Club 80-90 Forums

Hi everyone, 

I have a 1987 T3 with a 1.7 KY diesel and 4 speed. I have been a bit stumped by running issue in the vehicle and wanted to reach out to other members who might have some experience with this. 

I have owned the T3 for nearly 1 year and it has been fantastic and reliable. Last summer I  changed the head gasket, water pump and cooling system. When the head was off, I had at pressure tested and surfaced.  Everything looked good. I didn't check valve clearances at this point. 

Engine runs strong, at good temperature, starts up no problem. Ever since the rebuild, I get a mechanical resonance at a specific RPM range (in all gears). It occurs at between 65 to 70 km/h while in 4th gear and the similar RPM range for all other gears. It has a light metalic tone to it, but its really hard to pin down where its coming from. 

I thought it might be the metallic shroud/heat shield between the exhaust and the motor but removing this has not changed anything. I am wondering if this sounds like a valve clearance issue? The fact that it really only occurs at a specific RPM range is a bit confusing to me. 

If anyone has experienced this I would be interested to hear your thoughts or experience. 

I think if you can make out a light metallic tone, you’re doing really well. It’s a regular joke on here that diesels are v noisy.

Aside from that, do you wonder if it’s running better/more powerfully since the rebuild? I’d be wondering, if so, about it being exhaust noise or from the intake snorkel or the pipe below it vibrating the rear quarter internally. Other than that, could be anywhere...

So you had a reliable van . Then the head was took off and skimmed (fixed something that wasn’t broke) vw says the head should not be skimmed ! 
,so might it be the compression ratio is now too high and might that cause the diesel equivalent to “pinking” you get with a petrol engine.or maybe the pistons are hitting the valves! Hopefully not the latter given the noise is at a particular rpm.
Different thickness head gaskets are available ,was the correct one to use correctly determined?
Valve adjustments are something which should be done before something breaks !

^^^^^ WHS x2.
Who decided that the head should be skimmed against VW's stipulations, if a garage change your garage/mechanic.

No problem skimming diesel heads almost all manufacturers say not to skim them but there’s been people skimming them for years, I had literally hundreds done and never had an issue, the are flat and don’t effect compression, the distance from valve to piston is the main issue. It’s unlikely to be the engine itself causing the resonance

Maybe some ancillary component, I would suspect gearbox first . Have you had someone look over it ,?

Check tyres condition, balance or damage wheel bearings, , drive shafts , engine and gearbox mounts. Can you get the resonance by revving the engine whilst stationary?

davidoft1 wrote: ↑13 Mar 2021, 11:52 No problem skimming diesel heads almost all manufacturers say not to skim them but there’s been people skimming them for years, I had literally hundreds done and never had an issue, the are flat and don’t effect compression, the distance from valve to piston is the main issue. It’s unlikely to be the engine itself causing the resonance

Maybe some ancillary component, I would suspect gearbox first . Have you had someone look over it ,?

Check tyres condition, balance or damage wheel bearings, , drive shafts , engine and gearbox mounts. Can you get the resonance by revving the engine whilst stationary?

I see your point about the flat surface of the head not leading to a higher compression ratio and interesting to learn of your experience with skimming of heads.
 

The machine shop recommended skimming after it was pressure tested and measured. The thicker head gasket was used on recommendation from the mechanic.

I cannot seem to hear the sound when in the engine bay and rev the engine.

I had a shop look at it they were inconclusive in their determination. Said i should adjust valves.

Engine runs very strong, temp is fine. I had managed to get it quieter via the snorkel and resonance on the intake.

They aren’t exactly quiet once the revs are up , is this just the level of noise or the kind of noise ?

Its pretty mild resonance with a slightly hollow tone which occurs only when the car is driving (at least I can't seem to hear it when standing above the engine bay and putting the engine in the corresponding rev range).

It occurs in the rev range corresponding to 65 through 70 kmh in fourth gear. Above and below this engine speed there is nothing abnromal.  Its a different tone than the engine note.

Again, the resonance is minor, most people only acknowledge it when I tell them to listen, its not something which creates an overpowering feeling of What the blithering heck. 

I will look over the vehicle again this week, I just wanted to reach out for some possible leads. 

 

I can see now why this is important to you - 70 kph is just 43 mph, so the general cacophony will not have reached terminal levels, it’s quite a relaxed pace.

What about removing the engine lid, and hanging over the back of the rear seat while someone drives (in a safe location, windows open for fumes) for more diagnostic listening?

wrap your whole inlet in pipe lagging.
Check your engine mounts

The problem ended up being the heat shield on the exhaust manifold. There are two pieces of metal, both were not well tightened. The problem one in my case was the rear one. 

So great to have that rattle gone.  

I do like a happy ending to a noise/rattle/squeek story, goodness knows we've got enough of them and its always good to investigate for peace of mind and to hopefully nip any issues in the bud.

Plus its good therapy to share on here, sometimes our partners/passengers don't understand the angst of how our minds work - is that rattle just a rattle, or the sign of impending doom? Or something even worse?

Glad you've persevered and sorted it; calm can prevail