John Brown

Just noticed that the early blocks threaded for the single temp sender do not go all the way through into the water jacket. The threaded hole is blind.

Late blocks go all the way through and so the (longer) probe on the late sender is bathed in coolant.

Any one have thoughts on the reasons and merit of the two different designs?

M758

I don't believe they make any difference. I have used both early and late blocks in my 84 and never noticed any difference. I think they are calibrated to give the same signal at the sender wire.

FRporscheman

? My '85.1 had the temp sender going all the way through into the water jacket. A buddy's '83 we worked on was also like this.

John Brown

Think you're correct Joe. Standard VDO sending curve for both.

I was just wondering about any inertia in the readings. The early unit becomes almost a head/block temperature guage. Response to coolant temp changes are dependent on transfer through the aluminum - fast though that may be. On the other hand, assuming a 'normal' temp problem shows up first in the head the isolated sender might be slightly quicker?, not having to wait on the coolant to heat too.

Started out thinking the late style must be better. But I think I just convinced myself the early construction may have a slight edge in monitoring head temp. Or overtemp as the case may be.

One thing for certain my earlier concern that if you blew the coolant out the guage reading would suddenly become too low is probably wrong. Since it was never looking at actual coolant in the first place.

M758

That is how I noticed I had an coolant leak in my street 951. Coolant temp jump up and down faster than you imagine. Pulled over and found a pin hole leak in hose to heater valve.