'm hoping that will calm things down but I'm trying to plan ahead in case otherwise.

 

I refurbed the lifters when the head was in bits according to PeterT's description on his website so was hoping these would not be a problem but I guess they could be. Is there any definitive way to check to see if the lifters are sticking without disassembling the head?

 

My biggest worry is that I've got slight valve/piston clashing which is causing the tap, is this a likely candidate? What would be the best way, if any, to check that there hasn't been valve/piston contact? I'm guessing a compression test would show up something if there were bent valves? Maybe time to go buy a decent tester.

 

Apart from the points listed what other issues have people found to be the cause of this problem?

 

Thanks in advance

 

Kane

[Kane 34]

Here's a quick video

 

http://s1288.photobucket.com/user/KHarrison31905/media/20141117_184954_zpsuypm2a73.mp4.html

[welshpug 1,657]

hard to tell from the video, but has it had a decent good RPM run? as it sometimes takes a while to fill up tappets that were completely empty.

 

as for a compression test that often doesn't highlight a bent valve if its slight, strong valve springs tend to pull them enough to seal, that constant bending and straightening is what makes them fail eventually.

 

however the MI does have particularly generous valve cutouts so contact isn't a great concern.

[Kane 34]

I followed the generic 'hard' run in procedure initially so short stabs up to 4500rpm for the first hundred miles or so then gradually increase. Unfortunately my rev counter has started sticking so stops around the 4k Mark. I've pushed it a bit now and then but not hit the limiter yet.

 

Ah ok I see, that's a little comforting about the amount of space these engines have. I take it the only real way to determine a bent valve is to take them out the head and have them tested?

 

Have you got any other suggestions on what I should check over next Mei? I'm hoping the oil change will do the trick and will report back my findings probably the middle of next week when I get the delivery.

[Kane 34]

Took the motor further up the rev range on the way back up the road last night, still didn't hit the limiter but must not have been to far away. Checked it when I got back and unfortunately no change so I don't think it is that the buckets aren't filling up properly.

 

If it turns out to the the lifters themselves being worn what is the best course of action to rectify the situation? I know I've read on here that aftermarket sets are mostly crap so to steer clear. Is it worth while trying to get a decent used set or are there any other cars which use a similar setup which are more likely to be in a better condition?

[unariciflocos 49 1 Cars]

I know it's not what you want to hear, but it's more likely a bent valve than worn lifters. I've had the same issue and they found 2 bent valves. I think XU10J4RS are a direct replacement.

[Kane 34]

Was it a clearance issue that caused your bent valves or a timing problem? The thing is my head was stripped by me but sent to Gardias engine services for overhaul ( clean, 3 angle seats, inserts and valves checked etc etc) and rebuilt by them with appropriate shims.

 

I rebuilt the engine checking that all the timing holes aligned several times and every time checked out. I didn't do a piston/valve clearance check at the time and in hindsight probably should have. The thing is I don't remember the noise being so pronounced at the very beginning of having the car started, maybe I just wasn't listening for it.

 

I'm sure I've got a picture of the head prior too assembly I'll try pull out and post up. From what I've read the mi's can take a hefty skim which I don't think my one has so that should give some leeway.

[Kane 34]

Here's a photo of the head here. Looks pretty tight on the inlets right enough..

 

[welshpug 1,657]

shims?! have you had it converted to solids?

 

j4rs valves will not fit, stems are smaller diameter and different diameter head

[Kane 34]

Sorry talking absolute nonsense there, ignore that comment! No coffee on a Monday morning obviously taking its toll

[petert 586]

Is it possible you re-assembled the pistons in the lifters upside down? It's a common mistake. It definitely has an issue which can only be resolved by disassembly and inspection.

[Kane 34]

I don't think so Peter as I followed the instructions pretty closely but to be honest can't remember exactly as it was a good year ago that I did the work. I'll have a look through my photos and see if I have any evidence of me doing that part.

 

I'll see how The oil change affects things and then will look to removing the cams to inspect the lifters if that doesn't prevail. I really hope I will not need to remove the head!

[unariciflocos 49 1 Cars]

In my case I think it was improper handling of the head just before or during fitting that caused the bent valves. I was refering to j4rs lifters, but after re-reading my comment now I see how I wasn't specific enough.

 

Don't know if you can shift the lifters around and check with a stethoscope whether the tapping moves as well. This would indicate if it's a lifter or a valve.

[Kane 34]

Could someone confirm with me which way round each component in the picture should be assembled. Im sure I did install them correctly but just want to confirm

 

[unariciflocos 49 1 Cars]

Spring over the small nipple, then inserted spring first into the piston on the left IIRC. You can actually see in the center of the piston where it pushes the stem of the valve.

[Kane 34]

Pretty positive that is how I had them built up. I'll need to confirm if I end up taking it apart again.

 

If I was to remove the cam cover would it be ok to turn the car over to see if I can listen out for the tap? Obviously leaving off the leads so it doesn't kick into life.

[unariciflocos 49 1 Cars]

I did it, but you'll have oil dripping over the exhaust side because of the tilt of the engine and don't think you'd be able to hear the tap anyway at cranking speed.

 

Just get an engine stethoscope from ebay for 5 quid and you can find it with the cover on.

[Kane 34]

In terms of checking for lifter problems with the stethoscope would you just put the probe on top of the cam cover roughly above each lifter and see if there is a change in noise between them?

 

Also where would you locate the probe to check piston/valve contact?

[unariciflocos 49 1 Cars]

Just run the stethoscope along the rocker cover until you find the loudest spot.

 

I was abe to identify a loose piston pin by putting the stethoscope on the front of the block just under the head, maybe it would also work for listening for potential piston valve contact?

[Kane 34]

Cool I'll get one ordered up once I have changed the oil. Thanks for the advice

[Kane 34]

Been out and changed the oil for Fuchs super synth and a new filter of course. Haven't had a chance to take it out for a run to allow the buckets to properly fill but thought I'd have a listen to the head and see what I could hear.

 

From listening to the engine the tap sounds a lot louder on the cambelt end than at the flywheel so would that point to a dodgy lifter or could it still be valve related?

 

I'm going to buy one of those stethoscopes that was recommended to see if I can pinpoint the source of the problem.

[petert 586]

You're only delaying the inevitable. Start pulling it apart. Check the lifters first. If they check out ok, then it has to be a bent valve. Mi16 valves don't normally flex back like GTI6 valves however, due to their larger stem. If bent, they'll stay bent and you'll have poor compression.

[Kane 34]

How do I actually check if the lifters are at fault? I'll go get myself a decent compression tester first and see if I can see signs of a bent valve. Seems easier checking compression First

[welshpug 1,657]

give them a prod with something hard plastic, if faulty they'll move easily.

[Kane 34]

Ah cool I'll give that a go once I've checked the compression. Just ordered a gunson tester so that should be here in the next couple of days.

 

Just out of interest what is it that usually causes the lifters to fail? Collapsed spring?