help fitting spark plug head temp sensor--no room?

[GusC2it]

I bought a VDO head temp gauge for my 2.0L '75, there is no way I can fit the sensor under the spark plug, no mater how careful I bend it!! Help! The counter bore around the spark plug hole is just too small.
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75 type 2 http://gusc1.tripod.com/1975vwtype2
Old vices have now been upgraded to bad habits.
http://www.facebook.com/pages/VW-Wild-Weekend-2011-St-Pete-Fl/197064760336111

[Patrick199]

Germansupplyscott did a good write-up on installing these stupid things. I think it can be found on his website and here on the samba.
If memory serves, I think I had to make the hole a little bigger so the spark plug would fit through it. This also helps to keep it from binding when you thread the plug back into the head.
You can bend the sender with two pairs of pliers or a vice and whatever else you want to use.
When you go to thread the spark plug into the head, pull up on the sender's wire so it stays at the top of the plug's threads, where the washer was - I think most people cut the washer off the plug. If it's just sitting on the head when you thread the plug back in, it can catch a thread and actually get screwed into the head with the plug. The plug will not go in all the way but you might not realize it because it's so hard to see down there. You'll be left with a bad seal between the plug and the head, the sender won't work properly because it's all munged up in the hole, and the threads in the head are likely to get screwed up in the process also.
Sometimes I wonder if it's even worth having the gauge. I always dread pulling that plug out because it's such a pain to put back in.

[CarlSpackler]

It'll fit, it's just tight. I just put a VDO sender on a new 2.0l. Make sure you bend it so the criped connection to the wires faces the plug, otherwise you risk getting that crimp caught on the head when you put the plug in and making a tear drop out of the ring. Then it won't seal correctly.
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'67 Micro Bus
'73 Thing
'91 Westy

[1FUNBUG]

You better stop cross posting the same question or the admins will slap your peepee.

I assume the engine is still in the bus. I think you're going to have to notch out the cylinder head to provide a channel for the tail of the ring terminal to sit in. Is that the problem or is the O.D. of the ring terminal to big to actually fit in the hole? Check out the tech article at www.germansupply.com

Also "use the search function" and find the thread in this forum that is titled "CHT Nirvana"

Report back
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1FUNBUG

71 Beetle, 1776, dual Kadrons
77 Westy, Camper Special 2.0 F.I.

[GusC2it]

Thanks guys !! The plug fits thru the sender OK, but the crimp is too thick. Making a notch or grove for it is the only way i can see it working, but I hate to do that. Looks like a NGK plug will help also. That link has a lot of good info...Sorry about the double post.
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75 type 2 http://gusc1.tripod.com/1975vwtype2
Old vices have now been upgraded to bad habits.
http://www.facebook.com/pages/VW-Wild-Weekend-2011-St-Pete-Fl/197064760336111

[nikita]

Think of trying this sender instead.

http://www.sonexaircraft.com/eshop/cart.php?target=product&product_id=16597&category_id=336

[GusC2it]

[Jody '71]

So, with this type of sender, where on the head are you supposed to install it with the self tapping screw to get the best CHT reading?
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'66 Beetle
2011 Hyundai Elantra Touring

[1FUNBUG]

[GusC2it]

Would that be ambient temp inside the car, at the gauge? If so, it still makes a difference where you mount the probe. I think the next hotest mounting point would be a head nut. I believe the VDO is calibrated for 75 F ambient at the gauge. so it its 90 deg under your dashboard, you would add 15 deg to the gauge reading. Right?
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75 type 2 http://gusc1.tripod.com/1975vwtype2
Old vices have now been upgraded to bad habits.
http://www.facebook.com/pages/VW-Wild-Weekend-2011-St-Pete-Fl/197064760336111

[grandfatherjim]

It's ambient at the end of the thermocouple, and in your example you would subtract 15 degrees, not add.
In the case of the Westach, I think it's 4' long so it could be in the passenger compartment, albeit at the back.
If you keep your passenger compartment at room temperature, the reading will be fairly close.
Jim

[Jody '71]

But my question still remains, where is this sender mounted to the head with a self tapping sheet metal screw? I am currently using a DD CHT set-up with the ring under the plug. It functions flawlessly, but that's because the ring fits the plug as should be, and it is not ovaled out. Anything other than that will result in questionable readings and higher head temps. Does this sender wire loom come in lengths suitable for Bus applications? Is it functional with a DD CHT gauge?
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'66 Beetle
2011 Hyundai Elantra Touring

[busdaddy]

I just modified a VDO sender with a new smaller ring and screwed it to the head beside the spark plug hole last month (shoulda took pics), engines still out of the bus so no comparisons yet but it's definitely going to eliminate the plug washer hassle.
I drilled and tapped a shallow hole on the vertical area just below/beside the plug, it's 3/8" away from the plug so I doubt temps are going to be much different.
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[CatfishCalhoun]

Jody,

Here's the picture from the link above:

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". . . In beer there is freedom,
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[GusC2it]

I just attached mine on an exhaust stud using a washer between the probe and the nut. It looks good. I wonder if that area is hotter or cooler then at the plug? Anybody see any problems with this??
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75 type 2 http://gusc1.tripod.com/1975vwtype2
Old vices have now been upgraded to bad habits.
http://www.facebook.com/pages/VW-Wild-Weekend-2011-St-Pete-Fl/197064760336111

[Randy in Maine]

Not good enough to tell you what you want to know (the cylinder head temperature).

You need it under the plug to give you good information.

[GusC2it]

Randy, Not good enough in what way??
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75 type 2 http://gusc1.tripod.com/1975vwtype2
Old vices have now been upgraded to bad habits.
http://www.facebook.com/pages/VW-Wild-Weekend-2011-St-Pete-Fl/197064760336111

[Randy in Maine]

Well you are looking to keep your CHTs from going to the meltdown point of about 400º when the gauge sending unit is properly installed.

When I got my bus it had a CHT installed at the TSII location and it was not even close to what it was under the #3 plug.

It is up to you, your bus your money. If it were me, I would intall it where it is supposed to be or not even put it on.

Just my 2 cents though.

[jl74supercab]

It seems to me that locating the sensor on the #3 plug is ideal in reference to the 400 degree melting point; however, what is really important is the delta of heat increase. In other words, if the difference between the normal reading at the #3 cylinder and the danger point is 50 degrees F, then you can assume that if you locate the sensor in a different location, you should get worried when the CHT climbs in a relative manner. If you get 275 at the TempII location and it climbs to 325, then you have a problem. The increase in temperature is what is important, not the absolute number. You would also want to take into account that the temps may not rise in the same proportion, but a drastic increase will alert you to a problem. Certainly better than no CHT at all.
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73 Riviera Camper - "Julius"
74 Super Convertible - "Someday"

[dweller]

how much, if any, temp differential would be caused by the heat from the sparkplug firing itself?

i would guess the plugs generate some heat on their own?

dp
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77 Westie 2.0L FI ... slowly restoring bit by bit...