1988 GMC Vandura 5.7L Weird Overheating Issue (A-Team Drift Van)

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L31MaxExpress

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A more involve method that I have had to resort to a couple of times to check for cracked heads and blown head gaskets that do not show with a block gas test. Get a cooling system pressure tester. With a cold engine, remove all the spark plugs. Hook up the tester and pump the cooling system up to 16 psi. Walk away for several hours. Check the pressure when you return. I had a Sentra that would only overheat when driving and it would blow coolant out of it. Also had a hard start and rough idle after sitting. Well it passed the block gas test multiple times. I pulled the plugs and pumped it up. Ended up letting it sit overnight. When I looked into the spark plug holes, cylinders 2 and 3 had coolant standing on the pistons. On a van you cannot easily see the inside of the engine through the spark plug holes. However if you crank it over with all the plugs out and the ignition disabled, if coolant is leaking into the cylinder spinning the engine over will spit it out of the leaking cylinder.
 

VanGasm

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The flex fan is probably your issue entirely. Vans and flex fans or electrics generally do not get along well together. The flex fans flatten out as the RPM increases and will not pull enough air to cool the engine. An 18" flex fan is rated to cool a 4.0L engine without ac. Electrics have ok cfm at idle but nowhere near the CFM a good clutch fan can pull. Get an 11 blade pastic fan and a proper clutch and put it on there. A factory shroud should also be in place. A factory small block G-van prior to the front end update in about 1992 was a 28x17x1.25" core. With a proper functioning clutch fan my 83 stayed cool even with the ac cranked up and a trailer behind it.

I have also seen several fans installed backwards or were the wrong rotation. At idle they stayed cool and cruising at moderate speeds they overheated. At high speeds like 70-80 mph they cooled fine. With the engine running make sure the fan is pulling air and not pushing air. I worked on a 5.0L Mustang once that the owner had been fighting an overheating issue on. It was winter time in Texas. I changed the thermostat, verified it was burped and coolant was flowing. Ran it several hours and then took it for a test drive at highway speeds. It ran cool and I though all was good. It comes back in around May. It was overheating and the ac had popped off the high pressure relief valve and let alot of refrigerant out. So I ask question and fibd out it overheats at about 30-50 mph around town. AC had been cold at idle and warm at the same speed. Anyway I get it in the bay of the shop. Go over some stuff. I evac and re harge the ac. Get the car up to temp. Now it is in the mid 90s in thr shop and I have shorts on. As the car warms up, I suddenly notice hot air is blowing against my legs. It had a CW rotation flex fan on a CCW rotation pump. The car was cooling ok at idle when it was stationary but the fan was causing airflow to stall in that 30-50 mph range. When driven faster the ramming effect of the air entering the grille overcame the flex fan and cooled the car.
Thanks for the help and support on this.

I think the issue was a "duh" moment.

Loosened the radiator cap, drove it up my test hill, temp climbed to 240, then immediately slammed back down to 160. Checked the radiator and the fluid was significantly down. Bottom line: I think it was a large bubble. The water pump on it isn't the best, but the only one I could find in the local area that was a true reverse rotation. Reading about standard small block water pressure, they push about 50gpm at 13psi. The radiator cap is 16psi.

After this test run, I filled it back up and it's been running at operating temp (actually a few degrees cooler than it has been running for the last month) on all test runs. Completely let it cool down last night. Checked it this morning and the reservoir sucked from the warm mark to the cool mark. Gonna run it into Seattle today with a bunch of good hills in there to triple check it.

Thanks for the confirmation on the radiator size. The correct radiator is in it.

This thing is meant to be tracked for short runs on film. That said, I wanted to make sure it was at least running well under standard load. Had a couple different mechanics looking at it and it's moving a ****-ton of air between the aluminum flex fan and big electric fan. The shroud is on and the fan is correctly sized and positioned to not cavitate air and pull the right amount through the radiator. All fans are triple checked to be flowing the right direction.

Vans definitely suck for engine temps. Now that I think it's running OK, I'm going to finish putting a couple puller fans in the engine bay with ducting to suck in cool air from the outside. Aiming for 1200cfm into the engine bay to make sure the cold(er) air is displacing the hotter air at the top of the engine bay/doghouse.

Thankful for everybody here and the help. Looking forward to posting the videos of the van doing its thing. This ride definitely generates a ton of smiles, thumbs up, and high fives.

If you guys want to follow the van, hit us up on instagram @van.gasm

Thanks again.
 

VanGasm

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A more involve method that I have had to resort to a couple of times to check for cracked heads and blown head gaskets that do not show with a block gas test. Get a cooling system pressure tester. With a cold engine, remove all the spark plugs. Hook up the tester and pump the cooling system up to 16 psi. Walk away for several hours. Check the pressure when you return. I had a Sentra that would only overheat when driving and it would blow coolant out of it. Also had a hard start and rough idle after sitting. Well it passed the block gas test multiple times. I pulled the plugs and pumped it up. Ended up letting it sit overnight. When I looked into the spark plug holes, cylinders 2 and 3 had coolant standing on the pistons. On a van you cannot easily see the inside of the engine through the spark plug holes. However if you crank it over with all the plugs out and the ignition disabled, if coolant is leaking into the cylinder spinning the engine over will spit it out of the leaking cylinder.
Thanks for the idea. If it's not running correctly after last nights "duh moment" bubble burp, I'll try this.

The engine has lost zero coolant throughout this entire process. No white smoke. No sweet smell out of the exhaust. Passed the block gas test. I really think it was a bubble that didn't get burped as a result of me not burping it correctly the first time with the less than stellar water pump.
 

