just acquired a nice 87 and I am new to vets, what would be a normal coolant temp in summertime running with some aggressive driving??

 

Mine runs around 190 but will quickly rise (by design) to 220-230 sitting in traffic. The aux. fan kicks in at 235.

 

I installed a switch that allows me to run my fan any time I want. Easy to install and will keep your car running at a cool 185-190. I also installed a new motor on my fan. Runs like a banshee and only cost $25. That will fix your problem for good. I bought switch at Walmart. Make sure your new wires
leading to the switch are about 10 gauge or you'll burn them up.

 

My 87 use to be in the same ball park until I changed the thermostat and sensor to a 160 degree. Now during Florida summer heat with top down at stop light with A/C on the temp is around 225, underway it is around 195-200.

Also note, in doing some data logging I noticed a huge difference in my PCM temp versus the dash gauge. My PCM was running roughly 15-20 degrees lower than what the dash displayed.

If you can do it, you might want to do some data logging and check if you have a similar discrepancy.

 

First thing you should do is to check the front of the A/C condenser for dirt and debris. Also check the radiator for the same. Once stuff builds up between the fins and the tubes, you can expect a loss of airflow and a rise in coolant temps.

Use a garden hose to spray water from the engine side of the radiator to loosen and remove all the gunk. Can't hurt to vacuum between the two units first. Does the car have the RPO KC4 Auxilary cooling fan? Look for it up under the nose in the opening behind the front facia.

Do you have any history about cooling system service? The car uses the green ethylene glycol coolant and water. Don't ues or mix the orange Dexcool! I'm not a fan of the universal coolants either. It can't hurt to do a cooling system flush.

I have a 180 degree 'stat in my mildly modded '87 and I never see temps above 190 even on hot days whether or not I'm in city traffic or on the freeway. I have done track days with the car where the air temps have been over 100 and on-track coolant temps will be 200-215.

I'm not a fan of running the fans off a switch. C4's are designed to run hotter than some other cars as it helps to reduce emissions. Seeing temps of up to 225 is normal with a cooling system in good condition.

 

yep...

C4 is designed to run without the help of a fan BUT it has one to fill-in when you sit still in traffic. During those times expect to see 235+ if the ambient is 95-100.

As soon as you roll again and maintain 35mph or more...temps fall to 190ish.

The above mentioned 180 stat also works best for my modified 87 that's prone to over heating because its bored to the limit of the block...The 160 mis TOO cool and causes other issues. Fans are managed by the ECM and temp senders....the fan ON timing MUST match the T-stat otherwise fans run more than needed and wear out, or they prevent the engine from completely warming up to meet the expectations of the "tune" in the ECM.

 

Please elaborate further as I am not sure what issues would be caused by the 160 T-Stat. I am not seeing any issues but am curious if I am blindly ignoring them as they are not overtly obvious....

 

My switch allows me to use fan at will. I wouldn't sit at a stoplight and watch my coolant jump 40 degrees. Switch is the way to go with 180-185 tstat. Only use switch as needed. No need to run all the time. I only use switch in traffic and while using ac. Constant temps result in less problems than a system that fluctuates 40 or more degrees. Brand new fan motor is only $25. Cheap price to pay for

 

The Number 1 reason is the over-all health of the motor. if the oil temp never climbs to 200+ and stays there for a while to boil off the moisture that collects there every night from normal hot/cold/hot condensation that forms in the engine, the oil holds that moisture (water) and it turns to sludge and it forms acids that help destroy the fine metals used in bearings.

No need to argue that they ran engines at 160 and got away with that back in the 60's....They DID ! ! !

they also rebuilt those engines from that era at less than 100,000 miles. Engines were toast at 100K because the internals were worn out and the bearings shot. Hot oil is the solution. Today we get 200K or MORE out of an injected engine.
They can go 250k or even more. That's because of the heat and the fine level of fuel management.
My current engine that is a rebuild has in excess of 200,000 miles on the motor, and it uses mebbe 1 pt of oil per 3000 miles. I go up to 5000 on synthetic oil in winter, and 3000 to 5000 in summer depending on how the car has been driven....lots of short hops get more frequent oil service BECAUSE the damage to the oil is worse when it never gets HOT enough....when I do longer trips, I will run that oil longer since its cleaner from being able to be hot enough.

