What is the small coolant hose that is under thermostat going to top of block? And can I plug it off.  I think the little pipe is rusting off. It is on a trike, definately not to be driven in cold weather.

Edited October 17, 20205 yr by montermahan

39 minutes ago, montermahan said:

What is the small coolant hose that is under thermostat going to intake manifold? And can I plug it off.  It is on a trike, definately not to be driven in cold weather.

The one that goes to the hard line? That's for the intake heater.

After closer examination, the line goes from thremostat housing to the top of the block.  Sorry.

 

I’ve disconnected and not run the throttle body heater hoses with no issues.  That was in MD with plenty of subzero temps.  If it’s used in freezing temps it’s not ideal to remove it though and I wouldn’t do it again that far north. And this is assuming the last poster is correct that this tstat hose is for the TB hoses. 
 

I have the theory that this hose is sometimes important for air pocket escape. I have done a repair to block by taper tapping to 27? TPI  in 1/8" to accept a 45° brass elbow male into block then female to take a barb fitting.

This neatly clears the MPFi twin port turbo intake.

Another I have bypassed the TB due to rotted fittings - no freezing up. Another I didn't do the bypass, I totally taper tapped and plugged the holes, right and left of manifold

Edited October 17, 20205 yr by Step-a-toe

I see what you mean about airlock.  I put a peacock on top pf thermostat housing and force coolant in there with motor running to get the air out of that area,  but I guess I better do as you suggested with a tap and hosebarb fitting, don't know how much air could be trapped at top of block and what harm it could,do.

Peacock eh? Only works while you have it open . Good idea for filling, but no benefit while running

Trapped air won’t cool. And it can allow the cooling system to push fluid out the rad overflow as air will expand more than the coolant. 

No overflow reservoir will see your radiator lose coolant over time until it reaches a certain level where it can’t push any more fluid out. 

By all means, block off the throttle body warming circuit but I’d be keeping the block to thermostat housing hose.

Cheers 

Bennie

I did build the overflow reservoir and will continue using the small hose.  Thanks for reply

Air pockets don't allow heat transfer so bits get hotter!!

If you don't get around to a good repair , that hose is a handy to nobody 5.5mm ID