summertime coolant temps?

[atl gn]

My scanmaster reads the coolant degrees as 170-180 with a 160 stat, but my vdo gauge always reads 10-15 degrees hotter. I have heard that vdo gauges lie about 20 degrees in the summer, but is the reading from the scanmaster an accurate reading? I believe that the scanmaster reads from the intake manifold, and I know that the sending unit for the vdo gauge is below the header but should these temps still be that far apart?

I guess the real question is which reading should I go by....Thanks

 

[turbo buicks]

if you stuck the VDO in an oven and looked at the scanmaster which would you go by. the scanmaster of course. the VDO is an independent gauge setup and runs on its own. what the computer sees and what the VDO sees are 2 different things. what does the computer use to adjust different parameters and settings while driving? it uses what it sees which is what the scanmaster shows you. i would use the guage to get a general idea of the coolant temp. but for tuning and and all that good stuff i would use the scanmaster, IMHO

HTH

 

[atl gn]

thanks turbo buicks, I see you are from Florida- so you drive in about the same temperatures than me. What temps do you run in the summertime on a hot day. Thanks

 

[BoostMasterK]

Confucious Say...

..."Man with more than one watch, never knows what time it is"

In short, I'd believe the ECM/scan tool.

I have the same problem as you, my electric temp gauge reads about 15 degrees higher than the actual ECM temp. But I believe the ECM temp because of the thermostat.

With my 160 degree thermo, I start the car, the temp will gradually rise above 160, then quickly dive back down below 160, then settle down to about 162 and stay there. Try that and see what they both say.

Mike [

 

[FlyinGN]

My VDO generally reads about 5-7 degrees higher then my scanmaster. I guess im lucky I believe the scanmaster..

 

[Steve Wood]

The scanmaster is reading an electrical sending unit. Electrical senders are often not as linear as a mechanical unit.

The VDO gauge could be either electrical or mechanical. If mechanical, it could be more accurate but quality could come into play.

As they are in different locations, who knows?

I normally find the factor unit reads about 5 degs higher up in that range than does my mechanical gauges whcih are mounted in the warning light hole on the intake. I believe my mechanical gauges more than the SM.

 

[BoostMasterK]

Originally posted by Steve Wood
The scanmaster is reading an electrical sending unit. Electrical senders are often not as linear as a mechanical unit....quality could come into play.

I agree, mechanical is generally better but the quality is a big factor. Steve, how do you feel about the accuracy of the thermostat? What does you car run at right after the thermostat stabilizes?

Mike [

 

[Steve Wood]

Right after it stabilizes, mine runs about 163.

It runs hotter than that as the engine runs, tho. I just drove my GN to the farm to leave it this week end. It was not a very hot day due to the heavy rains we had been having. It sat on 167-168 according to the SM....bout the same on the Autometer mechanical gauge. At 70 mph, on a 100 deg day, I usually run 168-170. It ran about 5 degs cooler before I started running my tranny cooler back thru the radiator as well as the external cooler.

Driving my T the other day on a hot day...I noticed both units read 170 at the same time but after I sat in traffic awhile, the gauge read 185 and the SM was 192.....when I would drive the temps dropped and were closer together.

I would not necessarily say the Autometer is a quality gauge but mine do seem consistent.

 

[BoostMasterK]

Originally posted by Steve Wood
Right after it stabilizes, mine runs about 163.
It runs hotter than that as the engine runs, tho

That's fine, I think that supports my feeling about the thermo being a pretty accurate measure before the car gets all hot and bothered.

As for in traffic, the mechanical might be more linear than the electric or maybe there's a difference in location. I guess ou could prove that out by swapping the locations, but I don't think it's worth the trouble for a couple degrees.


Mike [

 

[Evans Ward]

Great question and post as I've wondered the same thing lately. I'm about 100 mi south of you atl gn and my SM2 reads about 170 on a 95 degree 90% humidity day. Those weather conditions would be about 98 degrees or so heat index... maybe higher? Sticky nonetheless. Good 'ol GA summers.... gotta love 'em! My VDO, which is electrical, always reads 10-15 degrees higher than SM2 readings. I do the glance thing with the VDO and check/validate with the SM2.

 

[turbo buicks]

atl gn, i only have an autometer elec. guage as of now so i cant yet compare SM2 #'s w/you. i usually get to about 195-205 @ idle on a HOTTT day. @ cruising speeds (45 mph) it ususally sets around 180-195. im almost sure from reading this thread that my guage is probably off a bit. my cooling system might also not be up to par. it looks a bit old, i might need a new radiator

 

[BoostMasterK]

Originally posted by Evans Ward
...My VDO, which is electrical, always reads 10-15 degrees higher than SM2 readings. I do the glance thing with the VDO and check/validate with the SM2.

And what do your gauges/SM read on the "thermostat check"?

Mike [

 

[Steve Wood]

Let's all take our gauges and sending units and ship them to SalvageV6. He seems particularly bored this summer and he would probably enjoy plunging each sender into a bucket of 195 deg water to see what the gauge read.

 

[salvageV6]

Hey cool, errr hot, real work instead of surfing the internet.

Only charge a nominal "handling" fee, shipping is free.

We still have a complete reliability lab. setup.

My mechanical gauges are accurate. 10 degrees is nothing with cheap electrical senders and low resolution gauges.

Can't say how accurate the factory thermistor sensor is but prolly better than the avg. electrical gauge.

I just worry when the numbers change from the day I install them, no matter what the gauge.

For your $40 handling fee you will get two test points 165 degrees and 200 degrees.

 

[atl gn]

Thanks guys, driving the car today the scanmaster temps ran up to 190+ with a 160 stat! Holy sh**! I have replaced my stat with a new one, and there was no change. My fan is working while driving--even if its running on low thanks to those great GM sensors, its not going to run that hot-especially while moving down the road.

Uh oh, I think it might be radiator time---
Got any good suggestions for one

 

[turbo buicks]

strange...my car does the EXACT same thing. maybe a radiator flush is in order. i want to hook up a manual fan control and run the fan on high all the time. i think they are available from www.casperselectronics.com

 

[Steve Wood]

Radiator flushing is usually a waste of time. Once there are hard deposits there, no flush will do much. By this time, 30-40% of the core is probably plugged up.

Put your hand on the bottom part of the core and see if it is noticably cooler than the top part. If the car runs in the 180s going down the road with the ac on, on a hot day, I would not be concerned about it. It will probably run more efficiently than the guy who is running at 150 and the engine will probably last longer.

 

[atl gn]

Yeah, I noticed that last night. The top of the radiator definately stays hotter than the bottom. So that means the bottom is plugged up eh? I have noticed that I cannot find a vendor who sells a replacement aluminum radiator with the oil and trans coolers inside of them. You would think if you are paying $600, it would be good to go--oh well! Any other options, it doesn't even have to be alumininum if it does its job.

 

[turbo buicks]

im pretty sure the stock radiators dont have integrated tranny coolers but they do have integrated oil coolers. my cars AC doesnt work so its never on and it still usually runs hot (190+) going down the road. is this a further indication of a bad radiator?

 

[Steve Wood]

Stock radiator, on the IC models, has both an oil cooler and a tranny cooler in the tank.

I would think running that hot without ac would be an indication that the core is going bad....most are that have not been replaced by now...or some of the baffling that forces air thru the core is missing.