UKrunner

Hi folks, I replaced the head gaskets on my '98 3.4 with 190K and it ran fine for 11K miles. Recently its started to gradually overheat with a higher speed. Reduce the speed and the temp goes down. I am wondering if a head gasket failed again. When the engine is cold and I first start it, it will push coolant out of the radiator if the cap is off. I cant remember if this is normal or if it should only rise as it gets hot? I did have a small heater hose leak which may have let air get in and there may be a bubble in the system. I have tried to burp it but it still pushes coolant out when its cold.

I have no other signs of head gasket failure. Plugs are dry and clean, no steam in the exhaust, typical power and economy, no bubbles coming out of the radiator. It doesnt seem to get pressurized enough to get past the cap and into the expansion tank - unless it over heats. When I replaced the gaskets, I completely rebuilt the engine and had the heads and block resurfaced.

Any help and ideas would be great. I really dont want to get in to replacing heads gaskets again if I dont have to.

wyoming9

iTrader: (1)

Bad radiator cap??

Not allowing things to work like they should.

Funny that it overheats with more airflow coming through the radiator how is the radiator itself ??

Bad hose or hoses sucking closed ?? Where they replaced when the engine was done??

Fan clutch working like it should??

It worked good for 11K what happened??

Electrical gauge problem??

It is possible to have a head gasket fail into the coolant passage only till it gets worse.

Pressure test the cooling system for piece of mind.

UKrunner

I'm getting a new cap this morning but I don't think that's the issue. It has a new radiator, pump, hoses and thermostat.

I'd really like someone to take the cap off their radiator on a cold engine, start it up and see if coolant rises out of the radiator almost right away. If it does, mine is doing the same and I'm guessing everything is ok. If it doesn't, I'm guessing I have a head gasket blown or an air lock from when I replaced a heater hose. Those are the only 2 things I can think of that would cause this cold engine pressurization of the cooling system.

I may take out the thermostat to rule that out too.

fierohink

You can get a test kit at most auto parts stores to test for combustion by-products in the coolant.

You could also try securing the cap until the thermostat opens and then seeing if you are still pushing coolant.

Do you remember how you phased the jingle valve?

UKrunner

I do have an exhaust gas checker which I'll try later.

I did notice that the only areas of the radiator that are hot are right behind the shroud. The complete area in front of the fan is cold. I dont mean luke warm, I mean stone cold. Is this normal or could there be a blockage? I had previously ruled out the radiator because it was replaced when the head gaskets where done.

fierohink

Anything is possible I suppose. Can you pull the t-stat and run it to see if it is just a stuck closed stat? Or disconnect the rad and run a hose through it to check for blockage?
There are a lot of passages in rad, I think blockage would be low on my list with a relatively new rad.

UKrunner

Gas sniffer stays blue. I agree with you on the radiator but, it really does stay hot on one edge and cold everywhere else. The difference is dramatic. I was under the impression that the radiator should be a uniform temperature give or take over the entire core area, getting cooler towards the bottom. In the middle at the top, 4 inches below the cap, its stone cold.

fierohink

Well if your thermostat isn't opening, the coolant doesn't have any place to go. It isn't circulating yet.

DHWRIGHT

my 22re runs higher temp on highway then in the woods because I have my thermostat removed. the reason for this I guess is when at higher rpm and no thermostat the coolant does not stay in radiator long enough to cool down before going back to engine, even with the thermostat open it still slows the flow just by being in the way. Also I have seen radiators on motorcycles at work cold to touch if they are not bleed correctly. Air wont conduct heat like water. Coolant should come out of radiator when you 1st start engine cold if its full and you have a thermostat because the water pump pushes all the water between thermostat and pump back to radiator, but with thermostat closed the extra coolant in engine being put back in radiator cant go back to engine. Water follows path of lease resistance, if the cap was on then it would go to coolant reservoir. like fierohinko said about passages in radiator, I seen a cutaway of a radiator when I attended MMI and that's very unlikely.

skypilot

iTrader: (1)

I got a bucket of bad thermostats, new. T-stat's can be hit or miss if they are any good at all. Simple device, you think they were hard to make.

UKrunner

Before I go out and buy a new radiator, is anyone willing to run their engine till its warm then turn off and check to see if the radiator is hot behind the fan shroud but cold in front of the fan? If yours is cold where the fan blows it's the same as mine and I'll not replace it.

Thanks.

skypilot

iTrader: (1)

Have you opened the cap and looked in? Is frosty with carbonates? You could take it to a radiator shop and have it boiled out, which is cheaper. Mine rot away from salt before they plug up. I'm assuming yours is not moth eaten? Have you taken the cap off and see if you get any flow at all across the top? Have you parked the truck pointing uphill to "burp" the system?


There are radiator flush products available that sometimes work pretty good. At least if you do try a flush and it gets better then the radiator does need a boil job.

UKrunner

Looks clean inside. There is flow across the top to the right when you look at the front of the vehicle.

fierohink

And just to clarify, you ran for 11k miles without any problems? You heat up on the highway under load, but not around town? Will it heat up if you are parked and idling?

wyoming9

iTrader: (1)

Are you by chance feeling the condenser instead of the radiator??

My whole radiator is warm after a 5 mile drive but the condenser is cool to the touch.

But then I run a three row Copper Brass radiator in both my 3.4 engines.

As of late Stant caps and thermostats made in China are hit and Miss for quality.

UKrunner

It appears to be fixed. I put in a new radiator and thermostat and am now sitting between 179 and 190 depending on load and speed. Its also no where near as pressurized as it was and I can run it with the cap off. The radiator is hot all over so it seems I had a blockage in the old one. I put back in almost a gallon more coolant than came out. Thats a lot! I had burped it so many times and never got any bubbles out so I can only assume that almost the entire radiator was blocked and empty of coolant.

wyoming9

iTrader: (1)

Glad you got it sorted out .

Now what caused the last radiator to get blocked???

So you don`t have a repeat of this adventure.

UKrunner

No idea. The engine was rebuilt, heaters flushed, new hoses, new radiator, pump and coolant all at the same time. Coolant looked clean when removed. All I can think of is some milkshake was still in the heater cores that didn't come out when I flushed them and took 11000 miles to relocate to the radiator.