Sorry about the thread title spelling error. (Moderator's Note - Fixed )

Hello all, I'm looking for some wisdom regarding a project truck that came to me a year ago. It's a '79 F150 4x4 with the 400M and auto trans. I'll describe the history first so please bear with me as it's kinda long...

This truck was severely overheated when the lower radiator hose chafed against the steering center link and split open. The driver said he drove it until it stalled. I acquired it a few days after the overheating and started by pulling the plugs to measure compression. Water shot out of cylinders 6 and 7 while cranking so I pulled the heads and had them rebuilt.

With the heads rebuilt and installed with new Felpro gaskets, new water pump, fan clutch, radiator core, thermostat, new harmonic balancer, complete tuneup, advancer diaphram, carb overhaul and so on, the engine will run up temperature steadily while idling, in as little as 5 minutes. I am using a mechanical gauge that has it's sensing bulb fitted into the thermostat goose neck. I can clearly see when the thermostat opens. When it does open, it opens at about the designed temp of 185*. The temps climb from here until it breaches 220* when I shut it off.

I thought my machine shop failed me and missed a cracked head! I pulled the heads again, this time for replacement. I inspected the cylinder walls, piston tops, everything. I looked for ring marks, scuffing and anything to indicate the overheating damage was beyond the heads. BTW while I was removing the passenger head for the second time, a little water came out of the exhaust manifold bolt over cylinder #3! So I thought I had reasoned correctly.........

Now with the newly installed ATK reman heads, a flow tested 4 row radiator and new gaskets, I am in the same place: The engine overheats while idling after about 5 minutes. I have tried removing the thermostat, to no avail. As a note: the heater is bypassed, and the block pipe fittings are connected to each other via a short hose section.

I am perplexed. Cracked blocks usually manifest with some kind of liquid loss or mixing. I have neither of those symptoms. The oil and water are clean, the engine runs fairly smooth, responds to both timing and fuel mixture adjustments and revs well. Idle vacuum is steady and sufficient at about 16-17 inches of vacuum.

I guess my next step will be to purchase a combustion gas detection kit for whiffing Carbon Dioxide in the coolant. I never liked to use those because of the false positives I'd encounter, but this engine seems to defy repair.

I guess my questions to you are: are overheating episodes the source of cracked blocks, and, do you have other possible ideas to explore that I have not thought of? My current theory (with no backing evidence) is that there is a crack that does not allow water into the cylinder but allows hot combustion gasses to jet into the coolant.

I look forward to hearing your ideas!



Rick

 

I understand it is possible to install the head gaskets backwards, and this would block coolant flow.

 

When you had the heads off did you check the block for warpage? I realize that's kinda far fetched, but we are grasping at straws, so.....

And, have you tried a leak-down test? You might see bubbles in the radiator if you have a leak somewhere.

But I do subscribe to your crack idea. I had something similar on a Windsor that had been overheated, but it would run around town just fine and idle all day long w/o overheating. However, get it up to 45 MPH or more and it would overheat and start belching coolant. It had a blown headgasket that didn't leak until the engine got warm and started working. And it would not show up on a leak-down test, at least not when the engine was cold, and I didn't want to play with the plugs when they were hot. Anyway, yours might show up something with that test.

 

SDDL-UP,

Thank you for mentioning the gasket orientation and I am as positive as I can be that they are installed correctly. When you observe the gaskets, the Felpro gaskets are clearly marked, and they only go on one way without blocking those front coolant ports. And without being argumentative, I presume that if that passage was blocked by the gasket it would cause overheating heating, but not at the rate of temp rise I am experiencing.

Gary,

Thanks for chiming in! I whet-stoned the block decks with WD-40 as a cutting oil to look for any low spots. Both decks looked AOK. BTW, the first heads were sealed well. I learned that as I was pulling it down to replace the heads. So I do not believe gasket sealing is an issue, even though the symptoms suggest otherwise. The coolant gets hot fast.

I am going to purchase a combustion leak tester to sniff the coolant. I live in a remote area so it will be a few weeks until I have results.

In the meantime, if anybody has a pearl to toss this way, let it rip!

Rick

 

Rick - Good luck. Those issues can be frustrating, but when you finally crack it you'll be happy.

 

My guess would be friction between the moving parts is causing the heat, the friction being caused by warping or damage to components someplace caused by the previous overheating.

The water flow of these engines is unique because they don't have a crossover in the manifold. The only thing I remember about the gaskets is they're labelled FRONT in the right places because, as I remember it, some of those passages are supposed to be blocked off by the gaskets (since heads can be installed on either side). Might see if you can find a drawing depicting coolant flow of these engines; I've seen it before but can't remember where....

 

Does your engine actually overheat ? I just went through this with a buddy of mine . He was sure his truck was running hot . He put in a new t'stat . No help . I helped him install a new radiator , no help . Fan clutch , flush , new gauge , water pump , t stat .... I asked him , Does it over heat ? He says .. the gauge reads too high ! I bring my thermal gun home ... His gauge , second one , is almost 20 degrees off ! He is running cool , too cool .

 

one of the things i have ran into is cross firing of cylinder in the distributor. the way to check is cheap and simple. purchase another distributor cap and drill a hole in cap that is easiest to look into while truck is running. You need a timing light and flash rotor as it fire the cylinder. What is happening is a lean condition which overheats the engine. My cure for this was a phaseable rotor, MSD distributor. problem solved. also a vented cap is best on distributor cap. when drilling a hole in distributor cap grind as close to contact as possible. once you flash it with timing light while running you will see the rotor as it lines up with cap and see the spark jump. what you are looking for is rotor lined up. sometimes the rotor is to far ahead or behind rotor contact. As things advance or retard in distrib can change the way it fires and can ignite cylinder before or after the correct cylinder to be fired. if you grind cyliner # 1 and be sure to connect timing light to cyl #1. simple little test. timing chain could be a issue also?

