When it comes to Cylinder Heads in the Trade machine shop at www.rpmengines.com.au we are machining and reconditioning any where from 10 - 20 per week ! from Cars - Trucks - bikes - boats .
But What causes them to fail ? This Blog I'm going to touch on a few reasons but there are too many to itemize.
Some heads come in with slight warping, a crappy looking surface and usually this day in age carboned up with baked on dirty oily sap.
First is first, Engine has got hot, warm etc. Due to other cooling system components such as radiator being partially blocked or just out right stuffed, leaking cooling system hoses remember there is a tone of them it does not take much for one to start weeping then you are down on your vehicles desired amount of coolant. Water pump has stopped churning over the flow through the engine, coolant boils off in the block etc. Thermostat blocks and stops the flow. Or Maybe a cooling fan has slowed down or even stopped. ( still enough to do some Van-Damage ).
In Late model vehicles a very common but un-known factor is an egr cooler, yes this cooler cools the exhaust gases before returning them to the intake system, well these Mofo's leak internally, sometimes it can be an absolute painful time picking up the fault until you have replaced everything else.
"**** I hear some ford ranger and mazda bt50 guys out there yelling at their device screen as they are reading this blog , Saying EGR Cooler GRRR yes Yes Yes and some swear words also. ****"
The other factors are burned valves and valve seats very common on LPG vehicles or vehicles that have a crappy fuel injectors or ecu fault causing a cylinder or more to run lean over a period of time.
this is where a great technician with a scan tool these days can tell you what your vehicle is doing by checking out your oxygen sensor live data.
( You need a Technician who understands them, this can be the difference between paying $80 for a scan and diagnostic time in a workshop to paying $30 for a scan for just a code, as the diagnostic tools have so many more functions these days and technicians require special training to use some of their features.
But when it comes to a fuel injector " talking efi " with a bad flow patern or poor flow as well as machining the heads we strongly suggest to our clients we flow their injectors & recondition them before re assembling. In which we can do in house for ourselves and all of our trade clients.
Another important thing or detail with cooling systems on modern vehicles is the temp gauge may only rise once when the coolant does not flow around the probe of the sensor in the engine. But then can return to near normal operating temperature display on the dash as it is now operating on steam in the engine as the coolant is boiling away in the engine block or below the probe area. It is important to check your temp gauge as much as your fuel or speedometer as you may only get one chance to pull over before major damage occurs.
When a vehicle comes in presenting head faults normal procedure is to carry out a TK test, pressure test, leak down or compression test to see what type head problem we are dealing with. A TK test is great for checking if you have exhaust gases in the cooling system, a pressure test can do the same to see if you are building pressure in the cooling system or also loosing pressure due to a leak. A compression wet and dry test will indicate a valve or a cylinder fault like wise a cylinder leak down test.
So in www.rpmengines.com.au , engine reconditioning shop your Gonna spend some money on doing your cylinder head. So you may as well do it correct the first time.
1st step is striping and cleaning, this means removing the valves and de-greasing the head to see what is going on.
step 2: heated bench Pressure test to test for cracks, this will indicate if the head is repairable or a new head is required.
step 3: a solid clean usually means soda blasting. to make it look brand new also to remove build up carbon etc.
now to start the machining. All valves are now checked and if suitable to be reconditioned cleaned & machine faced.
Valve seats same if worthy are now re-cut back to original specified angles. the cylinder head if within spec now machine faced. head is dummy assembled and valves tips are machined for correct rocker geometry where required.
the head depending on style, ( shimmed , hydraulic or adjustable may require other machining or cleaning. )
The head and all its components are now chemically cleaned and dry cleaned for final assembly.
then upon final inspection a HEAT TAB glued on the closest water port or gallery area.
HEAT TABS are important ! they tell the machine shop or the Technician when or in some cases how bad a vehicle has been overheated or driven whilst warm or hot.
Now the complicated stuff is out of the way the engine block surface must be prepared and cleaned. sometimes multiple times.
The new head gasket laid as per gasket manufacturers specs. the detail of this some times come part of your VRS gasket set. but can be found on special programs such as auto data or some automotive engine shops may print them out for you for a small fee.
A lot of manufacturers these days use stretch head bolts. this means yes they must be replaced, so as well as your VRS head gasket set you will require new head bolts.
The other vital parts now you are re assembling your vehicle: have you had your radiator stripped and cleaned out, regardless of age as it does not take much to clog them up, If an engine has boiled a little bit of rusty scale could have been pumped through to your radiator. Now you could have to re-work this entire process for not getting it checked. ( Mark At Nambour Radiators does an amazing job.)
Replace your water pump , thermostat and any hoses that even look the slightest un-desirable. also any poor hose clamps of same nature.
One other thing is the Fan no matter if electric or hub style make sure it is spot on.
Well I hope once again our blog has been informative and keeps you from blowing a head or gasket and gives you a little indication of what your local repairer is doing when they say your vehicle needs a cylinder head repair.
Remember good people of the Sunshine coast, If you do not travel into Kunda Park to visit us as we are out in the industrial estate. But require a recommendation for a local repairer who is close to you, we have a network of Great local independent family owned repairers that are more than likely close to your home or work, who supply our great RPM products and share our fellow workmanship ethics. Please drop us an email or call and we will put you in contact with them.
take care Mr RPM L.B
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