My 1994 4.9L runs around 101-104C in 84 deg. F weather with the A/C on just driving around. Is 104C too hot for a 4.9L? What is the normal operating range for the 4.9L? What temp does the coolant have to be for the warning light to come on? Any info would be appreciated. Thanks.

My 1994 4.9L runs around 101-104C in 84 deg. F weather with the A/C on just driving around. Is 104C too hot for a 4.9L? What is the normal operating range for the 4.9L? What temp does the coolant have to be for the warning light to come on? Any info would be appreciated. Thanks.

Well if I knew the conversion, I'd be able to tell you. Switch the system over to standard (on the climate control panel somewhere) and see what the degrees are in Fahrenheit. It should run around 213 degrees Fahrenheit.

There is no way to switch it over. 104C is approx. 220F.

There is no way to switch it over. 104C is approx. 220F.

220 degrees is fine dude. If red lights start coming on for the coolant temps and such, then worry, but for now it is okay.

yah mine runs between 99 and 108 c you doing just fine dude ...

I would say it is NOT ok. It is the cadillac politic to design a car that operate very silence because customers want a silence and smoothe car, but more than 95°C for EACH car no matter if alluminium motor or not is too hot. Belive me - I already have killed two cylinder head gaskets on two cadillacs. I have my third Eldorado equiped with an extra switch on my panel so I can start the ventilator from inside. Cadillacs are programmed to heat up to 118°C befor starting the vent. And this is too hot. It takes about 40 minutes in stop and go traffic to get those 118°C befor the sensor starts the blower. This will kill each motor !!!

I would say it is NOT ok. It is the cadillac politic to design a car that operate very silence because customers want a silence and smoothe car, but more than 95°C for EACH car no matter if alluminium motor or not is too hot. Belive me - I already have killed two cylinder head gaskets on two cadillacs. I have my third Eldorado equiped with an extra switch on my panel so I can start the ventilator from inside. Cadillacs are programmed to heat up to 118°C befor starting the vent. And this is too hot. It takes about 40 minutes in stop and go traffic to get those 118°C befor the sensor starts the blower. This will kill each motor !!!

Your head gaskets blew for another reason: 213-220 degrees in drive at idle is NORMAL for these engines. Even our chief site engineer Bbob (designed Northstar and had a hand in the 4.x engines) has stated that both the 4.x engines and the Northstar engines run this warm and are fine with those temperatures.

My '87 Seville ran at the 213 degree area with nary a problem, as does my performance upgraded 4.9 liter engine. Even a friend of mine that owns a '95 STS runs this warm when in drive at idle.

When the air gets through the coolant flow, the engine will cool down from that while driving. When at a stop in drive, expect those temperatures: It is normal.

Yes, I know that this high temperatur is normal for a Cadillac but nevertheless it is too hot. No Buick, no Chrysler, no Ford, no European and no Japones car have this high temperatur. My Eldo runs with 90°C when air blows through the radiator.This is ok. Stopping in drive it climbs up to 118°C as every Cadillac do and this is pretty unhealthy for the head gaskets.

ok so what would you like him to do about the temperature ? is there a way we can scrub 10c off the temperature ? do not tell someone there is a problem if you do not have the fix , because your going to scare this poor guy who just wants to know if its normal ...

it appears your eldo runs exactly like my deville , tooling down the road i get down to 90c also ....so it appears to me your cooling system works exactly like mine

your talking a changeing the engine in a manner outside its desgin characteristics...which is dangerous...but if you have an idea to scrub off coolant temp in drive at idle on a hot summer day tell me ....

what is the normal temp now for cars ? cadillacs run a bit hot but not that much out of the average , which las time i checked was 190-200 degrees , not far off from the 210 we see in the cadillacs , hell i bet i can get the same 190-200 everyone else gets if i move the coolant temp sensor to another location ...the average coolant temp for a cadillac is claoser to the industary avegrage of 195 then it is to the indsustry average for danger of 240 ..

Plus remeber , we are talking about a engine with an alumium block , which in itself gets rid of heat too ....220 in a iron block car and 220 in a alum block are two diffrent things

you blew your head gaskets because the coolant wasnt changed yearly and you didnt use the GM coolant suppliment ....that is the single most important thing you can do with the iron head/aluminum block (4100/4.5/4.9 series) engines ...and its extra insurance for the nrothstars

i dont want to scare you off or offend you but i dont want you to scare twilight either ...