 

Have you tried pulling the thermostat and radiator cap, firing her up, and checking for water/coolant flowing across the radiator?

This almost sounds like no flow through the motor.......

 

need to check the impellar fins clearance to plate. if impellar fins to far away from plate it cavatates internal and fluids just set in pump instead of moving fluids!

 

Thanks, however I find it unfathomable to consider that internal, lubricated parts could rub and generate the heat required to cause boiling temps in the non-contacting water jackets in 5 minutes running, without first seizing.

Thank you, I have measured the temperatures on various metal surfaces using an infra-red non-contact probe and yes, the T-stat goose neck is as hot as the mechanical gauge is registering.

Cheers for some ideas relating to thermal loading. I did not open the timing chain cover after I confirmed there is limited deflection (chain slack) while checking the timing mark against piston TDC. The engine runs acceptable: it accelerates smoothly, no miss-firing, stumbles or rough idle. The tune up components are new, including the advancer. There is no distributor shaft looseness to cause a visible variance while shooting the timing. I have not measured the exhaust gasses, but there is sufficient evidence the fuel mixture is in the ball park. And finally, this thing gets hot fast, while idling. I believe the combustion heat loads expected from ignition or mixture problems would be more gradual.


FB and Wyoming, you guys are causing me to doubt that I have confirmed the flow is correct. I replaced the water pump and installed a thermostat, which I found to be absent upon the first dis-assembly. Now, after starting this struggle, I have removed the thermostat and ran the engine, with zero change in the symptoms. However I cannot recall ever seeing flow on top of the radiator water surface........

What is an accepted test for flow? Some radiators have internal baffles that make the water be fairly still over the tops of the tubes, so I have not relied on a visual inspection down through the radiator cap neck, but that would be easy enough to do!

What I have done is to monitor the thermostat opening and subsequent temp rise rushing through the upper hose and into the radiator. I acknowledge it is not a true measurement, for example: gal/hour. Maybe I have missed something herey??? I'll look into that tomorrow and post up.

Thanks to you all and if you think of anything else, be sure to post up.

Rick

 

I can't imagine that this would do it, but you are aware that the 335 Series takes a different thermostat - right? The proper 'stat has a bell-shaped piece on the bottom that seals the flow off when closed.

Looks like this at Flowkooler:

 

This morning I performed a few different tests to observe the engine and try a few different things to see what is so. I drained out the coolant to perform the following tests and observations.

My first test was to observe flow. I did this by removing the upper hose at the radiator. I blocked off the upper hose neck to be able to fully fill the radiator. I put a slow running garden hose into the cap opening, thus replenishing the radiator with a constant supply of cool, fresh water.

I ran the engine and as expected, the flow out of the upper hose did not commence until the thermostat cracked open at about 160*. The engine did not overheat in this test. It maintained about 170* while idling, and the flow was consistent with a partially opened thermostat. I could have easily measured the GPM, but there are no comparative tables of flow to use as a basis for determination. But there WAS flow once the T-stat DID open.

My next test was to observe cooling system pressurization. To my surprise, the pressure is normal! From a temperature point below the opening of the T-stat, I observed: 180*=5psi, 190*=8psi, 200*= 11psi. I did not observe the pressure above 200* because we know what happens when water boils. I also tested the cap. It is new, but it opens a bit earlier than the cap specification, (spec is 13psi, cap opens at 11psi) so if anything it prevents over pressurization. Given my observations, it appears the pressure cap would open at about 200*, which I assume to be higher than the operating design. However this would serve to protect the engine during hot soak, which I observed to be about 25* over the operating temp when the engine is turned off.

I measured the radiator inlet/outlet temps as follows: 185*/150*, 190*/160*, 195*/176*, 203*/200*. The convergence of these temp measurements indicate to me that the heat build up cannot be dissipated at idle through the radiator/fan exchange.

With the cooling system closed, filled and circulating normally, I sprayed the front of the radiator with a spray of water from the garden hose and was able to lower the engine operating temp from 200* down to 180* after spraying the radiator for a few minutes.

A revision to what I have said earlier: The engine takes about 10 minutes to overheat from cold start, and about 5 minutes from about $140*.

Given the time I spent with this project this morning, I no longer speculate that there are combustion gases being injected into the coolant. I believe that combustion gases would put measurable extra pressure into the system. When I receive the combustion leak tester, I will be surprised to learn there is a combustion leak.

So while waiting for the tool, I must consider all the alternatives: inadequate coolant flow, inadequate heat conduction through the radiator, air pocket(s), ignition timing and/or fuel delivery issues, or???

Rick

 

Gary, I do not have that style T-stat installed. I have the simple, single plane unit from Stant. Do you happen to know the purpose for the double plane operation? Is it for quicker engine quicker warm up of water to the heater core?

Rick

 

Let me look for the answer on the thermostat as that may take a moment. But, I think you have a bad fan clutch that is causing the overheating. A good clutch will engage when the temp gets up and you will know that it has by a roar that isn't easy to miss. When you first start up do you hear much fan noise? Does it increase some time after the thermostat opens? It should.