Tough overheating problem

[gone huntin]

A friend asked me to help him figure out his overheating issue in his buggy. It's Jeep bodied with GM drivetrain (350 stock). He went over the summer to help out a guy that was stuck in a local lake bed and the fan switch accidentally got turned off and the engine ran pretty hot. Ever since then it runs up to about 245* while he's crawling around, but if he stops, it stays where it's at, doesn't go up or down. If you start it cold and just let it idle it will climb to 210*, then fall back to 180*(t-stat temp) and then climb back to 220* and stay there until you rev it up, then it jumps to 245*. The heads have been off and checked for cracks and warpage, none was found. I even used a tester that goes in the radiator and uses the blue fluid to check for combustion gasses in the coolant, none found. It has been tried with no t-stat, a gutted t-stat, a 180* t-stat and a 195* t-stat all with the same results. We tried different temp gauges, same rusults. It has an all aluminum radiator made for the V8 swap and it has it's third new waterpump since this started. I've checked the timing, even unplugged the advance with the same results. If it matters, he's running on propane.
Guys, I would appreciate any ideas that you might have on this.

 

[toomany]

Are you sure all the air is out of the system? Correct water pump (v-belt or serpentine)? What about the radiator cap?

I'm assuming it's not loosing coolant anywhere. Does the overfloor rise and fall like it should?

I'm not familiar with propane setups, but uneven fueling could cause hot spots. As could running lean.

 

[gone huntin]

Are you sure all the air is out of the system?
Yes, I have one of those funnels with a radiator cap made onto it for that purpose. It has no heater core to trap any either.

Correct water pump (v-belt or serpentine)?
Yeah, that's why there have been three on there, the first one was for serpentine. He didn't know they were reverse rotation.

What about the radiator cap? New

I'm assuming it's not loosing coolant anywhere. Does the overfloor rise and fall like it should? Not loosing any coolant until it erupts like old faithful.
No overflow jug, just vented out and down.

I'm not familiar with propane setups, but uneven fueling could cause hot spots. As could running lean.

Thanks for the reply.

 

[4X4HIGH]

Make sure it has the CORRECT radiator cap. The caps are different between a recovery system versus a non-recovery system. Also make sure it is a 16lb cap.

 

[gone huntin]

It's got one of those caps with the spring loaded handle on it to relieve the pressure. I don't recall what the pressure rating is. I'm still not convinced it doesn't have a head issue since it erupts right after revving it up with the funnel on it.

 

[Jessie James]

Have you done a compression/leakdown test? You may have warped the head and are leaking through the head gasket.

Another easy test is to check for coolant in the oil, and vice versa.

Another guy on the board had a similar problem, and had installed his thermostat upside down. Simple to check, easy to overlook?

 

[gone huntin]

Well, the heads were removed and checked for straightness and cracks, came back OK. There is no cross contamination of the fluids, and the thermostat is in correctly.

 

[Jessie James]

Doh, you said that, sorry.

How old are the radiator hoses? I've heard of them collapsing while driving if they are old & worn out, but I think that was more of an issue in the 70's and 80's. I would also assume you have newer hoses and/or they have the metal coil inserts to prevent them from collapsing.

However, if they are old, or seem really soft and easy to crush with your fingers, or maybe the wrong size, perhaps it's time to replace them?

 

[4X4HIGH]

It's got one of those caps with the spring loaded handle on it to relieve the pressure. I don't recall what the pressure rating is. I'm still not convinced it doesn't have a head issue since it erupts right after revving it up with the funnel on it.

There are still two types of radiator caps regardless of whether it has a pressure relief or not.

 

[Fordum]

When you do the gradual warm-up thingy, and then rev it up, how long do you have to rev it to get the bad stuff to happen. In other words, a quick blip or let it go for a while.

Heres the deal. If you get a big eruption out of the radiator, then you almost have to have gas of some kind in the cooling system. Assuming that you got all the air out to start with, that means a gas of some kind is getting in when you rev it.
There is only three ways I know of that can happen.

One: combustion gases from the cylinders through a cracked block, head gasket, or head.
This would happen fairly quickly when you rev it.

Two: Steam from boiled coolant due to stopped coolant flow.
That should take a few seconds even if the water pump stopped entirely.
Or Three: Air from outside.
I have actually seen this once. A friend's radiator hose had failed internally, and when he revved the engine it would suck flat inside. The water pump sucked air in around the shaft seal. Never leaked water either.
In your case, I suspect that the gas is either steam from the coolant, or combustion gases.

