Hello all. It's been squite some time since I've posted but I visit this site daily throughout the week when downtime allows at work. Here's an apology up front about the length and whineing that is to follow. Last September the old 2.8 started choking on a bad rod bearing. For the past couple of years I've been thinking of the 3.4 swap and thought this the perfect opportunity. Anyway found a shop, found the engine (salvage with 60K supposed miles), gathered all needed parts and delivered it all. Now I could go on about how pathetic these guys turned out to be, but that's not important. Got the truck back Friday. The thermostat was locked so they punched it out (you know, since I wasn't there to buy one for them). Without doing that they couldn't let the engine run. My patience had worn about as thin as my hair so I decided to take it and work through all the bugs myself (actually get it to my hometown to people I trust - couple hundred miles away). So from the shop to my place (30 miles) that sumbitch got hotter than I have ever seen it get. Hot to the point that as I pulled over (bout 2 miles from my house) it just shut off. Waited, refilled radiator, drove home. It ran great until I hit the redlight so it's dependant on airflow to stay cool. So the fan clutch was my first thought, it's old. So is the radiator, 249,000 miles old to be exact. So I waited for it to cool off, changed to a new, functional thermostat, refilled the radiator and drove about 40 more miles. Same thing, hotter than haites. Concluded that as long as I was driving at least 45-50 mph, it would stay cool. Also determined that the engine still had some air trapped inside because of the lack of heat flowing from the vents. So Saturday morning I took off for the trip back to the hometown. Truck ran great, as long as it was moving. Felt damn good to be sitting behind the wheel again, but felt horrible not knowing what was going to happen on the way home. Had to stop once and of course it overheated, so I let it cool, refilled the radiator and drove on home. Made it in one piece, pulled into the drive with the temperature hand sitting on a solid H because of having to negotiate stop signs and little old ladies driving volvo's. <img src="/forums/images/graemlins/angry.gif" alt="" /> Of all the things that I think could be making this thing overheat; air in the system, old radiator, fan clutch shot, blown head gasket or cracked head <img src="/forums/images/graemlins/scared.gif" alt="" /> , I was wondering if the guru's here could lend some info or opinions. The oil shows no water in it, nothing is leaking from the heater core, no antifreeze smell inside the vehicle. Every time I refilled the radiator, it would take up to 60-70 oz of water. Another concern I had, not related to overheating. While the 2.8 was still in, the oil cooler hoses started leaking from where it attaches to the block. These same mechanics used an adaptor that was slightly modified to eliminate the oil cooler. This was by my choice, but I was wondering if that is ok. Essentially, it just blocks ability for the oil to flow from the outlet and back into the inlet. If those two holes are blocked, will there still be oil flow throughout the engine or will it stop right there? I know that was a little confusing but I don't really know any other way to explain. So, if your still reading this, here's comes the main questions:
1. Is my old radiator, or a new 2.8 radiator, going to be sufficient to cool the 3.4?
2. Where could the water be going? It doesn't appear to be leaking from anywhere but the over flow cap (little spout) when up to operating temp.
3. Will my 2.8 heads work on this engine (3.4)?
4. Will electric fans be a better choice instead of buying a new fan clutch?
5. Is it useless to put a 4.3 TBI without boring the intake?

Again, sorry for the length of this. Any help you guys have is appreciated. I really hope to be sharing some good news and pictures real soon. It's been killing me the past 4 months to leave my truck in the hands of some guys that I don't know. I moved to this area about a year ago and have regretted taking it anywhere but places I know of back home in the first place. It's a bit hard when you don't know the reputations, don't have a shop anymore and your DD is about to throw a rod bearing. At that time I lived about 30 miles from work and was getting pretty damned desperate, afraid I might lose the job I moved here for cause I couldn't get to work! But anyway my father has it now and has already flushed the system to elimiate the airlock and found a 93 Astro 4.3 TBI and injectors to put on. He's mostly worried about a cracked head or head related problem. Thanks for taking the time to read and respond if you can.

JC

Yes, the radiator replace it with new or have a good radiator shop clean it.

Make sure the system is properly burped, fill with coolant. Allow engine to warm up with radiator cap off. When thermostat opens, top off with more coolant.

Make sure the overflow tank hoses are properly connected. Hose from radiator goes to the top of overflow barb with the pickup tube sticking in coolant. Other hose is overflow it goes toward the ground. <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> Dont ask how I learned this ... It wasn't my doing.

I dunno, as long as the 3.4 is good don't sweat it.

When my truck starts up cold it really roars,when up to temp hte clutch releases. If the truck gets hot, raise the hood while running yo should feel plenty of airflow. If you still can't tell for sure. Turn the engine off. Grab the fan under the hood you should feel some resistance. I stll use a cleaned factory radiator and clutch fan.

Pretty much. It can be done after swap. Remove the 2.8 TBI, take rags soaked in motor oil, pack the rags down in the intake manifold. The theory is the rags will catch the aluminum shaving. Before removing the rags run a good strong shop vacuum around the intake manifold, to suck up all the loose stuff. Carefully remove rags, repeat with the shop vacuum. If you have any doubt about aluminum shaving falling into the motor. Remove the intake manifold. Do not start the truck.

JC, here goes:

1. Yes. My 3.4 has no problem staying cool with a 2-row aftermarket radiator. 70 mph on the cruise control in 5th, going up I-5 out of Portland, Ore while pulling a 2000+ lb load, in 85+ deg F summer heat !! And barely nudging the temp gage towards 1/2.

