Temperature gauge pegged...

[Jim Saraceno]

I thought I had ironed out all the issues of the cooling system. Last weekend, a friend of mine asked me to chauffeur his son's bride to be and her dad to the wedding to make a grand entrance. The temps that day were hovering around 102-104!

I had to drive around 10 miles on the highway and by the time I got off the highway, the temperature gauge was pegged!

Luckily, the car kept running just fine and I managed to get the bride and father delivered as planned but I was very concerned.

Two questions... 1. Should our cars be able to run at these temperatures without over heating?

2. If a car over heats, what can happen and are there signs to heed before something bad happens?

BTW... for anyone wanting to review all that I have done to overcome previous overheating problems, here is the link to that thread... http://www430.pair.com/p15d24/mopar_forum/showthread.php?t=26054

Edited September 11, 2011 by Jim Saraceno

[55 Fargo]

Jim, your t/stat, is it suspect, maybe stuck closed, or not opening very much.

The water pump impellor, could it have been not mving toopump coolant.

The rad is okay, isn't it?

Higway speed should get things heated up, but only 10 miles, I can see running at 190 -200, but not pegging the gauge.

Did you rad boil right over?

Once the engine is super hot over 200, so oes ths oil, and $hit happens, crack blocks/heads, fry things.

I wold suspect, the t/stat, timing, or water pump, if your rad, and engine coolant passages are clean and in good condition.

An extemely lean fuel mixture could cause this also, at least I have seen that happen on some of my small engines.

102 and things can go south ina hurry I suppose.

Let us know your speed, and all of what happened, that way maybe someone can help you sort this out. Also not that this would necessarily cause the engine to overheat, but does your heat riser work as it is supposed too....

[Jim Saraceno]

I've been through the entire system. The radiator passed the flow test, the thermostat was replaced last winter, the engine was rebuilt a few years ago and the block hot-tanked so I have to assume all the passages are open. The water pump was replace about 8 years ago. I'm not sure how you would tell if the impeller was not up to snuff. The heat riser works just as it should.

I was driving around 50 mph (no overdrive and a 4.125 rear end). I never saw any sign of boil over. I'm not sure at what temperature coolant will boil at a 50/50 mixture.

She is fine if the temps are in the 80s or below. Quite honestly, I never drive her when the temps start to hit the 90s so I'm not sure at what outside temp it starts to be a problem. I would have never taken her out in those temperatures but I had promised the bride and groom.

[Barabbas]

I know that this is simplistic but have you checked the guage?

[Jim Saraceno]

I know that this is simplistic but have you checked the guage?

Reply With Quote

Yes.

[Joe Flanagan]

I don't remember if this was discussed in the previous thread but were the water jackets checked for rust scale (as in popping out the welch plugs)? I believe I heard here that hot tanking an engine won't necessarily get all that out.

[Don Coatney]

From a thread I posted to earlier this year.

Just checked into the hotel in Warner Robbins, Ga. Merle Coggins is also staying here. I just checked my GPS odometer and so far on this trip I have clocked 400 miles even.

I got stuck in a gridlock near Macon Bacon, Georgia on the way to Tims this morning. Parked in this gridlock for over a half hour. It is normal for my car to gain a lot of engine temperature when I have been driving at freeway speed for an extended period of time and suddenly drop the speed to zero. Also normal for my electric fan to kick on and drop that temperature after a few moments. However in this case I went from freeway speed to zero in a plymosecond. Fan kicked on but temperature continued to slowely climb as there was no wind other than that produced by the electric fan. No place to go, no way to pull off to the shoulder as there was traffic all around me, so I sat there and watched my temperature gauge climb to around 230F. I used the throttle cable to drive the idle speed up to around 1200RPM in order to circulate more coolant but this did not help much. Never boiled over. After an eternity got clear of the gridlock and back up to speed. Temperature dropped to 180 in less than a mile and my thermostatically controlled fan dropped off. Engine continues to run great so I dont think any damage was done.

Plans for tomorrow are the return trip home. If I make any detours my trip home will be about another 400 miles.

[greg g]

Well water boils at 212, and I beleive that is pegged on our cars temp gauge, however 50/50 coolant by virtue of the mixture increases the boiling temp to 250/260 degrees. So while the gauge is pegged at 212 or a bit higher, the actual coolant temp is still below it Boilig point. The problem with boiling is not so much the temperature itself, but rather the break down of liquid to vapor, as vapor has no heat absorbtion or colling properties. So when the bubbles begin to form is when the problems begin within hthe engine. but 260 degrees is still a long way form melting points of metal in the engine.

