4flyer
Member
Background:
I own a 2001 Toyota 4Runner with ~284k miles. I’ve put 110k of those miles on it myself, though it’s no longer my daily driver. It’s been an exceptional rig, and I’ve made it “mine” with extensive mods and maintenance. I’ve kept up with regular care—Mobil 1 synthetic oil changes every 5k miles since at least 2008, and in my ownership, the engine has never overheated. I monitor engine and transmission temps closely with a ScanGauge II. The truck is in solid shape overall, but I now suspect a blown head gasket or cracked head.
Symptoms:
A few months ago, I noticed extra exhaust smoke on cold starts, which cleared up once warm—I chalked it up to condensation. Over time, a slight misfire appeared at startup, later triggering a P0300 (random misfire) and then a P0303 (cylinder 3 misfire). I also noticed minor coolant loss, which I initially blamed on a loose top radiator hose. Suspicions grew, but since I wasn’t driving it much, I delayed digging in. Recently, I committed to a proper diagnosis. No massive smoke clouds or overheating yet.
Preliminary Diagnosis:
Two weeks ago, I ran a compression test using a loaner tester from O’Reilly’s—my first time doing one. Engine was cold. Results:
• Cylinder 1: 210 PSI
• Cylinder 2: 195 PSI
• Cylinder 3: 180 PSI <---
• Cylinder 4: 210 PSI
• Cylinder 5: 208 PSI
• Cylinder 6: 210 PSI
Cylinder 3 was noticeably lower. A wet test on #3 jumped to 250 PSI (likely too much oil added). The readings seemed high overall, and I didn’t trust the tester, but the delta pointed to an issue on #3, matching the P0303 misfire.
Secondary Diagnosis:
Last weekend, I tested again with a different loaner tester from AutoZone, this time on a warm engine. Results:
• Cylinder 1: 192 PSI
• Cylinder 2: 186 PSI
• Cylinder 3: 167 PSI <---
• Cylinder 4: 192 PSI
• Cylinder 5: 182 PSI
• Cylinder 6: 180 PSI
These felt more realistic for a 5VZ-FE with 284k miles. Still, #3 was below the factory service manual minimum of 174 PSI and exceeded the max allowable delta (15 PSI). Next, I did a leak-down test on #3 with a friend:
• Initial Pressure: 100 PSI
• Ending Pressure: 60 PSI
• Leakage: ~75%
We traced the air—no leaks to the exhaust, intake, or oil system. But when we opened the radiator cap, coolant erupted. Confirmation. Later, with the engine cold, I found a small coolant puddle in #3 via borescope. Other cylinders had typical carbon buildup; #3 was clean—steam-cleaned by coolant, I assume. No coolant in the oil, though.
So, #3 strongly suggests a blown head gasket or cracked head, right? What’s next?
Next Steps:
Assuming my diagnosis holds, I’ve got decisions to make. I want to keep the 4Runner. It’s not my daily anymore, and my plan is to restore it—fix mechanical issues, repaint it, even install new Katzkin leather seats I’ve got sitting ready. Over the last 50k miles, I’ve upgraded CV axles (CVJ), added OME springs and Bilstein shocks, mounted BFG KO2s, and built a dual battery setup, power distribution system, 120V inverter, molle panels, drawer system/sleeping platform, plus ham and CB radios. Put a good deal of work into the rig.
Options:
1. Engine Swap (JDM):
-Nope. I lack the space and gear for a swap, and I’d need a pro. Plus, I don’t trust an old engine with unknown history.
2. Engine Swap (Rebuilt):
-Tempting but pricey—$4,500+ for a Yota1 rebuild. Overkill for a non-daily.
3. New Head Gaskets/Heads:
-Tear down the engine over several weekends, replace head gaskets, and have the heads resurfaced by a pro. If cracked (likely), buy new heads and reassemble.
-Pros: Cheapest fix. Perfect time for water pump, timing belt, hoses, leaky valve covers, maybe a valve adjustment. Basically a whole engine refresh.
-Cons: Super labor-intensive, and surprises could lurk.
4. Sell It:
-Cut losses and regret it into my 50s (I’m not even 30). Not happening.
I’m leaning hard toward Option 3. It’s a chance to learn serious engine work, and with no rush to drive it, I can take my time. It’d refresh the engine and keep her alive. I only plan on doing 5k miles a year from this time out. If I go this route, what else should I tackle while it’s apart? Anything I’m missing?
