: n* experts chime in

STS 310
02-26-06, 09:22 PM
Would a n* operating at 250 degrees experience more strain empty (cooling system bone dry) than a n* with coolant?

Dont speculate, or you know what? Speculate on the differences in how the engine degrades under this condition with coolant and with out.

Okay, I will explain why.

I had a major leak and I mean major. I had a leaking welsh plug. I ran my engine COOLANT FREE for 2 months 1 mile to work and 1 mile back. At times in traffic, I would cycle 150 and then shut off shortly there after. Like 30 seconds with the temp lite on (funny how I had it timed almost perfectly)

Well thing is I thought the engine block was cracked due to a bad diagnosis and was lookin to replace engine. Low and behold when I had engine pulled for R/R, my mech found the real problem (original diagnosis was from another shop)

So, plug R/R and all is like new.

Back to the original question. Under the DRY conditons of cooling system, what was hurt?

02-26-06, 09:33 PM
So you just drove it a mile, and it hit 250? Did you take it easy on the drive?

The failure mode would be like this... You would have experienced localized hot spots in the head, it's possible you pushed the engine into preignition... Have you pulled the plugs to check for obvious damage? It doesn't blow any blue smoke or run poorly now that it's back together, does it?

02-26-06, 11:08 PM
I think your biggest concern would be head gaskets. Keep an eye on the coolant and temp guage. If you don't use any coolant and the temp holds normal, consider yourself lucky and count your blessings.

02-27-06, 02:05 AM
How hard is it to dump coolant in every day? Even if it blows it all out by the end of the day, so what. Even if it's 20 or 30 $ a day, why risk a $7,000 engine.

By the way, you should know by now 1 mile drives back and forth, off and on, are the worst thing you can do, next to not changing the engine oil for 20k miles. If you've been doing this for years and not ever driving it more, that thing has probably had enough of it.

02-27-06, 09:56 AM
I'd think the localized hot spots would be the biggest concern. Even with the short drive it would be the biggest concern. Now with the drive only being 1 mile...probably didn't wreck anything.

As I've told many people with head gasket problems: How does it run? If it still seems to run good probably nothing is destroyed.

02-27-06, 11:48 AM
Head temps and hot spots. I agree. It could cause gasket failure. I don't really see any likely bottom end damage, if it was really as you say for the distance and temperatures. Remember that the temp sensor is designed to read head metal temp too though, so I'm not sure if you would have hurt it at all... First thing's head gasket though, because it's forming somewhat of an insulator between block and head, likely causing uneven expansion between head and block (any 4100 guys want to join in on this thought?), leading to evenually breaking the head gasket, not blown per se, but broken mechanically. The uneven expansion rates could also cause headbolt thread damage due to expansion/contraction leading to hole out-of-round ness.

02-27-06, 02:10 PM
There is far more stress on the engine running dry than running with coolant in it.

As long as the engine is wetted by coolant, even if it is stagnant and not circulating, the heat input will cause the coolant to boil and that will take a lot of the heat away from the hottest spots and tend to cool the engine. When the engine is dry the heat has nowhere to go and hot spots become a real problem and the thermal gradient thru the parts and across gasketed surfaces is tremendous and puts the parts under tremendous stress.

The good thing going for you is that the Northstar is all aluminum and aluminum conducts heat extremely well. So, hot spots are minimized to some extent by the excellent heat transfer capability of the aluminum. The whole engine becomes extremely hot running without coolant but since it is all aluminum it expands uniformly and damage and stress is minimized. That is one reason the "loss of coolant limp home mode" works so well on the Northstar. All the aluminum in the engine becomes "globally hot" and an engine that is hot all over is under far less stress than one that has localized hot spots that are severe and isolated due to poor heat transfer capability.

The other reason the Northstar is so well protected for loss of coolant is the fact that the coolant sensor (where you are seeing that 150C reading) is strategically located in the cylinder head just opposite the backside of the exhaust port wall in the head casting. This is no accident. It was done for two reasons. It is one of the highest spots inside the engine for coolant so if the engine starts to loose coolant and run dry it will be one of the first things to be dry. Secondly, by being just opposite the exhaust port wall (the hottest spot in the cylinder head) it will read coolant temp when coolant is wetting it and circulating but the instant the passage (and sensor) goes dry it reads the radient heat from the exhaust port wall and very rapidly registers the "overheat" condition. This is different from many engines with the coolant sensor in the block or intake where a loss of coolant will leave the sensor reading erroneous information due to the lack of coolant circulating around it. The Northstar sensor location was developed carefully to act in a dual mode...as coolant temp while coolant is circulating and exhaust port metal temp when/if the coolant is lost.

