Firebird1984

I posted this under the electrical area since the gague in question was an electrical water temp gauge. I'm reposting here in the cooling area as it also relates to cooling.

Ok, here's the deal. I just installed a new crate engine and during the break-in the temps got up to about 220. Kind of high, but not unheard of for a tight new engine. I have the original dash temp gauge and a new sender in the driver's side head. They changed the size of the hole and threading in the head on these new crate engines, so I had to get a brass bushing to adapt it, but no problems there.

Well, I put in a new GM thermostat that I tested in hot water, so I know it opens fine. I didn't have a temp gague in the pan of hot water, but it opened well before the water started to boil, so I am taking it that the 195 degree stamped on it is at least somewhat accurate.

Ok, help me interpret what I'm seeing here. I do remember that the old engine used to hit about 220 before the temp would drop and it would stay below the 220 range in normal driving. The new engine and sensor do run up to just on the high side of 220 and I notice the temp drop back. My thinking is that I'm seeing the effect of the thermostat opening at it's rated 195 design temperature.

Ok, I am guessing that this is telling me that my gague is inaccurate and the 220 I'm seeing on the gauge is actually closer to 195 degrees as that is where I notice the temp drop when the thermostat opens. Am I right on this? If so, I will not get bent out of shape while driving around town and the temp is at 220 or a bit higher as this means I'm really at something like 200 degrees and should be in the safe zone. Am I interpreting this right or am I mixed up?

I am seriously considering putting in all new Autometer gauges in this thing and making a custom panel for the dash in the future. Anyone else notice temp gauge inaccuracies on their ride?
Thanks for any input or observations.
Brad

tagta189

no,what you are likely seeing is the factory systems not turning the fans on till 222 degrees.That is if you have a tpi.if not then yes the gauges are probably off.possibly both..

Firebird1984

Thanks for the reply. No electric fans here, just a mechanical flex fan driven by the engine.
Brad

91black5spd

The gauge in my car is not linear because the first half goes from 100-220 and the second half from 220-260 so it is hard to accurately determine the temp from the gauge because the dashes are not all the same interval. However since you have a marking labeled for 220 it might be correct at that level. Anyway I don't think our gauges are really that accurate.
Also, your thermostat may start opening at 195 and be fully open ~215. The stock one is labeled 195 but this is the normal temp it will keep the car at. It actually starts opening a little earlier ~185-190 and is fully open ~210-215 so that the car stays around 195. Some aftermarket companies might label the stat by the initial openning time which is I think how 160 and 180 stats are labeled. If you are worried about overheating just try running a 180 stat.

naf

iTrader: (7)

First the factory temp guages are highly inaccurate and second, you're attempting to compare temperatures at two different places. The guage sender is on the head and subject to hot spots and potentially higher temps than the water neck. If you still have the ecm controlling things, you can have a shop plug into the ALDL and tell you what the CTS in the water neck says the temp is and compare it to the dash guage. If that's not an option, you can try an aftermarket temp guage plugged into the water neck. Otherwise, you'll have to develop your own empirical knowledge base in order to tell what dash temp reading is "OK" and what is "Too Hot".

Firebird1984

Thanks for all the good feedback. I ended up getting a new aftermarket gauge and plugging it into the intake port near the thermostat housing. It never goes above about 190-200 or so. I am thus assuming that the stock gauge is inaccurate and that the 220 it's reading is not a problem. I'm leaving the aftermarket gauge installed as a backup to the stocker, just in case.
Again, thanks!
Brad

Stekman

Yea, the factory gauge is quite inaccurate. Nothing new there.

Forshock 85TA

I thought i was getting hot (just below red)

Changed it all, new fans, stat, installed 180 stat it opens when my temp gauge says 230+ closes when just below 220.

So using that im about 40* off!!!

External gauge recommended!

Firebird1984

Glad I'm not alone in this gauge inaccuracy thing! Thanks much for all the replies... I feel better now!
Brad

Forshock 85TA

actually did more testing today

My gauge temp sensor (drivers side head) shows about 240* using the "ohm test", gauge shows ~220. No way is my engine that hot, no boil over, i can touch the hose real quick. Maybe the gauge is "calibrated" for external heat from the exhaust and drops it a little even though the engine is not that hot.

BTW, to test i had my fans on high (2-speed), let engine warm for about 10 minutes, stayed at 220 for about 3. Basically about thermostat temp the whole time.

In Short: temp gauge and sender are inaccurate? Anyone know how to measure the CTS for the ECU?