2. You probably have a plugged radiator and the all the water is being blown out the overflow. You can easily lose a ton of water this way if you're running on "H" all the time (which ain't so good for the motor, natch!!). Pull your radiator out and have it flow checked, you'll probably find it's at least 75 percent clogged. Try www.radiatorbarn.com for decent deals on a new rad. BTW to properly 'burp' the air out of the system, you need to point it uphill and run with the cap off (starting from cold, of course!) for a few minutes. Then top off. Also be sure you use the correct thermostat (190-195 deg). You can verify the fan clutch is working, as when you're quite hot under the hood the fan should be moving like crazy and you'll definitely hear it blowing. If it's just lazily spinning around, the clutch is shot.

3. Same heads as a 3.4, you really don't need to worry about using the old 2.8 heads. If you want to rebuild them for whatever purpose, you should have the machine shop check them for cracks.

4. No! A properly working clutch fan is more than adequate to cool your motor in 'normal' applications. See #2 !

5. Pretty much. You may get a small benefit from the larger-throated TBI but obviously no way you'll ever flow to full potential without boring the intake. Quite easily done once it's off the motor. Just get a base gasket from a GM 4.3 TBI and use as a template to lay out the holes. Take it to your friendly local machinist and you'll get it back all nice and pretty. BTW tell the parts counter guy you've got a '90 S-10 with 4.3 TBI and it'll make it a lot easier. BTW if you don't bore the intake and do use a 4.3 TBI, you'll have to run some kind of spacer as the 4.3's throttle plates will hit the intake when opened. When you order gaskets for the conversion, you can use 2.8 or 3.4 stuff. You may find good deals on 2.8 gasket sets on eBay. The head gaskets are different of course, but everything else will pretty much fit.

And regarding your oil cooler, nice to have but seems to be a real pain if there are problems with the hoses. As long as you have oil pressure on your gage I don't expect blocking them off has harmed anything.

HTH..........ed

I had some relatively minor overheating problems with my 93 when I bought it...got a new radiator from partstrain.com for $130 (different engine than yours, of course), well worth it IMO. Problem solved, peace of mind, etc. for not too much money...

Check if there is water going out from the tail pipe, also check the water pump and hoses leaking.

Thanks for the help guys. Something I forgot to mention in the first post. My girlfriend was following me on the trip home. There was one time that she called and asked if I had turned on my winshield washers because something "misted" her windshield that appeared to come from my truck. It was a bright sunny day with no water ont he road and at that time I know that no other vehicle was passing us. Anyway about 30 seconds prior to her calling, I switched my heater controls from bi-level to vent and felt a very minor difference in the engine. Nothing alarming, sort of that feeling you get when you turn off your a/c, like it takes a small load off the engine. The thing is, the mechanics told me that they didn't refill my coolant (freon) in the system. Granted the temperature of my interior heater control was set on hot. Not sure what that means. Anyway, it was a one time thing. Had the water come from the tailpipe consistantly, she would have known it. Again, thanks for the help. Any other thoughts I would love to hear.

JC

If there is water going out of the tailpipe maybe is the head gasket, try this, put your truck in neutral, and put the tailpipe near a white surface (a sheet of paper will work) and push the gas at normal highway RPM (3500/4000 RPM) and check if the paper gets wet.

Update... my gracious father has let me know this evening that he got the correct fan clutch (thermal), stuck it on there and it's working well. He also let me know that he simply used the injectors vs. swapping the TBI and injectors both. That also seems to be working good. During a test drive the temp never got over 1/4 on the gauge, after the drive and/or sitting still at stop signs etc. Happy day. So now that's it's cooling ok, he says he may wait on the radiator until a bit later (less $ for me to owe him). Over the next couple of months, I should certainly be able to swap out the radiator but in the meantime I will certainly ask him to have it cleaned properly or possibly fixed (recored) if possible. As for the airlock, nothing mentioned as of yet. He is concerned for the possiblity of engine damage relating to it getting as hot as it did. Are the heads on this and/or the 2.8 aluminum? The 3.4 is from a firebird...supposedly. Unfortunately I didn't get to see the car it came from, just the engine hanging from a crane. Been a long day here at work, first time we've filled all the beds here at the hospital. I work on a gero/psych ward and was hoping they would save me a bed here if I blew this 3.4 to hell...going home. Good evening.

JC

If the head gaskets ain't blown by now they likely won't! <img src="/forums/images/graemlins/notooth.gif" alt="" /> The RWD rigs have cast-iron heads so they are a bit more durable than the front-drivers. They typically don't suffer from the Dreaded Crack-Head Syndrome (DCHS) as do the ZuZu 4-cyl motors.

Way back in '97 after I got my first '90 Troop 2.8 LS it blew a heater hose on the way to Home Base. I managed to coast it downhill and get it into the parking lot, where I picked up a screwdriver and cutting utensils, dressed up the hose, filled up the rad with some bottled water and off she went. After she blew the hose, the temp gage was hovering up by the "H".

It had 130K on the clock at the time; ran the tar out of it until I sold it to my folks in '03 and it's got over 160K on it now.

Never a problem with the motor and it still is a strong runner for a 2.8.

Anyway, if the head gaskets do blow, it'll just give you a good excuse to plant a 3.4 in there! <img src="/forums/images/graemlins/lol.gif" alt="" />

Anyway, if the head gaskets do blow, it'll just give you a good excuse to plant a 3.4 in there!

Psssst, Ed. He did put a 3.4 in there. [/whisper]

Michael