There are two ways to keep the temperature on a 90°C level. An expensive one and a cheap one. I selected the cheap one : I installed an extra circuit on my dashboard. Everytime I have to stop in drive for longer time and the temperature exceeds 100°C I turn on the blower by hand.
The expensive way is to installe an extra thermostat ( you can get them for older English cars like Austen Healey ) that starts the blower automaticily on 95°C.

There are two ways to keep the temperature on a 90°C level. An expensive one and a cheap one. I selected the cheap one : I installed an extra circuit on my dashboard. Everytime I have to stop in drive for longer time and the temperature exceeds 100°C I turn on the blower by hand.
The expensive way is to installe an extra thermostat ( you can get them for older English cars like Austen Healey ) that starts the blower automaticily on 95°C.

Where exactly do you put this extra thermostat? And how does an extra thermostat help to controll the cooling fans? Is this extra thermostat electronic as opposed to the mechanical one?

I'm totally confused with your post dude.

Now the fan override switch can be had at Jegs...But an extra thermostat? :rolleyes:

well its a thermostat for the fans , not the classic coolant thing ...

we used them when we retrofitted our airforce tow tractors from a mechaical fan to electric fans ....also bougth from jegs ...solid state units , i think the ones we had could be adjusted to a desired kickon temp ...its been years ago tho ...

i will have to agree with tomtom but its about GM in general , they seem to put off fan engagement till the last minute , our new malibu even waits too long before the fans kick on or kick on full blast ...

ill have to look into it and see if i can find those adjustable fan stats

heres the one i think we used
http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=110805&prmenbr=361

by the way , tom tom , have you run into any issues as far as the car flagging trouble with the fans ? if i remeber right the car issues a trouble code if it has issues with its fans..

also what did you do about backfeed into the circuit ? diodes?

Thanks for clearing that up Stoney. I would just purchase the override switch from Jegs before doing anything weird like the extra thermostat.

About the backfeed into the circuit I have installed an extra relay. This job has been completly done by an car electrical service (Bosch).

The adujustable temp control switch from Jeg's seems to bee the more confortable solution. I first have been looking for something like that in Germany, but nothing could be offered from BOSCH service.

bosch service ???

i suppose they came about to service there fuel injection systems over there years ago ?

I spent 45 minutes in frankfurt ..not long enought to see or learn anything ...

You don't want to trigger the fans to compete with the thermostat temp though, if the stat is a 92C stat (195 F) and the fans are trying to cool to 180 (like many aftermarket ones do that are intended for a cooler thermostat), it will never shut off. I am pretty sure GM triggers the fans late for fuel economy reasons (less electrical load), and possibly some improved emissions (that remains to be proven....). (BBob, can you confirm?)

But no, I don't like any car to run over 210F.

Maybe this is a great time for synthetic eh? (just kidding!!!)

There are two ways to keep the temperature on a 90°C level. An expensive one and a cheap one. I selected the cheap one : I installed an extra circuit on my dashboard. Everytime I have to stop in drive for longer time and the temperature exceeds 100°C I turn on the blower by hand.
The expensive way is to installe an extra thermostat ( you can get them for older English cars like Austen Healey ) that starts the blower automaticily on 95°C.
What do you mean by the blower? The coolant fans? Thats the way they designed these engines. I would say after extensive testing they figured this was the best tem that the engine could run at. Sitting at idle my 90 seville with the PFI 4.5 wont kick the fans on till it says 222 F on the info panel. At 233 F the fans go into high mode. My car has been this way since it was new and it now has 224,800 miles with nothing done to the engine but a waterpump. If you are having headgaskets problems then I would imagine the 10 degree difference is just masking the problem. I would suspect a surface irregularity in the head or block which is causing the headgasket to leak. I have had no problems and I have never used any of that coolant supplement crap either. But I change my antifreeze every spring, so that probably makes up the difference. I did notice that with the A/C on my seville on a hot day, like 90 degrees, will climb to 233. The fans go into high mode and it cools right down. Out on the highway without the air running it will run 198-205. A 195 degree thermostat is not fully open until 210 degrees. It starts to open at 195. Some people are mislead by that. However, I think that 220 should be normal. If it gets past 222 F while out on the highway, then I would suspect a thermostat not opening all the way. I sure wouldnt want to violate the vehicle electronics by adding a fan switch or thermo.