Soo... running without coolant is not the best thing to do but if you are going to do it the Northstar is the best engine to do it with. It is all aluminum. It has a loss of coolant protection algorithm in the PCM. The loss of coolant protection reacts instantly when the coolant is lost (or the engine is running dry) to any metal overtemp situation and the engine protects itself by cutting out cylinders and pumping air thru the cylinders to cool the engine "internally".

You definitely gave the engine a test by running it dry but I personally wouldn't be worried about anything further happening to it. Once the coolant leak is repaired and the system filled with coolant it should be fine.

02-27-06, 02:44 PM
Aluminum takes 3 times the amount of energy to melt as does steel, it disapates heat well, yet does not "cycle" well. In other words, can't take it as well as some steels and iron. If it were a mile and you babied it, maybe not so bad. I'd be more concerned about the cylinder liners remaining circular and in place, but you may have escaped that one too. Very lucky.
Just a general rule is no coolant no run it.

02-27-06, 02:57 PM
Just a general rule is no coolant no run it.

..unless you're being chased by la chupacabra.

STS 310
02-27-06, 06:58 PM
Bottom line is it runs great.

02-27-06, 07:27 PM
Then it sounds like you escaped unscathed.

If there's ever a next time though, I'd rather run plain water over nothing at all... It's cheap enough to park the hose by the car...

STS 310
02-27-06, 07:40 PM
The thing is the leak was a real gusher. I couldnt get the water in fast enough before it ran out the plug.

02-28-06, 01:31 AM
So are you testing us or something?

Apparently nothing was hurt. You don't have problems do you?

02-28-06, 07:00 PM
Dear STS 310,

You have received a good number of insightful responses filled with wisdom.

I must admit that I seemed to "gasp" when I saw "no coolant" for 2 months. This would have caused my father to have either angst or angina. To him Checking your motor oil or coolant level was a rite of manhood. He was such a vocal proponent that during his funeral the minister intoned "always check your oil"

Yours was a very special set of circumstances and you handled it well.

May I add two (2) tibits about engine cooling? 1. The N* is designed for 7.5 qts oil. No accident, think of all the four Qt cars you have known. N* 's high power, high performance needs coolant protection. I guess that about 30% of N* cooling is perfomed by the oil. Factory design engineer please advise us. Your N* eng was greatly colled by OIL. This fact is not commonly mentioned in forum threads. 2. Top dragster engine patterned in Hemi style. the block does not even have a water coolant jacket. Simply solid aluminum alloy w replaceable steel sleeves.

Most light piston airplanes are air cooled and have 8 qt oil capacity which is supposed to do 40% of the cooling. Strictly 1930's technology.

i am going to check the welch plug . Did you keep the old one? It was rusted
I am sure which leads to the question; why does N*engine have cheap steel whelch plug ? Stainless steel steel would have cost about .35 cents more.

Glad you a got a fix.

STS 310
03-02-06, 08:29 PM
The Whelch plug was replaced with a brass plug I believe.

PLEASE understand one thing. I was under the impression that the block was cracked. From what I have learned, these engines arent the type to mate "upper and lower", so I felt the engine was done anyway. When I had the engine pulled for R/R (I was saving for a rebuilt timeserted engine) the tech found the true problem.

Oh and a request by a "factory design engineer" will most likely not garner a reply.

I was hoping Beazlebob would speak on it.

03-02-06, 08:35 PM
I was hoping Beazlebob would speak on it.
You got the next best thing. ;)

STS 310
03-02-06, 10:02 PM
You got the next best thing. ;)

Absolutley RANGER, sorry for the overlook....

Always glad to hear your input!!!!!!!!!!!

03-02-06, 10:31 PM
No, no, I didn't mean me. :hitstick: I'm not that arogant.

STS 310
03-03-06, 02:30 AM
LOL, but really, following your posts has always been enlightening.


03-03-06, 09:04 AM
No, no, I didn't mean me. :hitstick: I'm not that arogant.

The rest of us knew where you were going...