How important is the alternator heat sheild on a 300TDi?

**mox** · 16th February 2013, 09:39 PM

Have only had by Marelli 65amp on '97 build Defender 130 apart once. Was after I saw somewhere that rear needle roller needs regreasing regularly because it has no seal. Anyway cleaned mine and put some nulon red grease in, which seems to tolerate high temperatures. Also, found an appropriate size O ring in my box of them to put over the shaft and act as a seal. Of course like assembling many things with new O rings incorporated, they have to be checked for size, sometimes with trial assembly.

Alternators can overheat - and if excessive cook themselves due to combination of radiated heat, hot ambient air and from producing heat somewhat in proportion to the charging rate. Looking at this alternator, which I gather is a design from Joseph Lucas, appeared to me it had far less holes in the body to allow entry of air, pulled by the alternator fan on the pulley end than the common Australian made Bosch. So while it was apart, drilled several extra holes in rear casing - where they are not obstructed by something that will stop air flow. Presumably mine will now run cooler than a standard alternator in the same conditions and load. I think it is a good idea to keep the heat shield on. Have also made one for a previous vehicle I nowned.

2stroke · 17th February 2013, 06:44 AM

I changed my alt to a Bosch years ago and changed the heat sheild over on to that as well.

**86mud** · 23rd February 2013, 10:18 PM

Well...favricated my own heat shield. I used the bolt that holds the dipstick to the block as the mount for the bracket. I did use some heat proof material as well, but that might be overkill.

Cheers

**Judo** · 24th February 2013, 12:23 AM

Mine broke off a while ago and I haven't done anything about it. I'll let you know if it goes up in flames anytime in the future.

**rick130** · 24th February 2013, 08:59 AM

Originally Posted by Judo

Mine broke off a while ago and I haven't done anything about it. I'll let you know if it goes up in flames anytime in the future.

Naa, I doubt that'll happen, they just cook the back bearing in low speed off road stuff.
I'm guessing there's enough airflow through the engine bay in day to day driving to reduce the problem.

**Bushie** · 24th February 2013, 09:02 AM

Originally Posted by 2stroke

I changed my alt to a Bosch years ago and changed the heat sheild over on to that as well.

Which bosch unit did you use ? - instructions/pictures ?

Martyn

**Judo** · 24th February 2013, 10:23 AM

Originally Posted by rick130

Naa, I doubt that'll happen, they just cook the back bearing in low speed off road stuff.
I'm guessing there's enough airflow through the engine bay in day to day driving to reduce the problem.

Slight hi jack maybe sorry, but on the point of no air flow making the engine by hotter - I've been watching my new VDO temp gauge and noticed yesterday after driving on a hot day the water temp was at 90 when I stopped and immediately turned the engine off. Came back 10 mins later and it was at 100. It would never do that if I left it idle (water pump on). I thought it was interesting how much it rose without any air or water flow even with engine off.

**PAT303** · 24th February 2013, 11:17 AM

My original Marelli cooked the rear bearing in Tasmania over a decade ago and I replaced it with a Bosch 100A out of a Ford Transit without the heat shield,never had an issue since. Pat

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