What Actually Happens When You Overheat an Engine

Summary

The hosts intentionally overheat a BMW engine to test its limits. They perform tests showing most cylinders have bad compression leakage. Removing the head reveals clogged coolant passageways likely causing overheating. Valve seats are extremely worn causing loss of power. Surprisingly, apart from warped heads and bad valves, the bottom end looks healthy. The oil protected well against overheating damage. With new head work and valves, the solid engine could be rebuilt.

Takeaways

• 😊The video involves intentionally overheating a BMW engine to test how long it can last before failure.
• 🔥They run laps in the car, revving the engine to increase heat until it overheats.
• 🛠After overheating the engine, they tear it down to diagnose issues and find the root causes.
• ❗Major issues found: warped cylinder head, leaky valves, clogged coolant passages.
• 👍Despite abuse, bottom end and internals are in decent shape, oil system protected well.
• 🔧They methodically check components: thermostat, water pump, head gasket, head, block.
• 😀Final verdict is the engine survived remarkably well, but does need some repairs.
• 🔨Head needs skimming, valves need attention, then it could run again.
• 🏁Key overheating failures: thermostat, water pump, head gasket, cylinder head, piston rings.
• 💡Takeaway: modern engines can survive some abuse if oil system protects well.

Q & A

What is the main goal of this experiment?

The main goal is to intentionally overheat the engine of an old BMW to its limit, in order to observe what fails inside the engine when it overheats.

What are some of the key components that can fail when an engine overheats?

Some key components that can fail include the thermostat, water pump, head gasket, cylinder head, and piston rings.

What does a leakdown test help determine?

A leakdown test helps determine the condition of the cylinders and how much compression is being lost due to leaks.

What was the result of the leakdown test on this BMW engine?

The leakdown test showed very high leakage percentages, especially on cylinders 1, 2, 3 and 4, indicating significant loss of compression.

What was causing the coolant passageways to get blocked in the cylinder head?

The coolant passageways were getting blocked due to buildup of deposits and sediments over time, restricting coolant flow.

How much warpage was found in the cylinder head?

The cylinder head was warped by 0.007 inches, which is way beyond the allowable tolerance of 0.002 inches for this BMW engine.

What was the main issue found with the valves?

11 out of the 12 sets of valves were found to be excessively leaky, resulting in loss of compression.

What protected the bottom end components from damage?

The high quality full synthetic oil protected the bearings, piston rings and other bottom end components from heat damage.

Could this engine be rebuilt and reused?

Yes, with some repairs like skimming the head, valve work and gasket replacement, this engine could be rebuilt and reused.

What could be done to prevent such overheating failures?

Regular maintenance like coolant flushes, valve adjustments, high quality oil and keeping temps in check could prevent such overheating issues.