Vaalve clearances on diesels.....

Submitted: Sunday, Jun 11, 2006 at 03:56
ThreadID: 34807 Views:2001 Replies:3 FollowUps:3
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does everybody stick to them? About to put my 93 80 series in for a service and was wondering what others thought. Do incorrect valve clearances cause damage, or just affect the runnng of the motor? My terminolology might give away my lack of mechanical skills? The truck had 105k on the clock when I bought it(now up to 125k) and I had a major sercvice done including timing belt, even though I had the service history(never know who the owner knows!). Only realised when I wanted to book in for the next major service that the valve clearances hadn't been done the first time. Yeah I know, should have checked. So now I'm worried it may not have been done for yonks.
Secondly, I get this weird sound after start up ,about 5 seconds later a hissing. I've done it with the bonnet up and think the sound comes from the right side (looking from the front) of the engine bay and low down. I have monitered when it happens ie warm engine, cold engine, perhaps it is more likely at cold but not always. Hoping it is not the oil pump.
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Reply By: Peter 2 - Sunday, Jun 11, 2006 at 08:01

Sunday, Jun 11, 2006 at 08:01
I gather you have a diesel 1HZ engine?
If that is the case then yes the valve clearances are rarely (read never) checked especially at dealers.
You need a special tool to depress the buckets and lift the shims out and most places don't have them. You can do it with a couple of small screwdrivers but it is fiddly, see the Gregory's manual for details.
1HZ's do go better after the clearances have been set correctly, once done they don't seem to change much either. We monitored about 6 or 7 engines over 200k each and they rarely needed adjustment after the first one.
Peter
1996 Oka Motorhome

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Follow Up By: Member - Bware (Tweed Valley) - Sunday, Jun 11, 2006 at 14:47

Sunday, Jun 11, 2006 at 14:47
Thanks Peter, yes that's the engine. Have consulted Gregory and decided it's not my job! Thanks for the info.
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Reply By: Footloose - Sunday, Jun 11, 2006 at 10:41

Sunday, Jun 11, 2006 at 10:41
Valve clearance isn't usually a huge problem with the 1Hz. To do properly requires a lot of labour (fiddly). At around 200K I'd replace the water pump, thermostat and clutch as preventative maintainance. Always use Toyota coolant, anything else leads to strife I'm told. Fit a low/no water alarm, it will set your mind at rest. Those radiators don't last forever. Also have your mech check out your clutch fan and pop some grease in it, another trap for young players :) Check your steering fluid and watch for leaks; its extremely common.
You might also think about joining the 80 series online Qld mob, a great resource.
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Follow Up By: Member - Bware (Tweed Valley) - Sunday, Jun 11, 2006 at 14:53

Sunday, Jun 11, 2006 at 14:53
Cheers Footloose, thanks for all the extra tips. My radiator already didn't last forever :-(
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Reply By: Ian from Thermoguard Instruments - Sunday, Jun 11, 2006 at 11:47

Sunday, Jun 11, 2006 at 11:47
Hi Bware,

Back to your original questions, "Do incorrect valve clearances cause damage, or just affect the running of the motor?", the answers are "yes" and "yes". The possible effects of incorrect clearances depend on whether they are too small (tight) or too large (loose). Too large is the lesser of two evils.

The whole point of having valve clearances is to ensure the valves always close tightly when not being positively opened by the camshaft. The manufacturers recommended clearances (which may be specified for either a "cold" or "warm" engine) are worked out so that, at normal operating temperature, there is still a small clearance despite all the metal components of the valve train having heated up and expanded in size slightly.

If there's no clearance, the valve may be being held slightly open when it should be closed. This is obviously not a good thing as, for a start it means compression will be lost. It's especially bad for the exhaust valves, as a non-sealing exhaust valve will overheat and be eroded, along with it's seat. And once it's badly worn, it's big $ to have the head reconditioned.

Excessive clearance is not so serious a problem but it does mean the valve gear is generally noisy and rattly and it also means the valves are never being opened as fully or for quite as long as the manufacturer intended, leading to lost performance.

I have no first hand experience with 1HZ engine but it sounds like it is a shim-and-bucket arrangement, where the clearance is adjusted by changing a hardened steel shim (probably the size of a coin) to one slightly thicker or thinner, if it is not correct. I can say that my experience with similar systems is that, like the other writers, they rarely require changing once the initial wear is taken care of. The clearances of this type of system are much less likely to change between services than the traditional 'screw and locknut' tappet arrangement.

Now, I'm sure the others will correct me if I'm wrong here but, even if a special tools is required to change any shims, it should be quite feasible to "check" the clearances and determined if any require attention with just ordinary old feeler gauges? On my now 20 year old BMW motorcycle, I used to check the clearances one evening, then if any required changing, I'd go and buy the required shim(s) the next day and change them the following evening (with the special tool, which wasn't too expensive for that engine). With a manual to give you the procedure, I'm sure most home mechanics could easily check their clearances and take the vehicle to a suitably-equipped mechanic if any need attention.
Ian
AnswerID: 177931

Follow Up By: Member - Bware (Tweed Valley) - Sunday, Jun 11, 2006 at 15:02

Sunday, Jun 11, 2006 at 15:02
Thanks for the free lesson, Ian. Being able to check maybe all I need to do to save some big bucks.
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