Coolant sensor, wiring, or other?

[JetBoater]

My new motor is running well, but the factory gauge barely moves after the engine warms up.

I had installed the original coolant temp sensor which worked fine in the old 6.5... I removed it and used another one I had in the shop... and got the same result. This sensor is located on the front of the drivers side head.

I purchased a brand new sensor and the gauge still doesn't provide a reading. The needle moves to the first hash mark of 40 degrees C. The old one read just below 100 degrees C (middle of gauge).

The green wire shows 13+ volts, and when I ground it, the temp gauge swings fully to the high side.

I did install dual 180 degree F thermostats... so the temp should be around 80 degrees C.

Can anybody provide some advise?:(
Thanks,
Mike

[More Power]

With 40 C, you should be able to keep your hand on the thermostat housing without getting burned. Unless you have a handheld IR thermometer, this will help you determine whether it's actually 40 or closer to 100. To avoid getting burned, just momentarily brush the housing with your fingers to see if you can keep them on longer.

Jim

[JetBoater]

It feels hotter than 40 degrees... I can hold my fingers on the thermostat housing for a 5-6 seconds before it is uncomfortable. I will check it with my infrared thermometer tonight.

Somehow the sensor isn't providing the correct reading to the factory gauge. It seems the 180 thermostats have thrown the factory gauge out of whack..:confused:

I have priced out the triple pack of Autometer aftermarket coolant/voltage/oil pressure gauges... $170. Maybe this is the best option unless anyone has better options.

I pulled the factory gauge console out yesterday... all the connections to the mylar circuit are intact and clean.... I could not see any areas of concern.

:confused::confused:

[JetBoater]

OK... I installed a mechanical temp sensor into the water pump... as it had a big 1/2" fitting and I didn't see a better place to install it. Should I get a reduction fitting to allow install into the head?

It was pouring rain and I just wanted to get the job done.... The test drive showed 140 to 160 degrees (coming out of the radiator after it is cooled).

The factory gauge must be bad.

I installed a mechanical Oil pressure gauge at the same time and it showed 60 lbs cold. 30lbs at hot idle and 60 lbs under acceleration.

A Volt meter was also installed...

[rhsub]

The water pump is on the cold side of the cooling system so 140 to 160 would seem to be a good temp, this temp would be greatly affected by the outside air temp. I would put the sensor in were the factory sender is (front of left cyl head) or if possible in the thermostat crossover manifold (this is the best spot if there is a port available). coolant flow through the engine is water pump, block, heads, thermostat, rad. Hottest spot is before thermostat. I am not sure if the computer in a 93 has coolant temp in it, is there a 2 wire sensor in the t/stat manifold, if so install a scan tool and road test, this is the easiest, cheapiest and most accurate way of checking engine temp
good luck
Ron

[JetBoater]

I removed the factory sensor and reinstalled the mechanical temp sensor in the stock location last night. After driving it 30 minutes to work this morning... it read 160 degrees F hot and 150 at an idle. Ambient air temps were 3 degrees C or 37 F.

Are my dual 180 high flow thermostats working too well? Should I put 195 T stats in instead? :confused:

I am getting hot air in the cab... not roasting hot, but hot. This is primarily a tow vehicle for my 4000 lb aluminum jet boat... with a camper on the back in the summer months.

The big question.. is it bad to run cooler and how will this effect the longevity of the motor, mileage, etc..

All expert advise appreciated.

By the way... I just thought about this... I run my 400 HP Chev 350 jetboater motor with the same thermostat... It runs between 160-180 degrees F. It only has 30 hours on the powerplant so far and seems happy. It cruises at 3200 rpm, with wide open throttle at 4400 rpm.

[More Power]

I was told some years ago that Peninsular installs 160 degree F t-stats in all of their marine engines. I ran a 160 t-stat in my first 6.2 for several years. It would produce 24-mpg, and deliver more heat than was required in the cab, even in -20F temps.

Thermodynamically, more heat theoretically improves efficiency. But, there are lots of variables, that when combined, determine which is best (such as how the truck is used, where you live, fan-clutch engage temperature, and so on).

During the winter and cooler temps, the Duramax trucks I've driven all run below the t-stat setting when running unloaded. These engines use a 180 & 185 degree t-stat pair.

If you're using Robershaw, Mr. Gasket or an equivalent hi-flow stat, it may not seal as well as a GM ACDelco t-stat, which in my experience is not a big deal. The ACD t-stats are made using a rubber coating on the water control valve that seals better when closed.

Jim

[JetBoater]

Jim...you know what... I think you have a point with the thermostats sealing...

I'll open them up, as I fear my budget mechanic installed them improperly.... he either did not use the rubber seals or installed them wrong.

The t stats should be sandwiched in the middle of the rubber seals... he may have install them incorrectly, leading to bypassing before temp is reached.

It really is a pain having to recheck everything and trouble shoot little issues.

Thanks! ;)

[Kennedy]

In the past, I have found debris lodged in the opening of my stats causing low operating temps. This was on a fresh reman in cool operating temps so it never got warm enough to really open the stats. Also, the RS high flow stats have a bit larger "bleed" to them. It's a small engineered "dent" in the rim. The AC Delco units have a hole with a small anvil through it that makes the opening area very minimal.

[JetBoater]

I pulled the dual T stats yesterday and found they were installed properly. I found no obstructions or anything abnormal.

The Mr.Gasket High Flow 180's work a little TOO good coupled with the fresh 4 core radiator and larger clutch-fan.

I did a 70% diesel coolant/water mix... also.

I will monitor the temp and see if it falls into the normal range as the weather warms up. I have no doubt it will.

Thanks for your input!
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