1994 3.4L running hot - Team Camaro Tech
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post #1 of 10 (permalink) Old Aug 15th, 10, 04:25 PM Thread Starter
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1994 3.4L running hot

Hello guys... first time poster... I'll try to be brief.

I bought a 94 with a blown head gasket (No, I didn’t know it at the time ). The guy that sold me the car (out of state… yeah, I should have known) had used some rusty looking redish brown crap to seal the leak so he could dump the car . After a month or two the overheating started, I did all the standard stuff, I flushed the system, replaced the thermostat, radiator cap and hoses. Then I discovered the blown head gasket (bubbles in the radiator fill). Leak down test verified the HG is blown at number 5.

I used a few bottles of Steel Seal just to tide me over till I could get time to replace the gaskets and wadaya know... the stuff worked. No more overheating... no more fluid loss... engine runs fine but just too hot. It runs at about 235 to 240 (verified with a thermo-couple) but doesn't boil over. I removed the thermostat and took a test drive at Highway speeds on a nice cool 68-degree morning. No difference... 235 to 240 degrees. I figure if the cooling system can't handle a highway drive on a cool morning then something isn't working right. Hoses are all new... radiator cap is new... I even had the radiator out and ran water thru it but that only means that water can get thru it... it could have half the tubes blocked without me knowing it. Also... when I had the radiator out I took the time to remove all the road gunk stuck in the fins. It's all perfectly clear now.

I'm leaning towards replacing the radiator. Yes? No? I'm crazy? Or should I just do the head gasket and worry about the running hot issue later? Any advice you can give would be most appreciated.

Oh… I almost forgot… the fan never comes on unless I turn on the A/C. For all I know, that was the original reason the head gasket blew to begin with.
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post #2 of 10 (permalink) Old Aug 15th, 10, 09:48 PM
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Re: 1994 3.4L running hot

Well I would fix the fan and head gasket, you might be wasting money on a radiator.

And flush that leak fix crap out as soon as possible, you or the previous owner may have clogged something...
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post #3 of 10 (permalink) Old Aug 16th, 10, 03:26 AM
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Re: 1994 3.4L running hot

Only problem with stop leak products, they plug everything - heater core, radiator, hose connections - kindda like plague in the arteries, one bit stops and attaches to the wall, then another, then another two, so on.

You might use a Prestone Flush before tearing apart the engine to remove as much stop leak you can. Block drain plugs also. Flush as best as you can.

ECM controls the condensor fan, pass side, via A/C switch. Temperature sensor controls drvr side fan through ECM and fan relay, fuse/fusible link?

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post #4 of 10 (permalink) Old Aug 16th, 10, 06:35 AM Thread Starter
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Re: 1994 3.4L running hot

Quote:
Originally Posted by 400bird View Post
Well I would fix the fan and head gasket, you might be wasting money on a radiator.

And flush that leak fix crap out as soon as possible, you or the previous owner may have clogged something...
Thanks for your reply... I greatly appreciate your input.

I already flushed the leak fix crap out.

I have a follow-up question... At 60 mph on the highway the fan is irrelevant, there is many more times the airflow from the forward motion of the car than the fan could ever produce, but the car was still running hot at that speed and without a thermostat.

I would have thought that even given the other considerations (blown head gasket temporarily sealed with Steel Seal) that the radiator should have been able to bring the water temperature way down... at least below the normal operating temperature of 200 to 210. This is what has caused me to suspect that the radiator isn’t performing up to spec and may be clogged.

I agree totally that the only acceptable repair of a blown head gasket is to replace the gasket but I would like to determine if I also need to replace the radiator.
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post #5 of 10 (permalink) Old Aug 16th, 10, 06:55 AM Thread Starter
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Re: 1994 3.4L running hot

Quote:
Originally Posted by Everett#2390 View Post
ECM controls the condensor fan, pass side, via A/C switch. Temperature sensor controls drvr side fan through ECM and fan relay, fuse/fusible link?
Thanks Everett but I may be misunderstanding what you mean. It sounds like you are saying there are two fans... one controlled by A/C considerations and one controlled by temp sensor. My 94 has a single large fan.

Also… I have no desire to endorse or defend any products but this company insists that their product cannot cause blockage in the cooling system because it contains no solids. Something about chemical reactions between the product and the glycol based anti-freeze activated by extreme heat (much higher than can be found in the cooling system). Maybe it’s true and maybe it’s not… I have no idea… but the product was perfectly clear when I used it (I could see thru it) and the leak did stop. Maybe it will start again in a month; I don’t really know… if I had the answers my car would be running cooler and I wouldn’t be asking all these dumb questions.
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post #6 of 10 (permalink) Old Aug 16th, 10, 09:07 AM
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Re: 1994 3.4L running hot

I was thinking of 3rd Gen, they have two fans. Yes, technology of stop leak detector may have came a long way.