Blaze

Forgot to add that if this was a bad set-up then why has my car lasted this long? A lot of people I see have accumulated thousands of carefree miles without problems.

Blaze

220 degrees F coolant temp has absolutely no ill effect on the engine or the head gaskets. Geez...as much as these systems are tested you would think that someone might recognize an issue with the coolant getting above 90 degrees C....LOL LOL.

There is absolutely no reason in the world to try and keep the coolant temp at 90 degrees C.

If the system is operating correctly with a working 14 PSI pressure cap and a fresh mix of 50/50 coolant/distilled water the system will be in complete control and will not boil over until the coolant temp gets to 128 C or 265 F. The engine can actually operate at temperatures above that point with no problem so the engine nor the head gaskets nor anything else will be damaged until the temp exceeds 265 and the system boils dry and then gets much hotter.

If head gaskets fail in an engine it is due to other problems then the coolant temperature getting above 90 C....

There are millions and millions of 4.1/4.5/4.9 engines and Northstars running around perfectly fine with the cooling fans not even activating until the coolant gets to 225 F....that is perfectly normal and if damage were occurring then they would all be loosing head gaskets right and left. They don't.....

Thanks guys for the info. I appreciate it. Thanks Again.

I am new to Caddies and their design quirks.

Please explain the annual coolant change and "GM coolant supplement" ??



Is the supplement item pricey?? or reasonable??

Any generic products work - or not worth the risk??

Thanks in advance

Lets not go through this again.. Pink, search this forum for "coolant supplement" or "Bars leak" and you'll have abut a week's worth of reading!

You'll be an expert!
Peteski

The service manual speaks of drain plugs in the block. Do they mean the freeze plugs? Are you really supposed to remove those to do a complete flush?

Thanks,
Brian <long time since I posted>

Thanks for the suggestion of the forum

Sometimes some of us forget all the extra areas on this site.

The service manual speaks of drain plugs in the block. Do they mean the freeze plugs? Are you really supposed to remove those to do a complete flush?

Thanks,
Brian <long time since I posted>


The drain plugs mentioned are not the freeze plugs.

There is really no need to remove the drain plugs. Just use compressed air or the output of the shop vac to push as much of the coolant out of the block as possible and refill with fresh 50/50.

220 degrees F coolant temp has absolutely no ill effect on the engine or the head gaskets. Geez...as much as these systems are tested you would think that someone might recognize an issue with the coolant getting above 90 degrees C....LOL LOL.

There is absolutely no reason in the world to try and keep the coolant temp at 90 degrees C.

If the system is operating correctly with a working 14 PSI pressure cap and a fresh mix of 50/50 coolant/distilled water the system will be in complete control and will not boil over until the coolant temp gets to 128 C or 265 F. The engine can actually operate at temperatures above that point with no problem so the engine nor the head gaskets nor anything else will be damaged until the temp exceeds 265 and the system boils dry and then gets much hotter.

If head gaskets fail in an engine it is due to other problems then the coolant temperature getting above 90 C....

There are millions and millions of 4.1/4.5/4.9 engines and Northstars running around perfectly fine with the cooling fans not even activating until the coolant gets to 225 F....that is perfectly normal and if damage were occurring then they would all be loosing head gaskets right and left. They don't.....

did you guys put the iron heads on
for durability or to hold more of this
heat in the combustion chamber???

The iron heads were a design consideration to minimize costs and maximize durability. Remember that the engine was designed back in the late 70's and early 80's and started production in early 1981 as an 82 model. Back then aluminum cylinder heads were not that common, especially on high volume engines. The weight of the cast iron in the heads was minimized by making the heads very small in cross section...from the end they look triangular nor rectangular. From an end view the part of the head that is the intake ports is made up by the aluminum of the intake manifold.

The major mass in the engine, the block, was made of aluminum to maximize the mass savings by using the premium material.

Aluminum heads require that the valve seats be machined out and steel valve seat inserts by pressed into place. In those days this was still a bit tricky for a high volume engine. The cast iron head allows induction hardened valve seats machined directly into the parent cast iron of the cylinder head which is very very durable and very cost effective. Keeping the ability to make the valve seats out of the cast iron of the head adds to the cost effectiveness and the durability of the head and the minimized cross section of the head keeps the mass down by minimizing the amount of cast iron.

