Recently the Land Rover Toolbox Videos were given a challenge to test and review the Paddock Heavy Duty Valve Spring Compressor PM1240. This opportunity we snatch up without second thought. We do love to put tools through their paces. As the name implies, the ‘Heavy Duty Valve Spring Compressor’ is designed for use an a variety of different applications for diesel engine cylinder heads including truck applications. It is the same as those found in truck garages and well suited to the Land Rover engines which by their nature have cylinder head valves that are larger than a small 16 valve car engine. We found the tool is also suited to smaller car engines too utilizing reversible heads for accommodating for a wide range of spring cup sizes . It is robust in construction and at the price Paddock have the tool on offer I would advise using this one. It suits a professional garage environment well having its place firmly on the tool wall.
For an enthusiast that may only recondition a cylinder head perhaps once every 5 years or less depending on the enthusiasts activities, it still is worthy of an earned place in the home DIY garage. You never know when you need to lend it out to a fellow enthusiast or take on a job on family run around or even for use the next classic car restoration project. The tool is a positive investment.
The following article is not a ‘how to change your stems seals’ : we have videos for that on our You Tube channel for that!! It is rather an insight into some of the factors involved in successfully stopping oil consumption and having an efficient and perfectly running engine.
Changing the valve stem seals.
The stem seals on the cylinder head valves play a vital role in stopping oil from traveling down the stems of the valves; getting into the cylinder bores. The tell tale signs of the oil getting past the seals is blueish smoke seen in the exhaust smoke on start up. If you have a nose for it then you will also smell the oil being burned. The symptoms are lacking when the engine is warm. Please do not think that bore wear is ruled out either but oil burning will continue when the engine is warm to some extent if the cylinder bores are worn.
For some of you it may a daunting task to have to remove the cylinder head and pop out the valves to access the seal before changing them but in reality it is an easy job to accomplish with a systematic approach. I will add here that there is more to consider than just replacing the seals however.
Generally one will have to lift the cylinder head off the vehicle and have it on a bench. Even if there are tools to allow one to push the valve springs down to release the retaining collets allowing the valve spring to be removed on the engine I would strongly advise to have the head off the engine and in all cases as you need to check components for wear.
The first thing do is be prepared to measure, measure and measure everything. Checking to see if all the components are within tolerances with the workshop manual data for the engine you are working on. The cylinder head warpage is the first thing to check so after scraping the remains of the composite gasket that was fitted is important. Find yourself fortunate if a tin gasket was fitted. Very little cleaning is needed if one of those was fitted.
You will need to measure across the length width and the diagonals of the face using a feeler gauge measuring the gap, if any, between the face of the cylinder head and the straight edge. As long as this is within data given then proceed otherwise you need to consider replacing the whole head with a new item or find a second hand serviceable replacement. If you were buying a second hand unit then approaching the head with the intention of reconditioning it will pay you dividends and less frustration than fitting it to find it unserviceable.
Removing the stems seals with the cylinder head still in place. This involves having the piston on the relative valves on a piston set at Top Dead Centre ( T.D.C.) which the valve will sit on. Otherwise the valve would drop straight down the cylinder bore! This technique is used on particular engines to set the correct position for setting the diesel pump timing. An example of this is the Peugeot EN 55 and TN70 engines found as a conversion from the LDV convoy 2.5 ltr engine fitted to a few Land Rovers. I would not advise dropping the valve this way unless you know your engine technology well.
Let’s presume you have removed the cylinder head. You may have done this to replace the cylinder head gasket for some reason or specifically want to stop oil consumption from worn valve stem seals. You will need a valve spring compressor. this enables you to compress the spring cup and valve spring releasing the collets. Once the collets have been removed then the valve can be slipped out. Keep all valves in order along with the springs and spring cups. The first thing you are going to have to pay attention to is the condition of the valves with the amount of carbon on them, especially the on exhaust valves. Removing the carbon involves using a rotary wire wheel, either on a bench grinder or on a drill attachment type arrangement. Carbon hinders the gas flow to and from the engine so it is important that it is fully removed. Years ago this would be called ‘de-coking’ usually done at 100 000 miles.
We also need to be able to check the condition of the valve and valve seat in the cylinder head for condition. Carbon can hide a possible failed component so caution is required.
Secondly you need to check the condition of the the valve face and valve seat. These are what make the air tight seal when the valve is closed any pitting on these need to be removed by either lapping the valves in or if excessive, grinding the valve face and cutting the valve seat will be required. Owing to the cost of the tools required it would be best to employ the services of an engineering workshop to carry out this task. It will be wise to check the valve head for cracks or burning once cleaned up. If this is present then the valve / valve seat in the cylinder head will need replacing again the seat will need to be replaced by an engineer. Measuring the valve stem is important. measuring the stem of the valve, top middle and bottom are required. You will need to check your workshop manual for the specific data for the engine. The details will be under “engine data”. The 300tdi engine stem maximum wear tolerance is 7.96mm for instance so any measurement under that on the stem of the valve renders the valve for replacement.
You will need to check the valve guide in the cylinder head. Measuring this is achieved by placing a new valve into the guide, lifting it above the face of the head, and again in the case of the 300tdi engine is 8 mm to the top of the valve head, then the movement of the stem in the guide measured by a dial gauge. This operation is easier than it seams but one need to own and know how to use a dial gauge. Our recent 300tdi project engine cylinder head most of the valves were out of tolerance unfortunately.
Precision measurement and fine tolerances are key to modern engine performances. We firmly out of the age of steam so demanding finer clearances on components leads to efficient working components. Measuring and fitting components to manual data is key to having a better running power plant.
Okay so you have got this far and perhaps all is within tolerance of the workshop data if not then replace as required. It pays to list the measurements on each cylinder number initially so you are working form cylinder 1 through 4. Each valve will also have a number. I usually start at first cylinder number 1 the closest to the timing belt (the French call the cylinder next to the flywheel as number 1 for some odd reason) then number the valves respectively from 1 to 8. Keep it pragmatic.
Lapping the valve faces to valve seat are is required either when fitting the original valve but before you start this ensure the valve stand down is correct. This is where you use a feeler gauge with a straight edge resting on the cylinder head face. You are reading the gap between the valve in the closed position and the cylinder head face edge.
This measurement is vital. Too small and the valve runs the risk of hitting the piston crown.
Measure the valve spring free length. Using a vernier caliper this is easy. Under tolerance means the valve spring will be weak and requires replacing.
The stem seals are available in the cylinder head gasket kit which will usually not include the head gasket. You should have all the gaskets you need (and more) to re assemble the head.
DISCLAIMER: Whilst all efforts to provide professional, accurate and safe educational tutorials covering repair and maintenance of road vehicles are made. The sponsors (Paddock Spares) and makers (Trailerfitters Toolbox) of this blog and video are not liable for any injury or damage to persons or property as a direct result of watching this tutorial. (For full disclaimer please see the end of the above video).