Radiator boiling after engine shut down (1 Viewer)

[Epic Ed]

Intermittent problem with the radiator boiling. This isn't a case of over heating -- driving around town in bumper to bumper traffic with the AC on my temp gauge stays right in the middle. But about half the time when I shut the engine down, after a couple of minutes the radiator starts boiling. Every time I've heard it, I check the engine temp and it's just fine -- no over heating at all. The problem seems to be happening more frequently, and keep in mind, the radiator is NEVER boiling when I shut the engine off and it never over heats. It just happens after the engine has been shut off for a few minutes.

I'm thinking that I have a hose collapsing some where and it's preventing the coolant from circulating and cooling properly. But the thing that puzzles me is, what hose would collapse when the engine is shut off, but not while it running? I checked the upper radiator hose and it's in good shape and hot to the touch when the boiling occurs.

Any thoughts, suggestions, or input?

Ed

 

[Josh83]

radiator cap.

 

[Epic Ed]

Nope. Replaced it a couple of weeks ago thinking the same thing.

*Important to add -- my AC has also been cutting out intermittently, but I insist that the temp gauge has never moved above the normal 1/2 way marker, so I'm highly doubting it's due to the temp sensor cut off.

After reading a couple of other threads, it's possible that it's the PHH. Any thoughts about this?

Ed

 

[alaskacruiser]

epic- the temp gauge is not very sensitive to temp. changes (large "numb zone" in the middle). If your a/c is cutting out and your coolant is boiling, it is probably no coincidence.

I'd try the folowing:
- Test/replace fan clutch
- Check radiator for flow problems (may be partially clogged)
- Replace thermostat
- Coolant flush

Also wouldn't hurt to replace some of those radiator hoses (and of course the PHH if not already done) while you're at it if you haven't already replaced them. When you say you think it might be the PHH, does this mean you are losing coolant?

 

[alia176]

I believe that the A/C cutoff point is at 226* and the cuton point is 217*. Perhaps you're having overheating issues?

 

[Epic Ed]

Clogged radiator was my second thought so I did a very thorough flush and refill. I refilled with a 70/30 mix of de-ionized water a anti-freeze, topped off with a bottle of WaterWetter. Also did the fan clutch test -- with engine at normal operating temp, I shut off the engine and made sure the fan did lock up and wasn't just free spinning. Haven't replaced the thermostat yet, but that might not hurt.

Sorry for the wild goose chase -- I should have included those details in my OP. But that's the extent of the troubleshooting I've done. I'm not losing any coolant except the one time yesterday when the radiator was boiling rapidly enough that it popped out of the over flow tank. Other than that, none at all, and I don't smell coolant when I run the AC or turn on the heater -- so I'm hoping the heat core can be eliminated as a cause.

From reading through several of the post re: the insensitivity of the temp gauge, it sounds like the consensus is that it won't do much fluctuating in the middle range of temps, but once it gets hot enough to shut off the AC you'll see the temp rise rather rapidly. Also -- the AC has cut out even when the engine was completely cool, like first thing in the morning. So, I'm thinking at this point that I have two seperate issues.

Should I just start replacing hoses? I'm 1/2 tempted to run it down to the stealership down the street and have them diagnose. I can do the replacement if its hoses. Not looking forward to the PHH if it needs to go. I haven't done enough reading yet to find a link to replacing it, but I know it's out there.

Ed

 

[cary]

Should I just start replacing hoses? I'm 1/2 tempted to run it down to the stealership down the street and have them diagnose. I can do the replacement if its hoses. Not looking forward to the PHH if it needs to go. I haven't done enough reading yet to find a link to replacing it, but I know it's out there.

Ed

Hoses don't cause overheating/radiator boiling unless there is a leak. By the time the dealer gets done with "diagnosing" the problem, you would be cheaper off to buy a new Radiator ($300 for a good aftermarket, $420 or so from CDAN), Fan Clutch ($115), and Thermostat ($20) and replace it all yourself (3 hours or so). Without modding the temp gauge to actually work, it is impossible to tell what the likely item is causing the overheating. (i.e. it runs hot on the freeway but not in town, plugged radiator, it runs hot in town but not on the freeway, bad clutch, or it could be a combo of both).

Given you are in AZ where it gets really hot, I would go ahead and replace all three and call the $550 preventative maintence. If you want to start with less, do the fan clutch and thermostat, possibly doing the fluid mod to the clutch to see how that helps. In the end you really need to do the $5 gauge mod to see what is going on.

 

[Epic Ed]

Yeah, I wouldn't mind adding a real temp gauge. How is this done, or can you point me to a link where it's already been thoroughly discussed? Better yet -- I'll search and will mea cupla if I can't find the info.

Ed

 

[cruiserman]

Replace all the hoses while you're doing the head gasket.

 

[Epic Ed]

Oh, sweet jeebus, I not planning on doing a head gasket! The engine is running fine! Heck, I'm not even for certain I have an over heating issue.

Ed

 

[Epic Ed]

Hoses don't cause overheating/radiator boiling unless there is a leak. By the time the dealer gets done with "diagnosing" the problem, you would be cheaper off to buy a new Radiator ($300 for a good aftermarket, $420 or so from CDAN), Fan Clutch ($115), and Thermostat ($20) and replace it all yourself (3 hours or so). Without modding the temp gauge to actually work, it is impossible to tell what the likely item is causing the overheating. (i.e. it runs hot on the freeway but not in town, plugged radiator, it runs hot in town but not on the freeway, bad clutch, or it could be a combo of both).

Given you are in AZ where it gets really hot, I would go ahead and replace all three and call the $550 preventative maintence. If you want to start with less, do the fan clutch and thermostat, possibly doing the fluid mod to the clutch to see how that helps. In the end you really need to do the $5 gauge mod to see what is going on.