Usually the head gaskets fails, and get you to shut down the engine. If stuff starts to boil the heating and cooling become uneven leading to twisting ans warping.

The old rule of thumb as it relates to cooling systems is that if overheating occurs at idle or low road speeds, the problem is likely related to air flow, if it occurs at highway speeds it usually means there is a coolant circulation problem, or a problem with coolant contacting the heat producing surfaces, keeping the coolant from properly absorbing heat from its sources.

[wallytoo]

not familiar with the cars. do they have a pressure cooling system? or are they open? pressure serves to increase the temperature at which a liquid will boil, so if the cars have pressurized systems, the boiling point of just water would be higher than 212.

[ptwothree]

Jim....According to your #48 post, you found a problem with the t-stat and that was it. Now the hot weather is back and so is the overheating problem.

Did you ever get an inferred heat gun and try to diagnose with it?

Wish we had these back in the day. Even on a not so hot day, idling on the driveway, you can detect hot spots in the cooling system and even tune a dual carb set-up by checking the heat at the exhaust ports.

Anyways, try it and let us know if you turned up something.......

[Jim Saraceno]

I don't remember if this was discussed in the previous thread but were the water jackets checked for rust scale (as in popping out the welch plugs)? I believe I heard here that hot tanking an engine won't necessarily get all that out.

Yes, the freeze plugs were all pulled before it was hot tanked.

Did you ever get an inferred heat gun and try to diagnose with it?

Yes, there are not hot spots that I can find.

I guess I'm going to have to take her out on other hot days and try to get a handle on just which air temps I start to have problems. As I said, there are no problems in the 70's to mid 80's and I usually never drive it when it get much hotter.

[55 Fargo]

Yes, the freeze plugs were all pulled before it was hot tanked.

Yes, there are not hot spots that I can find.

I guess I'm going to have to take her out on other hot days and try to get a handle on just which air temps I start to have problems. As I said, there are no problems in the 70's to mid 80's and I usually never drive it when it get much hotter.

Check to see if the t/stat is functioning correctly, is it releasing coolant to the rad, is your lower rad hose collapsing any, when the engine rpms go up, thus reducing flow.

I would think that temps of a super muggy dead air 102 f, would reek havoc, but would still asume the engine temp should not get so hot, at very moderate speeds for only 10 miles or so.

Could you have a head gasket leaking hot exhaust gas into the coolant, resulting in an elevated engine temp.

You know Jim, I drove my car one super hot day of about 95f, 12 miles to a car show, temp did not rise over 170. I am sure that if I were driven 50 miles or through the city, it may have risen another 20 degrees, but that's about it.

Are you 100% sure you have good flow in your rad, restrictions to coolant flow and poor heat transfer, would show up on bvery hot days if that be the case, or any other thing that would not allow air to move through the rad, as the fan does not do all that much at highway speeds...

[woodie49]

I recently drove the Woodie in about 95 degree weather and went inland a bit, so I assume it was close to 100. The motor temp seemed to stay around 200, maybe just a little over. I assume that if I had idled for any length of time, it would have gone hotter, but there was not any significant traffic and I kept her below 60. It seems odd that your motor would overheat while running at speed given all you have done to it. I would actually remove the thermostat and see if it helps, I don't think it could hurt much and it might help narrow down the issue.

I just got an infrared temp gun and it verifies the dash gauge. Also noted a couple other things: for me, the back of the engine at the head, where the by pass comes out is about the hottest area, maybe 10-20 degrees hotter than the T-stat housing (which sat at about 165 with a 160 degree thermostat) and the water pump. My heater is all properly plumbed and it was off with the slide levers to the left, so i do not think there is water flowing through at that setting (?). The area where the temp guage sensor is located in also about in the hottest section. The radiator was also pretty close to the temp of the T-stat. I verified that by using a thermometer in the radiator, so I feel like the infrared is accurate (besides, I had to play with it).

One thing I noticed when running in really hot temperature is that it was the only time that I saw my oil pressure go below 40 while running. It was fine at speed, but at idle it went down to what I think would be about 25 lbs. I haven't seen that since. I run straight 30, maybe I should run 10-40.

Usually the first thing to go of consequence during overheating is the head gasket. If this went, I would also have the head checked to see if it required milling to true it up.