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

[86mud]

Hi all

Finally am just finishing off putting my 130 back together after the dramas of a sheered alternator bolt (lower).

After 3 weeks I was finally able to drive it today. What a drama. Had to helicoil the bottom mount, and to do that I have to remove radiator and condensor, order new 100 amp alternator, and new water pump as it had a hairline crack near the lower most bolt hole.

Attached is a pic of the alternator...in pieces! It was installed on in August 2010.

The issue is the new alternator. I am unable to mount the original heat sheild to it. There is nothing to bolt onto at the back of the alternator. The previous alternator had extended bolts out the rear of the alternator, but the new one has a smaller sized thread so I can not use the extenders.

Is it cricial to have the heat sheild there? It does concern me being so close to the turbo.

Thanks

[jboot51]

Mine has been missing for 10 years now, with no ill effect.

[rick130]

It was really common in the early days of Tdi's to cook the rear bearing of the alternator in low speed/high load off road stuff.

The Disco 100amp ones use a Bakerlite type heat shield, the aluminium one won't fit.

[mike_ie]

The older 100A alternators had the headshield out on three extended studs, the newer ones don't have them at all. I actually enquired about this at TRS when I was replacing my alternator a few months back, and they said that it's not a problem.

[86mud]

Hi Rick

Is that something I can buy as a part

Cheers

[rick130]

Andrew, I don't know, all I know is that I bought a 100amp alt. a few months back and it came with the Bakerlite heat shield.

The old 65amp ones would stuff the rear bearing as it's such a small needle roller and not sealed.
I used a non-melt high temp, race car bearing grease and it lasted for years, but I also repaired the old heat shield when it cracked and kept it in place.

Have to say I haven't heard of too many carking form the dreaded rear bearing failing for a few years now, but maybe everyone's replaced them with Disco ones by now ? (which have a nice big roller bearing in the back)
I'd want the heat shield just to protect the regulator moreso than the bearings too.

[mike_ie]

The old 65amp ones would stuff the rear bearing as it's such a small needle roller and not sealed. too.

If I'm not mistaken, the standard 65A Lucas that came with the Defender 300tdi didn't have a rear bearing at all, but rather a phosphor bronze bush instead, which is where the problems used to lie. The 100A Disco Marrelli unit has bearings front and rear, and are a hell of a lot more robust.....

[rick130]

Naa, it's a tiny little INA needle roller Mike.
The inner sleeve is pressed onto the alt shaft and is the same OD as the shaft.
I've had it apart a few times to regrease.

[86mud]

Looks like I will jhave to fabricate something....might be able to make a bracket using the bolt that holds the dipstick to the block....and use some flat steel say 25 x 3 coming out behind the alternator then affix a piece of aluminium flat sheet to that....

Cheers

[mike_ie]

Naa, it's a tiny little INA needle roller Mike.
The inner sleeve is pressed onto the alt shaft and is the same OD as the shaft.
I've had it apart a few times to regrease.

I stand corrected :)

[mox]

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]

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

[86mud]

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]

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]

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]

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]

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]

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