Bypass Hose Removal

Post by **Kevin** » Thu Oct 16, 2003 10:46 am

I was just wondering if the bypass hose can be done away with.
On some 1275 heads I know the bypass hole is not drilled through, and if you use this type of head it requires a metro water pump to do away with the outlet (or blank the exisiting one off) I have also seen heads that appear to have a blanking screw in the outlet which would mean that you could use either option.
Does anyone know if the same applies to the 1098 engine, because if a screw fitting blanking plug is available that would enable the Bypass hose to be done away with.
Would this cause any problems, has anyone tried it.
I just thought that if originality was not an issue the removal of a pain in the neck issue might be a good thing.

Post by **Cam** » Thu Oct 16, 2003 11:05 am

I don't have a bypass hose on my 1380 as it uses a modified Metro head. I think that the 998 Metro head also has the same setup.

You can either use the Metro thermostat housing and do the plumbing the same as the Metro (extra connection under the thermostat) OR the simpler way is to change the heater tap connection to a straight one (Ital type) and have the heater matrix circulating coolant all the time.

If you go for the original Metro set-up then the top hose connection will not line up with the radiator as it will be too far up from the head. Not a problem if you use the Metro radiator - but that's extra work!

To be honest, if you can get a bypass hose system then go with it. It's much easier!

Post by **ianselva** » Thu Oct 16, 2003 4:33 pm

I'm not convinced you need one at all . Can someone suggest what it might be used for . Even when the thermostat is closed there is a small hole built into it. I haven't used one for a long time , especially as the heater valves never seem to close 100%.

Post by **rayofleamington** » Thu Oct 16, 2003 6:15 pm

the small hole in the thermostat is mainly a filling aid. It doesn't give a lot of flow so I wouldn't want to run without a bypass hose.
As cam said you can remove the heater control valve (saves the leaks and headaches..) so that there is still some flow with a closed thermostat.
Removing it completely will lead to an engine meltdown if/when the thermostat fails shut. With a shut thermostat, the bypass hose allows some circulation and you can limp home at about 50mph.

Post by **Willie** » Thu Oct 16, 2003 7:47 pm

Here Here, I have experienced a Thermostat failing in the
shut position,on a Triumph Herald and it was quite alarming,
the engine was threatening to jump out of the car!!