454cid

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Vans definitely suck for engine temps. Now that I think it's running OK, I'm going to finish putting a couple puller fans in the engine bay with ducting to suck in cool air from the outside. Aiming for 1200cfm into the engine bay to make sure the cold(er) air is displacing the hotter air at the top of the engine bay/doghouse.

I think you would do better to pull hot air out. If you try pushing more air in, you will be fighting your radiator fans.
 

VanGasm

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I think you would do better to pull hot air out. If you try pushing more air in, you will be fighting your radiator fans.
I'd thought about that as well. Installing the puller fans below the driver and passenger seats, then running ducting up behind the air cleaner. Pull the hot air out of the top of the doghouse and have it exit behind down and out behind the doors.
 

gearheadE30

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Was it doing this before you put that 160 degree thermostat in it? You may just have a sticking or weak thermostat.

160 degree stats are also generally too cold for optimal operation for various reasons. I'd recommend a 180 degree if you really want something cooler than stock, but at the end of the day the stat cracking temperature isn't what would cause this specific problem.
 

VanGasm

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Was it doing this before you put that 160 degree thermostat in it? You may just have a sticking or weak thermostat.

160 degree stats are also generally too cold for optimal operation for various reasons. I'd recommend a 180 degree if you really want something cooler than stock, but at the end of the day the stat cracking temperature isn't what would cause this specific problem.
The 160 was the only thermostat put in it after the tune up. The upper radiator hose is flowing well and confirmed everything with an IR temp reader.

I checked with Harris. The Stage 1 chip reaches closed loop at 140 degrees and the motor changes idle at that temp. If you read above, I really think it was a duh moment and simply had a bubble trapped in the motor that was resolved by running with the cap loose up a hill.
 

VanGasm

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So... The saga continues.

Drove the van into Seattle yesterday and it was running perfect temp (actually a few degrees cooler than it had been) and then on the final hill into Seattle with traffic, it started heating up again. Pulled over, let the electric fan run for about 15 seconds. Fired it back up... right back to temp. Parked it for three hours in town, then started the van while staring at the exhaust... small puff of white smoke upon startup. FML--head gasket.

Drove it home and it stayed generally in range with only another heat up, 30 second rest, and back to temp episode. My thought is that exhaust gases are getting into the cooling jackets and heating up the motor. Checked the resevoir and saw the smallest of bubbles rising up into the tank. Another indicator of a blown head gasket. FMLx2

Thinking back on it, I bought this van about a year ago after begging the previous owner to sell it to me for three years. Out of the blue, they sold it to me. My first mod was to put on the exhaust before doing the major overhaul. On the way back from the exhaust shop, it overheated. Thought it was a stuck thermostat. So, I did the full tune up with replacement thermostat, new radiator, new water pump, etc, etc, etc.

My mechanic recommended the Blue Devil head gasket sealer. The internet recommends it. Went through the entire process. Drained coolant. Removed thermostat. Hose flushed the motor for 10 minutes. Hose flushed the radiator. Did the true flush with a chemical flush. Cooled the motor. Drained. Went through the blue devil process and idled for 50 minutes. Went through the entire cooling cycle overnight. Got up early this morning. Drained the blue devil, reinstalled thermostat, new coolant, burped motor, and gave it a test run.

No white smoke on startup. Temp holds solid on level and throughout town. Heating up on uphill.

SO... it's one of two things.

1) The flex fan simply just isn't moving enough air through the radiator and engine bay. Old adage... "If you want to rock, leave it stock."

2) There's a leak somewhere that the blue devil simply can't fix. Will pressure test the motor overnight and check for fluid in the cylinders.

FML
 

Frank Enstein

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A few things come to mind.

1) too much antifreeze in the mix will interfere with heat transfer. Water transfers heat 4 times as well as antifreeze.
Zero degrees F or 10 degrees F colder than the vehicle will see is the optimum mix of antifreeze/water.
You need some antifreeze to prevent corrosion and to lube the water pump seals.

If it absolutely never ever freezes where the car lives you can double up on the additives (see below) and run drinking water with it.
Radiator manufacturers do not recommend distilled water. They say it can lead to leaching minerals from the metals in the cooling system.

2) Not using a pressure balanced thermostat. One that looks like this;
Standard thermostats can be stuck shut by the water pump flow especially at higher rpm.
This causes wide swings in the coolant temp.
In my opinion this is the most likely cause of your symptoms.

3) Timing retarded from where it should be at the conditions it heats up. That's in the tuning software.

4) Airflow management.
Make sure all the air that comes in the grille has to get through the radiator to get out.
Make sure all the air from the radiator has to go through the fan/shroud to get out.
Extend the bottom of the air dam to the bottom of the radiator support. Doing that will increase pressure in front of the radiator but more importantly it will pull hot air out of the engine compartment so more cool air can go through the radiator.

5) Chemical help;
The Redline Super Cool with water wetter or Royal Purple purple ice will break the surface tension of the coolant which prevents nucleate boiling and improves heat transfer.

Finally experiment with blocking off sections of the grille. It sounds counterintuitive but blocking part of the grille will reduce the amount of air trapped in the engine compartment allowing more net airflow across the radiator. Maybe.:biggrin:
 

CrustyJunker

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Sounds like a cool project! I know you're not asking...But if the head gasket is actually bad the right thing to do is change it (or both in your best interest). Especially if this is going to be an actual "drift van," do it the right way and you won't be disappointed.

I know there's some bandaid fixes in a bottle to get you home...But sometimes those fixes show up later in the form of clogged coolant passages, heater core, or blocking some tubes in your new radiator causing other inefficiencies.
 
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