Thermal valve clearance (VW Golf 1)

Contents: Thermal clearance too small ↓ Thermal clearance too large ↓ Checking the thermal gap ↓ Correctly set valve clearance ↓

Due to engine heating, individual valve parts expand and lengthen. Therefore, there must be a small gap between the camshaft and the cup tappets. Only then can the valves be properly sealed even in a hot engine, despite the lengthening of their stems.

Below we will list the consequences of an incorrectly set valve clearance.

Thermal clearance too small

The valves do not fit tightly to the seats, very hot exhaust valves cannot transfer heat to the seat chamfers because of this. Then the valves and their seats burn out, since hot combustion products pass through the latter. In milder cases, the valves are warped. The seal is damaged, as a result of which the seat soon burns out. Compression decreases, the engine loses power, runs worse and consumes more fuel.

Thermal clearance too large

The valves open a little later than usual: the cylinders are filled worse, the engine does not develop full power. The wear of the camshaft and the adjusting washer, folded at the top into the cup tappet, becomes greater. This is evidenced by the loud noise coming from the valves.

Checking the thermal gap

You can check the thermal gap yourself. The engine must be warm to check (the coolant temperature is 35 degrees Celsius). This is achieved after idling the engine for about 5 minutes. When reinstalling the valve cover, a new seal should be inserted to avoid leaks (three parts).

Remove the valve cover.
Measurements are taken simultaneously at the inlet and outlet valves of the cylinder. The valves must be in a free state.
Turn the engine crankshaft manually until the tips of both cams on the camshaft at the first cylinder point upward.
First try inserting a feeler gauge that matches the upper tolerance value between the camshaft and the tappet (see table below), then insert thinner sheets equal to 0.05 mm.
The feeler gauge for the smaller value should be inserted with slight resistance, otherwise the valve clearance is too small
Less often, the gap is too large, then you can insert a feeler gauge sheet that is thicker than the specified upper tolerance limit.
Record the measured value.
In accordance with the operating procedure, the 3rd cylinder (1-3-4-2) is then checked.
To do this, the engine crankshaft should be turned another 1/2 turn. Now, at the 3rd cylinder, both camshaft cams should be facing upwards. You can take a measurement at cylinder 3.
Check the remaining cylinders in the same way. To do this, turn the engine crankshaft 1-2 turns further.

Correctly set valve clearance

The table shows the values within which the valve clearance should be at a coolant temperature of 35 degrees Celsius.

The figure shows a feeler gauge that is inserted at the 4th cylinder to measure the thermal valve clearance. The clearance of the intake valves should be 0.20-0.30 mm, and the exhaust valves should be 0.40-0.50 mm. These parameters are given for a warm engine. To measure the valve clearance of any cylinder, both camshaft cams should be facing outward (mirror image inverted), as the arrows show.