It had nothing to do with heat or retaining heat or anything else. Cast iron heads are very durable and excellent parts. The only reason for aluminum heads is for mass reduction. In a DOHC engine like the Northstar the heads are quite large so the mass penalty of making them out of cast iron would be severe so aluminum is used.

Some guy with a can of beer in one hand and a remote control in the other knows more than the engineer who designed the engine.

Some guy with a can of beer in one hand and a remote control in the other knows more than the engineer who designed the engine.
What engine doesnt have aluminum in them now a days?

Blaze

How about running the car without a thermostat to stop high temps in the summertime? or will that harm somthing?

By George, another scientist!

How about running the car without a thermostat to stop high temps in the summertime? or will that harm somthing?
Then the engine may not warm up enough to go into closed loop which would make economy suffer.

Blaze

Running without a thermostat may cause as many overheating problems as with one that is bad. The thermostat is a calibrated orifice in the cooling system, it restricts coolant flow so that it doesn't pass through the radiator too quickly, not passing off as much heat as it should.

For example, if the radiator as designed with a proper factory spec'd thermostat is expected to give off 50000 BTU's of heat in a normal pass of the radiator, and you make the coolant flow FASTER, it may not have sufficient time to pass that heat off, and may only pass 25000 BTU's, therefore the additional heat is sent back to the engine to be heated even more by the engine, which is expecting to have the coolant down to a certain temp before it comes back for more. These numbers are purely fictishous, I have no idea what they actually are. Only a GM Cooling system engineer would likely know.

As for not going into closed loop, my experience is coolant temps need to be below 150, possibly even cooler to have an effect on closed loop operation. I suspect GM engineers knew people would mess around with cooler thermostats and ensured that they would still go into closed loop even with a cooler one to keep emissions somewhat in check.

The speed of the coolant going through the circuit has nothing to do with the heat transfer abilities.

Keep in mind that if it runs "too fast to lose heat" in the radiator, it consequently runs too fast to pick up heat in the engine.

Speed of running coolant is not relevant.

And why are Cadillacs delivered to Europe have an improved and optimized coolant system (and reinforced transmission) ?


Because we have a very different traffic situation. A regular Cadillac imported from the States, without improved radiator will overheat on our autobahn.

These motors are designed to drive from eastcoast to westcoast but not for the daily overkill on our fu..... autobahn.

The speed of the coolant going through the circuit has nothing to do with the heat transfer abilities.

Keep in mind that if it runs "too fast to lose heat" in the radiator, it consequently runs too fast to pick up heat in the engine.

Speed of running coolant is not relevant.


uuhhh.....wrong.


tony and NODIH....I hate to break the news to you but the speed of the coolant flow DOES have something to do with the cooling efficiency. Basically...the faster the better. Any engine cooling engineer in the world can verify this for you.

Trust me, the coolant has plenty of time to "give up heat in the radiator" and "pick up heat in the engine" no matter how fast it is moving.

It really is an old wives tale (that is totally false) that slowing down the coolant helps the cooling system. I think that got started eons ago when hot rodders started revving stock engines past where they (or their water pumps) were designed to operate. As a result the water pumps cavitated, stopped pumping and the engine overheated. Someone got the idea to slow down the water pump with a larger pulley on the water pump and the engine quit overheating. So....they invented this idea of "slowing down the coolant so it has time to pick up the heat and give up the heat". Trouble is, the reason the engine no longer overheated was because the water pump was pumping again and not cavitating like before....it had nothing to do with speeding up the or slowing down the flow rate.


Theoretically, it is easy to argue that the mass flow rate of the coolant doesn't matter. Trouble is, that doesn't take into account the efficiency of the radiator and the "scrubbing" effect of the high velocity coolant inside the engine.

The greater the temperature differential across the radiator (the radiator fin temp to the air temp) the more efficient the heat exchanger is. The faster you move the coolant the higher the temp of the fins on the cold side so the rad efficiency goes up and the system cools better.

Inside the engine, at the hottest spots, bubbles can form on the hot surface...called nucleat boiling. Those microscopic bubbles on the hot surface tend to isolate the coolant from the surface and reduce heat transfer. Faster flowing coolant scrubs the bubbles away and promotes more heat transfer to the coolant thus reducing engine temperature. High flow is good.