I own a 2001 Toyota 4Runner with ~284k miles. I’ve put 110k of those miles on it myself, though it’s no longer my daily driver. It’s been an exceptional rig, and I’ve made it “mine” with extensive mods and maintenance. I’ve kept up with regular care—Mobil 1 synthetic oil changes every 5k miles since at least 2008, and in my ownership, the engine has never overheated. I monitor engine and transmission temps closely with a ScanGauge II. The truck is in solid shape overall, but I now suspect a blown head gasket or cracked head.
Symptoms:
A few months ago, I noticed extra exhaust smoke on cold starts, which cleared up once warm—I chalked it up to condensation. Over time, a slight misfire appeared at startup, later triggering a P0300 (random misfire) and then a P0303 (cylinder 3 misfire). I also noticed minor coolant loss, which I initially blamed on a loose top radiator hose. Suspicions grew, but since I wasn’t driving it much, I delayed digging in. Recently, I committed to a proper diagnosis. No massive smoke clouds or overheating yet.
Preliminary Diagnosis:
Two weeks ago, I ran a compression test using a loaner tester from O’Reilly’s—my first time doing one. Engine was cold. Results:
• Cylinder 1: 210 PSI
• Cylinder 2: 195 PSI
• Cylinder 3: 180 PSI <---
• Cylinder 4: 210 PSI
• Cylinder 5: 208 PSI
• Cylinder 6: 210 PSI
Cylinder 3 was noticeably lower. A wet test on #3 jumped to 250 PSI (likely too much oil added). The readings seemed high overall, and I didn’t trust the tester, but the delta pointed to an issue on #3, matching the P0303 misfire.
Secondary Diagnosis:
Last weekend, I tested again with a different loaner tester from AutoZone, this time on a warm engine. Results:
• Cylinder 1: 192 PSI
• Cylinder 2: 186 PSI
• Cylinder 3: 167 PSI <---
• Cylinder 4: 192 PSI
• Cylinder 5: 182 PSI
• Cylinder 6: 180 PSI
These felt more realistic for a 5VZ-FE with 284k miles. Still, #3 was below the factory service manual minimum of 174 PSI and exceeded the max allowable delta (15 PSI). Next, I did a leak-down test on #3 with a friend:
• Initial Pressure: 100 PSI
• Ending Pressure: 60 PSI
• Leakage: ~75%
We traced the air—no leaks to the exhaust, intake, or oil system. But when we opened the radiator cap, coolant erupted. Confirmation. Later, with the engine cold, I found a small coolant puddle in #3 via borescope. Other cylinders had typical carbon buildup; #3 was clean—steam-cleaned by coolant, I assume. No coolant in the oil, though.
So, #3 strongly suggests a blown head gasket or cracked head, right? What’s next?
Next Steps:
Assuming my diagnosis holds, I’ve got decisions to make. I want to keep the 4Runner. It’s not my daily anymore, and my plan is to restore it—fix mechanical issues, repaint it, even install new Katzkin leather seats I’ve got sitting ready. Over the last 50k miles, I’ve upgraded CV axles (CVJ), added OME springs and Bilstein shocks, mounted BFG KO2s, and built a dual battery setup, power distribution system, 120V inverter, molle panels, drawer system/sleeping platform, plus ham and CB radios. Put a good deal of work into the rig.
Options:
1. Engine Swap (JDM):
-Nope. I lack the space and gear for a swap, and I’d need a pro. Plus, I don’t trust an old engine with unknown history.
2. Engine Swap (Rebuilt):
-Tempting but pricey—$4,500+ for a Yota1 rebuild. Overkill for a non-daily.
3. New Head Gaskets/Heads:
-Tear down the engine over several weekends, replace head gaskets, and have the heads resurfaced by a pro. If cracked (likely), buy new heads and reassemble.
-Pros: Cheapest fix. Perfect time for water pump, timing belt, hoses, leaky valve covers, maybe a valve adjustment. Basically a whole engine refresh.
-Cons: Super labor-intensive, and surprises could lurk.
4. Sell It:
-Cut losses and regret it into my 50s (I’m not even 30). Not happening.
I’m leaning hard toward Option 3. It’s a chance to learn serious engine work, and with no rush to drive it, I can take my time. It’d refresh the engine and keep her alive. I only plan on doing 5k miles a year from this time out. If I go this route, what else should I tackle while it’s apart? Anything I’m missing?
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So you can watch a lot of them to get a good feel of what it takes to pull off the 5VZ-FE heads.