Hot oil boils away the water. The oil last longer, does its job better.

Next would be the emissions themselves.. same basic principle. When the whole fuel charge is burned each stroke, there is no (less) residual fuel, (gas, which is a solvent) to linger in the cylinder during full strokes and wash away the micro-thin layer of lubrication on the cylinder walls.
the HOT engine at close to 200+ degrees helps burn that fuel charge so there is nothing left,. or as little as possible. That aids in the longevity of the engine.
the tune comes next. We KNOW the optimal air/fuel ratio for gasoline is 14.6:1. That is best utilized for the maximum performance at higher temps. This maximizes the performance and minimizes the emissions. Nobody WANTS to make more smoke...but we DO want to make more power, so the right way is to use the science to do so and have the best of both worlds...most of the time at least.

The engine ECM uses fixed parameters to maintain this AFR to maximize the performance and heat is part of that. If it was a track car and there was no concern over the life span, you could toss that AFR and yes, you CAN find some more power with a richer AFR, BUT you WILL sacrifice the engines lifespan and reliability in the process. Rich mix means lost lube. It might run like a bat outta hell but it won't run like that forever if its washing the oil off all the internals from the excess fuel in each cycle. Plugs foul, spark is more difficult with excess solids building up on the electrodes. Carbon. Carbon causes detonation.....sometimes leads to damage to the pistons dome from an ever present hot spot. AKA as a "holed piston". Carbon is the direct result of excess fuel or oil that's left unburned...often from too low operating temps. True, high temps can be a part of "ping" or knock, but ONLY when an engine is out of tune. These things were designed to perform at these temps in excess of 200....if they are in decent shape and you buy good gas they don't knock or ping.

I was a victim of the "old school" mentality for a long time in So Cal where the temps were very mild and the temptation to do things like run a modern EFI engine at 160 all the time did get me for a while...until I saw the damage and PAID the price for being ignorant. I used to have the 160 t-stat and we ALL KNOW the cars run wonderful when they are semi cold. We assume its because they are cold...sort of. Its because they are on a little bit more fuel and the colder intake air is helping too. I ran my first one at 163degrees at cruising speed for a long time until I saw the insides and got a severe a$$ chewing from a well educated SBC guy that was repairing some damage that I did out of ignorance...
if the engine is well maintained and its in good shape and the "tune" is designed for "normal" temps of 195 to 225...it WILL run just as good there. We most often see a drop off in engine performance when they get hot because there is something wrong...not because its hot. Once I rebuilt my motor and got lots of mods and a bunch of over sizes....it was going to run hot no matter what I did, so I had to accept the fact that there really IS a MINIMUM normal operating temp that's best for all concerned and 180 is about it. My fans come on just before the stat opens so there is lower temp water available to circulate but its NOT cold water compared to what the block is discharging....that's bad.

Because the fan ON and the stat need to be working together...otherwise the hot coolant in the block is waiting to circulate while coolant in the radiator is getting over cooled, and sometimes this can lead to a heating problem that's not a TRUE overheating....its poor coolant circulation.
True, 40 degree temp swings are very hard on an engine that's part iron and part aluminum,. very hard on high stress parts like gaskets...(head gaskets) as the metals have different expansion/contraction rates. its tiny. BUT it can make a difference in a delicate place like a head gasket. So, its better to stay at 200 than it is to cruise at 160 and have the temp spike in traffic as it WILL, with a fan switch, a polar bear blowing in the nose or whatever you have to help...the temp swings do more damage than a stable temp that's higher.
mine stays at 195 for the low, and will go as high as 230 under the worst conditions....it CAN go higher but that's only under the absolute worst conditions where I can assure you that yours, or anyone elses would also do the exact same thing. There WILL be somebody that says their car won't do that.....never gets over 200 for any reason. This person will be posting from SoCal or Anchorage.