Modern engines move the coolant at a very high rate. The higher the output of an engine the faster the coolant flow. The coolant pumps are designed for very high flow rates at high efficiency so as to not sap too much power from the engine.


It is not desirable to run without the stat in general because of warmup and such. With the Northstar engine, in particular, the stat is an integral part of the flow control of the system and the sytem will NOT work correctly without the stat in it and it will NOT have the maximum cooling efficiency.

Having said that....with the 4.9 engine the stat is a fairly simply device that simply controls to a temp and it is NOT part of the integral flow control of the system. Removing the stat will usually help the cooling of the system due to the increased flow in a 4.9. This is true only for a maximum effort cooling situation where the stat is fully open anyway. Removing the restriction from the system will help slightly if that were the only situation the engine had to deal with.


NODIH, the problem with your reasoning is that you forgot to include the part where a much greater volume of coolant would go thru the radiator in the same time period. True, per your example, on a single pass an individual slug of coolant would give up less heat in the radiator but without a given time interval more slugs of coolant would pass thru the radiator with a faster flowing system thus the total heat transfer would be the same in that simplistic example.

As I indicated earlier, that slug of coolant would pass thru faster and would give up less heat and would exit hotter....so the end fins would be hotter in this case than in the slower moving coolant case. THAT would improve the heat transfer capability of the radiator by increasing the delta in temperature between the fins and the air coming thru it....thus the overall cooling efficient DOES get better with faster flow.

Trust me, I have done lots of engine cooling development and have seen it proven over and over that the more flow the better. It isn't even up for debate. Slowing down the coolant or orificing the system is NOT the correct thing to do for cooling efficiency. If someone makes a mod like that and it "improves" the cooling of the system then they had something terribly wrong elsewhere and they are not fixing the problem by slowing down the coolant..!!

And why are Cadillacs delivered to Europe have an improved and optimized coolant system (and reinforced transmission) ?


Because we have a very different traffic situation. A regular Cadillac imported from the States, without improved radiator will overheat on our autobahn.

These motors are designed to drive from eastcoast to westcoast but not for the daily overkill on our fu..... autobahn.


uhh....wrong.

Export cars get the same cooling package and transmissions as the domestic cars do. I hate to make you think that your car is "nothing special" compared to the US cars....but....it isn't.

High speed cooling on the autobahn is actually not that stressful. True that the engine is under high loads and high speed but the vehicle is also moving very fast and the ram air at those speeds offsets the additional load. All the cars, whether for the US or Europe, are cooled for high speed operation. If you think the Europeans have a monopoly on high speed driving then you have never driven across Texas or in the desert south-west of the US...or across Montana. Speed limits or not that is some very desolate country with some pretty straight roads and the speeds rival anything on the autobahn....LOL.


The hardest cooling situations can be the city traffic, stop and go, 105 degrees F in Phoenix, Arizona that the US cars have to contend with on a daily basis....or city traffic in Florida at 100 degrees F and 100 % humidity and full AC load....or flat out from Baker California to Death Valley at 110 degree F ambient.

---------Hey not for nothin guys i ran my cad today without the stat and it ran in temp zones like ive never seen befor! in a good way!
With the stat: it ran about 195-225
without the stat: about 175-215 (whille driving with the air flow helpin}
-----But it did reach to 225 in traffic due to the shitty fan run time!
Thus my cooling battle carrys on. I think next thing is to get the override swich. Bob is mostdef right thought,.
and yes i had already put in a 180 stat and it dident do dick

How about running the car without a thermostat to stop high temps in the summertime? or will that harm somthing?
A cooler stat (say 180 instead of stock 195) will bring highway temps a few degrees down. Same thing obviously with driving without stat. But when it comes to 200 plus any stat would be open anyway and does not affect the cooling performance. Now things more depend on fans. Perhaps, removing stat will increase the flow but I really do not think you'll get any dramatic change.

I have installed a 180 stat and now highway temps are 186-188 instead of 194-196 before (with stock stat). But in traffic it is 220 plus anyway untill the fans kick off. I change the stat intentionally since I have EGR related spark knoch when engine is hot, so some8-10 degrees make some difference and at least make me feel better.