Cary -- not a bad idea for just replacing the radiator preventatively. The vehicle has 203,000 on the clock and I know it has been sitting around undriven since at least last November until I bought it a couple of weeks ago. The first thing I did was flush and replace all of my fluids, including the coolant, and the drain was a little rusty at first but I eventually got it to flow all clear before refilling. There could be rust and corrosion causing blockage. But if that's the case, then I'd see some overheating -- and were back to the whole debate about whether it's actually over heating or not.

You're right -- I need the gauge. I've search, but I can't find any info about a cheap $5 gauge as a temp sensor solution. Can you point me in the right direction?

Ed

 

[cary]

https://forum.ih8mud.com/showthread.php?t=64252&highlight=raventai+gauge

I believe the thread also discusses that the same mod works for 93-94, but someone else will have to confirm it.

 

[cary]

BTW, you really do not want to overheat the motor. It appears that many HG failures may be related to overheating the engine unintentionally. At a minimum, check out the threads on modifying the fan clutch and throw a new one in there from CDan to keep the temps down in traffic.

 

[Epic Ed]

Unfortunately, I'm all too familiar with over heating and head gasket failures. I own a 2nd gen 4Runner that has had three engines and multiple head gasket failures due to over heating. I'm paranoid about over heating.

Ed

 

[Rich]

Cary, if the radiator hose on the suction side of the pump collapses, than an overheat will likely result.

Ed, the stock temp gauge needle moves up a very very small amount when the coolant reaches the temp required to shutdown the AC. From what you have described, you are overheating without a doubt.

When you drained the radiator, did you carefully inspect the visible top of the radiator core through the open filler? Use a small flash light, best at night, and look inside the core tubes for clogging.

 

[IdahoDoug]

I think you've got some air trapped in the system, and did you replace the radiator cap with the correct Toyota one, or aftermarket?

The air in the system would allow the heat soak of the shutdown engine to boil the water versus a full system would remain pressurized to resist this. I think you need to top off the system and purge the air. This does not rule out a HG, however. Consider pulling the spark plugs to see if one is different looking.

DougM

 

[Epic Ed]

Thanks for the input on this, guys. Doug, I may be ordering your DVD soon -- I hope I never have to do the head gasket, but the benefits of seeing how to tear everything down seem well worth the price of the DVD and I'd use it for reference to do other repairs.

Tomorrow I'll get the chance to examine hoses, let the engine run without the radiator cap to see if it will burp, and maybe do the fan clutch mod/upgrade. Probably replace the thermostat. If necessary, I'll buy a new radiator next week and I definitely plan on ordering the Greddy temp sensor/gauge.

Thanks again -- I'll post back when I get some results.

Ed

 

[IdahoDoug]

The fact that it's boiling over on shutdown is either a bad rad cap, or air in the system - that simple. All the things you mention in post #17 impact operating temps and won't change the reason it's boiling upon shutdown except infinitesmally. Upon shutdown, the system should be able to handle even a lot of heat without having internal pressure so great it overpowers the radiator cap spring.

It all comes down to this:

-If there's air in there, then the fluid is not under enough pressure and is allowed to boil (which dramatically and suddenly increases pressure and will overpower the best of caps).
-If there's no air in there and it boils, then the cap is the problem. Of course the first time this happens, you have air in the system from then on. So, it's a cycle at that point that won't stop until you purge the air AND get a good cap.

If the air is coming from a leaking head gasket, then of course you have another set of issues. An emission sniffer at any garage can be poked into the overflow tank (if it's not been opened repeatedly beforehand) and confirm the presence of combustion gases, in which case you get to call Cdan.

DougM

 

[Tools R Us]

The fact that it's boiling over on shutdown is either a bad rad cap, or air in the system - that simple. All the things you mention in post #17 impact operating temps and won't change the reason it's boiling upon shutdown except infinitesmally. Upon shutdown, the system should be able to handle even a lot of heat without having internal pressure so great it overpowers the radiator cap spring.

It all comes down to this:

-If there's air in there, then the fluid is not under enough pressure and is allowed to boil (which dramatically and suddenly increases pressure and will overpower the best of caps).
-If there's no air in there and it boils, then the cap is the problem. Of course the first time this happens, you have air in the system from then on. So, it's a cycle at that point that won't stop until you purge the air AND get a good cap.

If the air is coming from a leaking head gasket, then of course you have another set of issues. An emission sniffer at any garage can be poked into the overflow tank (if it's not been opened repeatedly beforehand) and confirm the presence of combustion gases, in which case you get to call Cdan.

DougM

I think you nailed it, Ed was told that they just replaced the cap before he bought it, but it is a crusty original looking stocker. The radiator looks like it was just replaced or serviced, all hoses are new, new clean green coolant, new aftermarket very beefy fan clutch, but all of the foam seals around the radiator and the lower sheet metal tray are missing. I didn't see any signs of a bad headgasket.

Hopefully a new cap will solve the air in the system problem and replacing the airflow seals and plate will fix the low speed heating and A/C issues.

Good to meet you Ed!

 

[cary]

I think you nailed it, Ed was told that they just replaced the cap before he bought it, but it is a crusty original looking stocker. The radiator looks like it was just replaced or serviced, all hoses are new, new clean green coolant, new aftermarket very beefy fan clutch, but all of the foam seals around the radiator and the lower sheet metal tray are missing. I didn't see any signs of a bad headgasket.

Hopefully a new cap will solve the air in the system problem and replacing the airflow seals and plate will fix the low speed heating and A/C issues.

Good to meet you Ed!

Glad to see he went to you rather than the dealer, I'm sure he paid far less and received far better advice.