My experience of removing a Top-Hat

[Mikexx]

An existing top-hat had suffered corrosion and wouldn't seal with the correct copper washer. So I decided to replace it. The saga started in the thread, "Changing injectors on a 1500"

 

I recall in this forum how easy they were to get out and how they might even come out with the injector.

 

So, I got an M8 tap and screwed this into the top-hat and there was minimal purchase, I had an M9 tap which I screwed in but couldn't really give it a good pull. M9 bolts aren't very common.

 

Next, an M10 tap, some studding and a nut and the thread pulled through the top-hat making a mess of the studding.

 

Next, an M12 tap, some studding and a nut and the thread pulled through the top-hat also making a mess of the studding.

 

Last ditch chance and no return using an M16 tap that in the top tat, where it made a thread from top to bottom inside the top-hat. Using a bolt and nut I wound the top-hat out. Sadly the brim was left behind.

 

So it's head off and swap for another. I expected its removal would be so much simpler!

 

[Tony Brooks]

Sorry to hear that. I have never known it to be as hard as that. I suspect it was a very long term leak so the top hat and head have corroded together.

[Mikexx]

I'm wondering if it's the original, so 35 years old. Thankfully I have a spare head that came from a seized engine.

 

When I've got time I can use a miller to cut the the brim out of the head.

 

I was initially feeling very pleased with myself as it seemed to come out smoothly! It was a good straight pull. I took the injector studs out and used a 5mm plate as per photo.

 

It's funny how experiences can vary, but I've not heard of this happening to anyone.

 

[Tracy D'arth]

If you have the head off you can knock out the precombustion swirl chamber and attack the heat shields from underneath. But do remember to remove the heater plugs first!

 

Sod's law, the good ones come out easy, the ones that have to be changed weld themselves in. 

[Mikexx]

 

Unfortunately I can't attack it from below. The central part has come through leaving a small annular rim that is inline with the head casting and leaving no ledge to knock it out with.

[Tracy D'arth]

I meant before you ripped the middle out!  I would take a sharp chisel to that remaining ring and chop it into two, slightly marking the head will not matter.

[BEngo]

Is it possible to get an end mill/ slot drill down the hole? You might need a long series mill or a drill that has been flat bottomed, and it will need to be a decent fit in the hole.  A battery drill at low speed or even a tap wrench will drive it. If you are lucky it will grab on the remaining 'brim' and loosen it.

Alternatively a good sharp  tap reseating tool of the right diameter should do it.

 

N

[Jen-in-Wellies]

An expert shows how it should be done.

[Mikexx]

On 07/08/2023 at 20:05, BEngo said:

Is it possible to get an end mill/ slot drill down the hole? You might need a long series mill or a drill that has been flat bottomed, and it will need to be a decent fit in the hole.  A battery drill at low speed or even a tap wrench will drive it. If you are lucky it will grab on the remaining 'brim' and loosen it.

Alternatively a good sharp  tap reseating tool of the right diameter should do it.

 

N

 

I have good access to a milling machine and a number of cutters. I have some step blocks so with shims I should be able to get the injector hole pretty much vertical. I only need to cut down to the copper washer so minimal risk to the head. I f I use a smaller cutter I should be able to cut just a side of the brim that should help loosen it's grip on the injector bore. My main  concern is how hard the material is. The fact I could easily tap a M16 hole suggests it should be ok.

On 07/08/2023 at 19:00, Tracy D'arth said:

I meant before you ripped the middle out!  I would take a sharp chisel to that remaining ring and chop it into two, slightly marking the head will not matter.

 

Yes, in hindsight that would have been an idea but TBH I was trying to avoid removing the head.

 

The fact I left the brim behind with a straight pull makes me wonder if sharp taps from below with the swirl chamber removed would have ended up the same result?

 

I have hit the top-hap from above with a metal screwdriver and I'm not convinced I'm doing very much. I'm also wary or hitting it any harder and breaking the head.

[Tracy D'arth]

I am fairly sure that you will find that the copper washer is not under the top hat but above it.

A sharp chisel and tapping with a light hammer will cut the ring remaining into 2 pieces without damaging the head.

[Tony Brooks]

8 minutes ago, Tracy D'arth said:

I am fairly sure that you will find that the copper washer is not under the top hat but above it.

