A hydraulic valve lifter, also known as a hydraulic tappet or a hydraulic lash adjuster, is for maintaining zero valve clearance in an engine. The normal method of adjusting valve actuation usually requires a small gap to be left between the valve and its rocker or cam follower to allow for thermal expansion and wear. The hydraulic lifter was designed to operate with zero clearance, leading to quieter running and eliminating the need for adjustment of valve clearance.
The hydraulic lifter consists of a hollow expanding piston situated between the camshaft and valve. In most Mitsubishi engines it is operated by a rocker mechanism. The lifter is filled with engine oil intermittently from an oil gallery via a small drilled hole. When the engine valve is closed, the lifter is free to fill with oil. When the valve is opening and the lifter is being operated by the camshaft, the oil feed is blocked and the lifter acts just as a solid one would, the oil being incompressible.
The reasons for failure can be quite varied from simply wearing out and jamming to no longer holding pressure, or simply filling with grit/worn metal particles.
This can be exacerbated by running poor quality oil, on EVO/GTO/FTO and other performance vehicles we recommend a Fully synthetic ester based oil & on lesser performance cars a Semi Synthetic oil .
Finally it is a myth that Tappets/Lash Adjusters can be ‘pumped up’ by oil pressure, there is simply not enough pressure from the oil pump to do this, the ‘pumping up’ is caused by weak Engine Valve springs and causes ‘valve float’ at high rpm and so the tappet does it’s job to take up the slack and expands to the point of keeping the engine valve open when it should be closed!
There are many manufacturers of Hydraulic tappets.
Not all are of good quality or finish and some have poor internal spring rate.
We have spent years searching for a top quality supplier for our lash adjusters and wanted, at the same time, to be able to buy in such quantities that we could supply lifters at a good deal less than OE dealer prices. This is why we buy/stock lash adjusters by the thousands. Our Tappets come Pre-Filled Ready to Fit - NO BLEEDING REQUIRED
All our Mitsubishi fitments come with a 3mm diameter oil hole for better circulation in the heads and are fitted with heavy duty internal springs for a long working life. The older style OEM ones had a 1mm hole they were very prone to blocking up and seizing giving the dreaded tick tick tappet knock.
All our tappets are 100% Factory inspected for hole size, finish & operation. The best bit is all our Tappets come with a full 12 month Warranty. This proves how much we rate our lifters over our competitors offerings.
How to bleed hydraulic lifters correctly - NOT TO BE DONE TO NEW TAPPETS WHICH COME PRE-FILLED
Hydraulic tappets come in many shapes and sizes but all are bled in a similar manner.
By far the easiest and most readily available for bleeding tappets is a simple large paper clip or 1mm allen key. Open half of the paper clip so you have a straight length or use longer length side of allen key, this you then insert into the top oil hole straight down the middle. Slowly feel your way around and at the same time applying a small amount of pressure downwards, you are trying to locate a tiny ball bearing. You will know when you get it just right as it will suddenly give. Once you have located the ball bearing valve continue to apply light pressure and at the same time hold the tappet upside down and pump the tappet top up and down, this will release the oil. Once the tappet top is moving up and down freely and oil has stopped coming out, then do exactly the same to the rest of them. Then Refill as per the FULL Instructions from the Mitsubishi Service Manual Below.
A NOTE OF CAUTION
DON’T apply too much force to the small ball bearing valve as this will result in it coming away from its fixed position or damaging the tiny spring it sits on and once this has happened it will never seal properly and have to be binned. Only a couple of ounces of pressure is needed to release the valve.
Due to the ease with which these can be damaged we WILL warranty any affected tappets BUT we will NOT entertain any labour claims for faulty tappets.
Taking out of your old worn tappets, and putting back with the new, should really be done using the special tool made for the job. It’s not only quicker but saves fingers and hands from getting stabbed from using screw drivers and the like, that are not meant for the job, and can easily slip.
It’s your pride and joy so do as you wish.
Below shows proper use of removal tool
Below is from the Mitsubishi Service manual regarding cleaning and fitting/refitting if you don't follow it your accepting liability for any problems you may encounter
Below are some of the various type of Lash adjusters & final picture shows breakdown of an EVO/GTO Tappet.
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