Cooling System Re-do

[jfrawley]

The cooling system on my '82 Spider looked to be original and a bit erratic, so I decided to update. With the help of a friend, we replaced radiator, fan relay switch, T-stat, water pump, all hoses, belts, clamps, and gaskets. With the exception of one of the water pump bolts breaking off in the block (3 hours lost), all went well. We followed the burping proceedure others have detailed here, and as spelled out in my manual and it worked perfectly. Now the question.....the fan comes on and off as it should, but the gauge reads about 220 when it does. Any thoughts? Gauge, sending unit?

John

[kristoj]

John,

It could be that the gauge sending unit is not working properly. However, I don't think it is unusual for the fan to kick in somewhere north of 190. Mine kicks in well before 220, though. I would first check the engine temperature with a laser thermometer to get a true reading. You may find that it is indeed the sending unit. If the temperature really is 220+, then you need to check that the thermostat is installed correctly (easy to get it backwards) and the system has indeed been purged of all air pockets.

[mbouse]

i concur with the suggestions made, the gauges on your car are NOT, repeat NOT known for their accuracy. But, unlike Lucas equipment, the Veglia brand actually function on a daily basis.

you can and prolly should try a different temp gauge. Delivered to your door for prolly under $20. for future reference, the sensors are also readily available and inexpensive. in the mean time, make sure all electrical connections at the gauge and the sensors are clean and tight; ESPECIALLY the ground wire.

and, i read an article in an auto magazine (non-Fiat related) stating that one of the prime tools any mechanic should purchase if concerned with coolant system upgrades is a laser thermometer. that article stated that they are relatively inexpensive, under $30. i've not had the opportunity to verify this claim, but it does not sound unreasonable.

so, my question is.... how accurate is that stinking thermometer? i mean, you point it at the OUTSIDE of the radiator, or the TOP of the head. how does that translate to tempurature of the coolant INSIDE the radiator or UNDER the head at the sensor? shouldn't you need to compensate for the distance between the outer edge of the metal and the inner surface that is actually wet with coolant? what amount of degrees do you add for a 1/4" of aluminum or rad fans and the density of the cooling tubes? certainly there is heat loss between the atmosphere side of that metal and the coolant side.

[baltobernie]

Hello J. Frawley,

My 1976 1800 engine reads 205°F between the blades when the fan kicks On, and cycles Off at 195°F, according to a non-contact thermometer. The top of the radiator near the upper hose inlet reads as high as 220°F during idle. The dashboard temperature gauge reads approximately 200°F during this process.

I don't know if later models were designed with higher coolant temps, like many other manufacturers. The big question is what your gauge read before you swapped everything out. You're welcome to borrow my thermometer for the price of postage, but they're almost too inexpensive not to have one. http://www.harborfreight.com/cpi/ctaf/d ... mber=93983.

Mike, I think their benefit is the ability to measure different locations along the radiator or cylinder head, for example.

[rlux4]

Bernie, Could I ask why you chose the non contact type over the infa-red? You're right, definately cheap enough to own one.
Ron

[manoa matt]

Non contact, laser, infra-red..... all the same thing. Radio shack also has them for pretty cheap.

The sensor in the head is surrounded by aluminum, only a small portion sticks out into the water cavity. Aluminum is a very very good consuctor of heat and I wouldn't be supprised if the temp only varies a few deg from inside to out. Anyway its the metal temp of the head you want to monitor.

All the cars were designed with the same thermostat temps and rad fan switch temps, however we all have different cars and live in different areas. Some people have made modifications, while others have not. No one on this site will have a running temp the same as the next guy, you just have to drive and watch the gauge to know what is normal for you and your car.

My cars temp is pretty steady, but my friends fiat's temp swings a few deg from idle to 30 mph. Of course I have a new re-cored 3 row high effeciency radiatior and he has the original that is probably partially blocked or silted up.

Several things will determine your cooling system normal opperating temp or efficiency:
Water pump impeller design and efficiency
radiatior design and efficiency
belt slippage, or increased or decreased water pump pully size, also crank pully size
location and function of thermostat
location and functionality of rad fan
use of front air dam, or windage tray
Front vallance design (some cars have two grill areas providing more air to the lower portion of the rad)
coolant type, mix porportions, and age of coolant

Elimination of heater core and re-routing of hoses will provide more consistant and cooler temps to the back of the head.
Ignition that is too far advanced will increase head temps.
Improper air/fuel mix can also increase head temps.

[jfrawley]

Interestingly enough, the temp gauge is acting just about as it did BEFORE I put in the new rad, T-stat, water pump, etc. The one thing we didn't change is the sending unit. I will change that out next. Bought an infrared meter tonight and will check it out tomorrow night. I will also clean the grounds as Mike suggests and report back. Thanks all.

John

[baltobernie]

definately cheap enough to own one.
Ron

Ouch! That hurt, Ron. Is this trash talk typical of all '82 owners?

[jfrawley]

OK, so now I feel better. Took her out for a ride tonight, got it up to full temp, and checked the engine with my new infrared thermometer. At idle a nice 188 degrees; fan came on at 205; off at 185 (all measured on the heads). While all this was going on the gauge was reading 200 at idle, 220 when the fan came on. Guess it's the sending unit, gauge, wiring.....or all three! Thanks for the advice, you guys are great.

John

[rlux4]

Bernie, No way man! I don't even know how to talk trash, except when I say "yes dear" when my wife says take it out.
"Cheap enough" is purely speaking for myself. Something under $20 I can usually talk her into, get over that amount and she balks. Something to do with using the money for bills and groceries. I don't understand her: pay bills or buy a new tool... seems like a no brainer to me.
Ron

[baltobernie]

just pulling your lariat, bubba

[baltobernie]

Hey John,

Now that you're satisfied with your coolant temp, why not join us on Sunday? http://www.dcfiats.org/events/index.html The ride begins in Frederick.

[rlux4]

just pulling your lariat, bubba

I know, that's how it was taken, and I sure can't complain if someone pulls it if I leave it hanging out there!
Ron

[majicwrench]

Non-Contact thermometers are NOT very accurate. As mike wondered, it depends a great deal on the surface at which they are pointed. If I recall, it's refered to as "reflectivity" or somethign like that. Pointing it at a black painted surface, and a aluminum surface, both at say 200F with a contact thermometer,, you are going to get different readings with the non-contact. I read a rather technical article about all this a few months back and could probably find it again if anybody is really iterested. But still, for what we are using them for they are a GREAT tool.
Keith

[jfrawley]

Bernie, I too am a member of DC Fiats but it seems every time we have an event, I'm out of town. Ditto for this weekend. It's a great bunch of folks and I wanted to be there for the ride. Hopefully next time.

John