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post #7 of 10 (permalink) Old Aug 16th, 10, 02:12 PM Thread Starter
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Re: 1994 3.4L running hot

A quick follow-up:

I ran a test with the engine idling and thermo-couple sensors connected to the water inlet and outlet of the radiator. The fan finally did come on when the water hit 245 degrees on the instrument panel gauge (I guess I just never waited long enough) and according to the thermo-couples (not the instrument panel gauge) the water temperature dropped dramatically when the fan came on.

I can't be 100% certain as to the exact water temp values because there may be air in the upper radiator hose which is preventing accurate measurements but even taking that into consideration, the differential in water temp between when the fan turns on and then off was over 35 degrees. If my measurements are accurate, the fan came on when the return water temp hit 196 degrees and shut off when it hit 160. I'm no expert but those numbers look pretty good to me. I'm using the return numbers rather than the supply numbers (cool side of the radiator instead of the hot side) because I wanted to verify that the radiator was taking the heat out of the water... and clearly it is.

Oddly enough... the temp gauge on the instrument panel never moved off the 240-245 degree reading. I guess that could mean that the water isn't circulating throughout the block where the sensor is or the gauge or sensor is faulty. There is no sign of overheating… not even a whiff of radiator smell… the kind you get when coolant escapes.

I have read comments from many people who say to be very careful about air trapped in the cooling system of the 3.4-liter engine… that there are no bleeders anyplace in the system but several places where air can accumulate and restrict flow. Do any of you know this to be a fact and if so, what is the proper procedure for removing the air?

Thanks again… your input helps more than you realize.
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post #8 of 10 (permalink) Old Aug 16th, 10, 05:56 PM
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Re: 1994 3.4L running hot

Seems your science project turned out some good results.

On coolant level, when cold, remove the rad cap and add coolant every day until the level tops out. Also, keeping the reservior full or at the max level and several heat/cool cycles will displace air with coolant during cool down, coolant contracts and engine also, and draws coolant back from reservior. Coolant system heats up, pushes out air, and displace with coolant when cools. A vicious cycle. Keep a mental check or mark with tape and date it when coolant was added to keep track of coolant used. At some point in time, it should "level" out.

A quick backyard calibration of the coolant temp gauge would feel the upper hose and when it gets hot, thermostat opens up to allow flow, check gauge. If you have a 160° thermostat installed, then the point on the gauge is 160° - mental check.

Fan may be controlled by either the PCM, receiving the coolant temp through its two-wire sensor, usually mounted by the thermostat housing, or a separate single wire thermal switch in the cylinder head opposite head of the gauge sending unit. If thermal switch controlled, you might be able to wire in a manual toggle/rocker switch with the same wire and manually turn on the fan leaving the thermal switch in place as to not interrupt the OE design circuit.

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post #9 of 10 (permalink) Old Aug 16th, 10, 06:36 PM Thread Starter
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Re: 1994 3.4L running hot

ROFL! Science project. That gave me a good laugh... especially because it's so true. I guess I am turning this thing into a bit of a science project.

Yesterday I ordered the shop manuals for my car and as soon as they get here I'll pour over every detail before I start tearing the engine down. I almost can't wait to get started because as you may have suspected... I love this stuff. The reason I'm being so meticulous up front is because I know that I will never be satisfied with just pulling the heads and changing gaskets. I'll almost certainly do a valve job and I can't imagine myself putting this engine back together with the old water pump... why would I do that? And of course the serpentine belt has got to be replaced and who could resist checking those injectors when they are so tantalizingly within reach during teardown? Oh what the hell… the water temp sensors are history as well. Did someone mention an aluminum radiator?

BTw, I sent an email to the company that makes Steel Seal telling them about my car and they responded with an email containing a phone number and a name and told me to call them that they’d like to talk to me. Maybe it’s voodoo but it’s voodoo that doesn’t hide and wants to help. I’ll be very interested to see whatever residue their product left in the blown gasket area when I pull the heads. I’ll post some pictures when I get them off.
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post #10 of 10 (permalink) Old Aug 29th, 10, 10:29 AM Thread Starter
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Re: 1994 3.4L running hot

I'm not sure I should post this question in this section but this is where the discussion started so I guess it will be all right. If I need to move to a different board please let me know.

I'm in the middle of the teardown and I noticed a peculiar situation... the area where the head meets the lower intake manifold and forms the surface for the rocker cover gasket to seal against, doesn't line up exactly... the surface of the lower intake manifold is a good 1/16 of an inch lower than the same surface on the head. I included a picture with a red arrow pointing to the spot on the head that should meet the lower intake manifold (sorry, but the lower intake manifold was already removed before I took the picture).

Does anybody know if this is the way it is supposed to be or do I have the wrong intake manifold on this engine or perhaps the wrong heads? I read someplace where they said that there are two versions of heads for the 3.4L engine, early version and later version with the primary difference being the size of the intake ports, but both versions of the heads will bolt to the block.

Thanks for your help.

Rocker Cover Gasket
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