Then again, mine is not stock and Its expected to run hot. After some hard lessons, I do not "push" mine when the temp is below what the normal temp of 190ish is, nor do I force it to warm up faster by revving or driving in a lower gear to spin it harder and generate heat faster. That's a fools game... I allow it to warm at its own pace in summer and in winter It does not MOVE until its got at least some measurable temp, usually at least 135 where the ECM thinks about going CL and the engine is getting heat through all of its parts.

heat was the enemy 40 years ago. Today, stable temps are the goal and heat can be utilized to help do good things because its there, we have plenty of it and its better to work with it than it is to battle it. Heat will win that war because it is a natural byproduct of the engine. Why not make use of it?
Its unavoidable. so we have to use it for the certain benefits that far outweigh the downside.

The BIGGEST downside to running "normal" temps of 200 degrees is that this number is closer to the limits and it gives US less of a margin in case of a blown hose at hiway speeds or when you are trapped in the middle of the freeway, on a hot day, traffic stopped, and you blow a hose and the steam is gushing out from under the hood....as your temp gauge tells you that you have about 20 seconds at most to do SOMETHING ! Shut down, pull over, something. Otherwise....its gonna be an expensive day.
When your "emergency" begins at 230 you have only seconds to react. Often that's not enough. If you are only at 170 you have a much bigger window of opportunity to do something....lots less stressful on YOU and the Motor. That's why we think we need to run cooler. No other rational reason.
I have been trapped in traffic like that....scared the $hit out of me. I have seen my engine go past 270 degrees. I thought I was gonna die. I KNEW it would seize or something....it didn't. I don't EVER want to do that again...so I do the maint and change hoses BEFORE they blow and I keep the engine nice. It repays me by letting me off the hook in these break-down situations of blown hoses and such...The trick to surviving these situations is to AVOID them in the first place !

Hope this helps. I'm positive that someone will argue this and that's fine. To each his own...
I use the science and what my personal experience has been and what is well known...cold temps cause problems with oil, moisture from condensation, with emissions and the metals. ALL that is fact. Not opinion.
That's enough for me to want a hot engine that's simply "tuned" to run well at a reasonable temp of around 210 avg. Like yesterday for example...it got up to 90 and I was sitting in traffic idling with the a/c at 232....5 miles later at 55mph it was back down to 200 and eventually went down to 197.....the brief spike of 30 degrees is not a death sentence. That has a LOT to do with how sudden it is. If that were to drop from 230 to 190 in 30 seconds...I can HEAR the clink of iron cracking.......
but that temp lowering naturally over a few minutes...is not the least bit harmful....just like the warm-up that's natural. Either way, the temp swings CAN take place...at a reasonable length of time...not quick. That's death. I think that's where folks get confused....its more a matter of TIME than temp.

 

Thanks for the clarification and after reading I feel good about my 160 T-stat. The reason being I am in Central Florida and even on a cold day my temps run 190-200, on warmer days I am over 200 so I believe for me this is going to work out well.

For those in colder climates it is probably a greater concern.

Thanks again, I appreciate the insight.

 

In a stock / near stock engine a 160 stat is fine as long as the tune is adjusted for it.
**With a proper tune** you won't have any ill effects other than:
- Emmissions
- Heater output will be lower

btw rule of thumb, 40% goes out the exhaust, 40% goes into the coolant, and 20% goes into the engine room air.


(I'm a genuine automotive cooling expert & have tuning experience too )

 

Targeted A/F is a function of load, exhaust valve temp, and observed knock. Also, stoich for current fuels (alcohol blend) is actually lower than that.

 

Shhh, don't get to technical, or there will be another 4 page posts that means absolutely nothing. AFR is dependent on many things. While 14.7 works great on a street engine in light load operation we all know 12.5 is lean best torque for WOT for gasoline. This can change with more aggressive cam timing too.