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Water pump Plug?

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Mountain_man

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Ok I've tried to find info for setting up my sending unit. I'm thinking of using the plug on the water pump. Anyone know what threads and size it is? Suggest a better location? I would normally use a standard spot however it's a 91 suburban and the intake location is taken as is the spot on drivers side head.

If perhaps I put the thermostatic switch on the drivers head location where can I place the temp gauge sending unit? Or even can I place that gauge wire on the sender on top of the intake. I've searched for this info and only seen anything about older units with one of the two locations open. Any advice or post pointing I would appreciate, this is driving me crazy!
 
Any reason you can't use the one on the passenger side head? Same casting as the other side, so it's towards the back. :)
 
Depends on the year of the heads, they had two different sizes. Can't recall which is which, I *think* later is smaller diameter than earlier, but 3/8 is probably right for one of the two. :)
 
If you place your sending unit on the head the temperature reading will always be around 220 - 250F. The temp is probably accurate ( normal head temp ) but makes me uneasy. If you can use the water pump plug, it will read 180- 190F.
They (Jegs) make a thermostat extention ( 2 inch ? riser ) with a fitting on the side for a sending unit. The cost may be steep, but the reading would be indicative of true engine temperature.
 
Why wouldn't the cylinder head be a correct reading? They should read at whatever your thermostat rating is.

I've never had a GM vehicle with the sender in the correct location (drivers side head), including my current truck(s) that read anything other than actual thermostat temp, except when something was wrong.

Water pump would be a false reading, as that is outside of the engine, and only indicates the temp of the coolant leaving the radiator. The water pump moves "cold" coolant on typical small blocks. If the thermostat failed closed, or something similar happened, and coolant wasn't leaving the engine block, temperature would spike in the engine sooner than you'd see it on a temp gauge with a sender in the water pump, and that would be disastrous.
 
i personally think that, the head temperature is what you'd really want to be concerned with anyways, if those are getting too hot, there's bound to be a problem soon.

I have always hooked up aftermarket water temp gauges in those ports, and always received decent readings from them.
 
I concur...

ummm, it's where the factory puts it... Why would you see temps upward of 250?

There are alternatives, but that is the best, if ya can get the damn thing out...
 
Seems everyone has jumped to conclusions that you're talking about a temp sending unit for your temp gauge. Regardless even if you're talking about a sending unit for electric fans it needs to come either from the heads or the intake manifold. As someone else already said the water pump is reading the cool temp of the water leaving the radiator and is not of any use for either a temp gauge or an electric fan sender. The sender hole in the heads if they are early heads is 1/2" NPT and if they are the later heads then it is 3/8" NPT.
 
Water is pumped from the radiator into the engine and then goes back to the radiator throw the upper radiator hose.
 
I put my temp switch for my electric fans in the tapped hole in the water pump and it seems to be working fine so far.
Tarey
 
GNERGY said:
I put my temp switch for my electric fans in the tapped hole in the water pump and it seems to be working fine so far.
Tarey
Click to expand...

What size hole did you have? Thread size I mean. Do you have any idea how accurate that reading is? Just hoping it's close as that's nice and easy location. Thanks.

Also what thermostat and switch did you put in?
 
I don't remember if the hole is 1/2in or 3/4in I can look tomorrow.
I used a 185* temp switch and a 180* thermostat.
Tarey
 
ok another question. The plug on passanger side of head is not coming out as it should. What size square piece is it to take out? It's slightly smaller then the ratchet size (3/8) and it is a square. Do they make such a tool? Where can I fnd it. This is driving me nuts!
 
I'd wait until someone can definitively say, but I'd be surprised if it was anything other than what a 3/8" ratchet will fit. It's what they used for the diff fill as well.
 
It's if anything only 1 size smaller or a metric size plug. I'm hoping someone can get me this info or somewhere else to put this damn sensor. Perhaps waterpump plug is my only other option
 
That plus is a 3/8" square drive plug. It is doubtful that you'll get it out without drilling it. Depending on the year of the heads it's either 3/8 " NPT or 1/2" NPT threads.
 
none of my 3/8" will fit in that hole. The one on waterpump is 3/8 however and fits perfect. The head side one appears to be smaller as the plug itself doesn't even come close. Any fan switches that double as a temp sender? lol driving me nuts
 
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