old thornycroft 90 manifold trouble

[archie26]

The casting separating the internal galleries of my manifold is corroded at the exhaust end causing a significant water leak from the raw water coolant circuit straight into the top of the exhaust. Didn't seem to cause a problem whilst running, but I've had difficulty getting the engine to turn on the starter on occasions and I suspect coolant leaking back into the engine causing hydraulic lock.

Does this sound like a plausible hypothesis?

Has anybody come across a repair or re condition for this? Or know of a source of spares?

Asap stock a replacement but that is dissimilar, having an integrated header tank, whereas mine has a separate header tank at the alternator end.

Any suggestions gratefully received.

 

[archie26]

Picture attached

 

[rotrax]

You are going to have trouble repairing that.

If ASAP have a slightly different replacement I suspect modifying your boat to accept it would be the best way out.

Good Luck!

 

[Graham_Wright]

You could try "plastic metal". I can't remember the trade names but there exists a variety for different metals. Very effective.

 

[bristoljim]

The casting separating the internal galleries of my manifold is corroded at the exhaust end causing a significant water leak from the raw water coolant circuit straight into the top of the exhaust. Didn't seem to cause a problem whilst running, but I've had difficulty getting the engine to turn on the starter on occasions and I suspect coolant leaking back into the engine causing hydraulic lock.

Does this sound like a plausible hypothesis?

Has anybody come across a repair or re condition for this? Or know of a source of spares?

Asap stock a replacement but that is dissimilar, having an integrated header tank, whereas mine has a separate header tank at the alternator end.

Any suggestions gratefully received.

Can you confirm which engine you have - is it based on the 1.5 or the 2.2 / 2.5 - a photo of the engine will do.Graham was it Devcon you were thinking of ?
Jim

 

[footsoldier]

You could try "plastic metal". I can't remember the trade names but there exists a variety for different metals. Very effective.

J B Weld is often advised for this sort of job.

 

[Graham_Wright]

J B Weld is often advised for this sort of job.

That's the stuff.

 

[Aja]

'Chemical Metal' is very effective. I successfully repaired the manifold on my YSM12 many years ago.

Donald

 

[bristoljim]

Picture attached View attachment 86524

Ignore my post 5 - has the exhaust elbow got any jacketing or is it just a flat face which should form the end of the cooling jacket & seal between the exhaust & the water
Do you have access to any shot /sand blasting ?
Jim

 

[archie26]

It's based on the 1.5. The exhaust elbow has just a simple flat flange which seals off the end of the coolant jacket.

There appears to have been a previous repair with some sort of JB weld, but I think the source of the renewed problem is that deteriorating, or the corrosion spreading.

I took it to see a metal fabrications today and he phoned a friend who does aluminium welding. I'm going to see him tomorrow. In principle, it looks like a simple job to weld a piece of the right diameter pipe to the corroded stub, then cut it off flush with the rest of the flange mating face. (That's what he said, anyway).

I shall keep you posted.

 

[bristoljim]

It's based on the 1.5. The exhaust elbow has just a simple flat flange which seals off the end of the coolant jacket.

There appears to have been a previous repair with some sort of JB weld, but I think the source of the renewed problem is that deteriorating, or the corrosion spreading.

I took it to see a metal fabrications today and he phoned a friend who does aluminium welding. I'm going to see him tomorrow. In principle, it looks like a simple job to weld a piece of the right diameter pipe to the corroded stub, then cut it off flush with the rest of the flange mating face. (That's what he said, anyway).

I shall keep you posted.

You are on the right track as you appear to have lost too much material for using plastic metal - your welder would appreciate it being shot blasted so that he can see what is real metal to weld to & that may be too far inside to get at, he may need to cut the outer section away then weld back on aft the repair.
Jim

 

[archie26]

Thanks. I dropped it off this morning and he's going to have a go tomorrow or monday. At least he seemed optimistic. Wait any see....

 

[easton]

archie, I have two of those from my T90. It's a really early design before they used either the polar manifold or bowman BL180. You also have a separate tubestack/header tank where the thermostat housing would normally be.

For reference and if it's useful there is a company that makes new end-caps, I think they're based in Italy. I'll dig out the link as I can't seem to find it. The stub on the end cap always seems to corrode and deteriorate off so the hose is difficult to attach and seal.

I still have the two that I've removed, I'll check the condition and post pics if you're interested. They're heavy though, so even postage could be expensive.

From memory though at least one of them may have the same issue. A lot seem to develop this corrosion, presumably through age (they must all be 40 years plus old), alloy used and application (hot/warm salt water).

I replaced mine with a second hand polar manifold as the cost of the Bowman BL180 (fitted to both the 1800 (T108) and 1500 (T90)) is eye watering. Replacing it with either the polar or bowman is fine, just remove the header tank, replace the three studs with shorter ones and fit a new thermostat housing.

Andrew

 

[archie26]

Thank you. I've seen the price of the bowman replacements, my eyes are still watering.......

I should hear about plan A (the welding) tomorrow.

Plan B is a second hand replacement.

Plan C will be the Bowman route. I wasn't sure how it would fit on my engine, but your picture explains it all.

I'll let you know how the welder gets on. If it's a success, you might well have a couple of valuable spares on you hands once repaired, since there must be many more older T90s out there in similar condition.

Thanks again

 

[archie26]

As you might guess, the current restrictions are slowing progress on this. The welder has asked me for the internal diameter of the hole in the exhaust elbow, so he can get the size right on the manifold. Unfortunately, the marina is now shut and locked up as a result of the business closures enforced under the regulations which came into force last week, so I can't get to the boat to measure it and am well and truly stuck.

Does anybody have an exhaust elbow to hand? If so, could you do me the favour of measuring the diameter of the bore at the flange please?

 

[archie26]

Across here....

 

[easton]

Archie, that's the exhaust outlet end isn't it. Mine is pretty solidly bolted together but I'll see what I can do this weekend. (I'm not going anywhere )

why does he need to know that? He has the manifold.

Andrew

 

[archie26]

The mating surface of the manifold is so corroded it's difficult to get an accurate measurement. (Pics at top of thread) if he uses a piece of pipe too wide it might not make a good water/exhaust seal? Thanks for taking the trouble to respond and if you do have a look that would be great. Thanks.

 

[bristoljim]

The mating surface of the manifold is so corroded it's difficult to get an accurate measurement. (Pics at top of thread) if he uses a piece of pipe too wide it might not make a good water/exhaust seal? Thanks for taking the trouble to respond and if you do have a look that would be great. Thanks.

Is there a blanking plate on the other non corroded end of the manifold ? which if removed would give him the size
Jim

 

[archie26]

The other end is configured slightly differently. He could get the internal diameter of the exhaust gallery from the manifold, but from the remaining uncorroded portion of the exhaust end, this appears to flare out a little before the mating surface, hence my (and his) uncertainty over the final dimensions of the exhaust outlet where it mates with the flange.

It suddenly occurred to me that I could measure the exhaust aperture in the new gasket I have waiting for the reassembly job..... but, yes, you have guessed.... that too is on the boat, locked in the marina.

Perhaps somebody has a gasket set for one of these and they could measure the central hole diameter for me please?