Here is a thought.
I have used the blue stuff many times to find combustion gases in the coolant. However, I never considered what it was detecting. It was always just combustion gas.
Does an engine running on Propane produce the right gas for that stuff to detect? I have no idea. If there is any radiator guys here or close to you, you might ask.

Given your symptoms, I suspect that the water pump is ceasing to pump at high rpms. This could be caused by it getting air logged from sucking air, a loose impeller on the shaft, I have seen that at least 4 times, or the wrong impeller for the housing. I have seen that once, and suspected it a second time.
The one time I know it happened, I took the water pump back to the store it had just been purchased from. When the counter guy brought out another one, it was extremely obvious that the impeller was different. From what we figured out the rebuilder just put the wrong impeller on. Since we could not find another one like it.
I would do whatever I could to check for any blockages.
In the radiator or hoses, and I would take the water pump off and try to turn the impeller on the shaft. Just because its new is no guarantee it is good.

 

[Jessie James]

... or the wrong impeller for the housing.

That reminds me - I have seen this once before. I replaced the water pump on an old car and the new one had bent metal arms for the water pump like this:

I thought nothing of it and put it in. It promptly overheated like crazy.

I got another pump and it had a nicely cast impeller which fit perfectly formed into the housing like this:

That one worked fine and my problems were solved.

Hope that helps.

 

[Fordum]

Thats funny. The pump that would not work on the car I was working on had a tapered cast iron finned cone, and the correct one was the bent metal one like your wrong one<G>.
It all depends on the housing.

 

[gone huntin]

Well, it does act like one that has an air pocket in it, but it's been bled and bled and bled and we don't get any air until the rpm is raised up then the temp starts climbing and then it spews out the coolant while the funnel is on it. It doesn't do it if you rap it, just if it's held steady or driving. It takes about ten to fifteen minutes to start climbing up if you start driving it cold. I never thought about the propane not creating the type of combustion gases that will show up with the tester. There is no fluid cross contamination.

 

[Apocalypse]

This might be a silly question. Are you using a late model pulley setup? some of thos were reverse rotation and will cause all sorts of weird problems until you get the correct water pump. Just thought i would throw that out there for consideration.

 

[4X4HIGH]

This might be a silly question. Are you using a late model pulley setup? some of thos were reverse rotation and will cause all sorts of weird problems until you get the correct water pump. Just thought i would throw that out there for consideration.

That has already been addressed.

 

[Fordum]

I did some heavy duty browsing, and while I found lots of places you can buy the radiator combustion gas testers, plus replacement fluid, nowhere did I find a place that address whether or not it will work with propane. I found one place that said it would work with gasoline or diesel engines. Well, we are dealing with a gasoline engine, but its not burning gasoline, so who knows.
My best guess right now, is either something wrong with the water pump, or a crack in the cooling jacket of the engine somewhere.
If that detector does not work with propane, then I think it most likely a crack somewhere. Otherwise, I would pull the water pump, grab the impeller in one hand, the drive hub in the other and twist in opposite way as hard as I could. Its very possible that the hub or impeller is slipping on the shaft when it gets hot.
If so, it probably will not slip in your hand, but if you look at where the shaft goes through the hub and impeller, you may see where it has been slipping.

J.

 

[496truck]

This is interesting, as I have a 93 C1500 P/U 350 TBI half torn apart trying to diag a very similar situation. Runs and idles great, drive it for a bit and it overheats. New rad, t-stat, hoses. W/P is recent but I have pulled it and took the cover off to check it anyways. Gonna look more closely when I get home tonight. My father in law (his truck, longtime mechanic/machinist) was convinced it's head gaskets, but I have been doubtful. None of the telltale head gasket issues are present.

 

[Jessie James]

Well, going back to my first thought, I had a car which overheated several times, and each time I had to resurface the heads and put in a new head gasket. As soon as the head warped again, it was time to re-do it. And they all did the same thing.

Did you check to be sure the block was flat, too?

If so, then maybe use some of that super copper head gasket stuff? I forget what it is, but basically it seals super well.

 

[gone huntin]

I wasn't there when the heads were off, him and another friend did that. I got called over to adjust the valves after they bolted the heads back on. I was there when the intake went on though and made sure the gaskets were oriented correctly so the front ports weren't blocked. The first time he drove it after it went back together it ran for almost thirty minutes with him cruisin' around. Then he went out back to our trails and started playin' on some hills and then the temp started going up. It went to 245* before he shut it off. He did say that he dropped off into the creek and splashed some water on the radiator and the temp dropped quickly then. (Just heard about that today) This is looking more like a stopped up radiator to me.

 

[35dp]

Ive been around circle track racing for a few years, my buddys wont use those aluminum aftermarket rads after they have been overheated, they say they wont run as cool ever again.