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RE: [T3] Number 4 issues..


On 4 Jun 2006 at 11:03, Dave Sanderson wrote:

> We got our blown engine apart and it was a mess. However, it was the  
> number 1 rod that let go not the # 4 that everyone else seems to have  
> experienced. We're thinking that the engine must have overheated  
> because those little flaps on the back of the cooling fan did not  
> open. We're not 100% sure about that but have no other explanation  
> unless the parts I used to build the engine were not as good as I  
> thought. The case appeared to be fine and the machine shop said that  
> they didn't think it needed boring. The crank had been reground 0.020  
> with all new bearings etc. So, my best guess is the engine simply got  
> too hot. We're now thinking, when we build the next engine, that we  
> will remove those flaps completely. We live in the Pacific Northwest,  
> Vancouver B.C., where it never gets that cold and so we probably  
> don't need those flaps. Maybe the engine will simply run a bit cooler  
> all the time. Does that make sense to you?

I try to use cranks that have been reground no more than .010, but I 
built one engine with a .030 crank and that one survived for at least 
a year. (It went in the case that I had annealed.) Berg can weld 
counterweights onto a std/std crank and then straighten it if 
necessary. This gives you the strongest crank with the hardest 
journals.

Don't remove the thermostat, etc. While lots of people do this, it's 
never done by those who really understand what they're doing. The 
thermostat is essential for getting the engine thru its warmup period 
quickly, otherwise it spends a lot of time warming up and this causes 
excessive wear.

As others have stated. You should install all the cooling parts, and 
MAKE SURE they are working properly. 

It's important that you not try to guess about what caused your 
failure. Take a good look at your damaged parts and try to deduce the 
cause from the evidence in front of you. It's not likely that 
overheating would cause a rod bearing failure, but I would look for 
evidence that dirt from the oil galleys got into that bearing and 
either stopped the flow of oil or abraded the bearing. It's very 
important to clean the oil galleys carefully when you rebuild an 
engine. On engines that have had a failure like this it may be 
prudent to either discard the oil cooler or to clean it out VERY 
thoroughly. You don't want metal bits from your last failure to cause 
your next one.  ;-p

-- 
*******************************
Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
*******************************

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