A sharp chisel and tapping with a light hammer will cut the ring remaining into 2 pieces without damaging the head.

There should be one below it, it is different to the one under the injector. I suspect the OP's is missing

[Mikexx]

21 minutes ago, Tracy D'arth said:

I am fairly sure that you will find that the copper washer is not under the top hat but above it.

A sharp chisel and tapping with a light hammer will cut the ring remaining into 2 pieces without damaging the head.

 

I believe there are two. One which sites under the brim into the head, and another above holding off the injector.

 

Purchased from Calcutt:

BM12H218 INJECTOR HEAT SHIELD (TOPHAT) BMC 1.5 & 1.8

BM12H219  INJECTOR HEATSHIELD COPPER UNDER WASHER BMC 1.5 &1.8

 

The under washer is has a slight larger inner and outer diameter and thinner than the one sitting under the injector. I got 2 of everything due to my pessimistic/realistic nature.

[Mikexx]

One curious thing is when I took the head off the bores seemed to be sleeved, where the sleeve positions were different on 1, 4 and 2, 3. The pistons were marked std.

 

In trying to remove the injection pump gear drive oil strainer I destroyed it. I retrieved the remnants out of its bore and the bolt and confident nothing was left behind. The jet is clear. However I can't seem to find where to get one and most parts diagrams I have for this engine omit the feature and what it's called. I would like to replace this.

 

Finally, although the injectors were working and glow plugs glowing I had to put some oil into the cylinders down the injector bores to actually get it to start.

 

I am aware this engine after a previous head gasket change (not me) showed very poor compression afterwards, and this also needed oil in the cylinder to seal up the rings in order to get it to start.

 

[Tracy D'arth]

2 minutes ago, Mikexx said:

One curious thing is when I took the head off the bores seemed to be sleeved, where the sleeve positions were different on 1, 4 and 2, 3. The pistons were marked std.

 

In trying to remove the injection pump gear drive oil strainer I destroyed it. I retrieved the remnants out of its bore and the bolt and confident nothing was left behind. The jet is clear. However I can't seem to find where to get one and most parts diagrams I have for this engine omit the feature and what it's called. I would like to replace this.

 

Finally, although the injectors were working and glow plugs glowing I had to put some oil into the cylinders down the injector bores to actually get it to start.

 

I am aware this engine after a previous head gasket change (not me) showed very poor compression afterwards, and this also needed oil in the cylinder to seal up the rings in order to get it to start.

 

The bores are not equally spaced if this is what you mean.

I would not worry too much about the cam gear strainer providing you do regular oil changes. I have seen several engines that have run without and many where the filter has never been out for cleaning since new.

 

A lack of compression with new standard size pistons and rings in sleeved bores is very worrying.  I would check for rings that were broken on assembly and then measure what size the sleeves have been bored to.  Is the hone cross hatching still visible all down the bores?

A compression test would be instructive.

[Mikexx]

Thanks for the heads up about the strainer. It does get annual oil changes. It has solar panels so the engine isn't run every day.

 

It was more that the height of the liners that I noticed rather than spacing.

 

I don't recall any honing marks and all the bores seemed smooth. Once running it does sound pretty good with minimal oil consumption. The sleeves are not new and at least 10 years old. I also don't recall and tell-tale vertical score lines from a broken ring. The clearance around the piston seems about right and minimal lip on the bore. TBH I was taking more interest in swapping heads and getting the engine going due to lack of water on board and overdue a pump-out!

 

I should have a compression tester somewhere around here. I'm tempted to change the glow plugs as the plastic insulator on some have melted so an opportunity to kill 2 birds with one stone may avail in the near future.

 

Thanks for all the support.

[Tony Brooks]

But the 1.5 did not have liners, the cylinders were board direct into the bock, hence there could be no liner protrusion, unlike many linered diesels. So if you men the liner protrusion is different on all cylinders, that is not going to help head gasket longevity one little bit, especially between 2 & 3 where there is a very small distance between them.

 

The honing marks should be thousands of tiny scratches forming a diamond shape pattern. If the bores have a mirror finish then they could well be glazed, so pistons out and glaze-bust/hone. That could explain the low compression.

Edited August 10, 2023 by Tony Brooks