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CRV persistent rattle

My 1999 Honda CRV (80k miles) has a tinny-sounding rattle on acceleration after about 30 mph. It sounds like it’s coming from the heat/AC vents. Have noticed this problem the past 6 months.

Took it to the dealer where I have had the car serviced for 10 years and they told me the glove compartment was loose, charged me an arm and a leg to install a new screw, and reported the problem fixed (which, obviously, it was not). The car passed state inspection at the same time.

I am thinking it is a loose heat shield or something with the fan assembly…in our minds it seems to be worse when the heat or AC is running?

Are you sure that you are not hearing engine “ping”, rather than noise emanating from the HVAC system?

I can tell you from personal experience that Honda EGR valves can get gummed up fairly easily, and a gummed up EGR valve is the frequent source of engine pinging. Since persistent pinging can damage your valves, I would suggest that you have an independent mechanic explore the possibility that your engine is pinging.

There is also the possibility that you are hearing noise from a loose heat shield, so have your mechanic also check the exhaust system while he is checking the EGR and other possible causes of engine pinging. While a loose heat shield is not dangerous, it sure can be annoying.

<<Are you sure that you are not hearing engine “ping”, rather than noise emanating from the HVAC system?>>

Nope, I’m not sure of that at all. However my (now former) mechanics are certified Honda technicians, should they not have checked over the emissions-related valves during the state inspection?

I’ll second VDCdriver on the EGR recommendation.
As to whether they should have checked the EGR system that could be debateable.

If this problem does not occur, or is not near as prevalent, when the engine is cold and is worse when warmed up and under a load (uphill, passing, etc.) that is also an indicator the problem is EGR related.

“However my (now former) mechanics are certified Honda technicians, should they not have checked over the emissions-related valves during the state inspection?”

Whether they should have done this is determined to a great extent by the nature of your state inspection. However, I have never heard of an EGR valve being checked as a part of an emissions-related inspection unless perhaps there was a strong indication that it was malfunctioning.
I seriously doubt that the EGR was ever looked at.

It’s definitely worse when the car is warmed up. Thank you, I have a recommendation for a mechanic and will pursue this line of inquiry.

P.S. Have now done some googling and found that the older CRVs do indeed have valve problems. However the valves tend to tighten instead of loosen and some say therefore are not associated with a noise. That said I’ve read enough to worry that I have a possible valve problem perhaps unrelated to this annoying rattle.

You are confusing apples and oranges, so to speak. Both are fruits, but they are different fruits. In a similar vein, your car has different types of valves.

Your engine has intake and exhaust valves (that allow air/fuel to enter the cylinders, and that allow the products of combustion to be extracted from the cylinders), and an EGR valve. The intake and exhaust valves are what is being referred to in regard to valves that need adjusting, and this can indeed be a problem in terms of engine longevity.

The EGR valve (which is totally separate from the intake and exhaust valves) allows a portion of the engine’s exhaust to be sent back to the cylinders in order to improve emissions. When the EGR is stuck, the air/fuel mixture being sucked into the engine is too hot, and this hot mixture ignites unevenly. This uneven combustion is what is heard as “pinging” or “spark knock”, and it can lead to internal engine damage.

So, it would be a good idea to have the engine’s valve lash (intake and exhaust valves) checked and adjusted if necessary, and as ok4450 and I have suggested, a cleaning of the EGR valve may eliminate your rattling noise.

Overtight valves are far worse than loose ones as overly tight ones can cause burning of the valve faces and cylinder head valve seats; spelled expensive.
A loose valve can be differentiated because it will be most noticeable at idle.

The recommendation by Honda Motor Co. to inspect valve lash in excess of 100k miles is a very bad recommendation. Other car makers also make the same bone-headed recommendation; Subaru, Toyota, Nissan, and generally any car that uses a mechanical lifter instead of a hydraulic one. The car makers do this as part of an effort to make their cars appear to be more maintenance free. In a nutshell; PR at the expense of the car owner.

Your CRV has pretty low mileage for the age and there’s a good chance if the problem is EGR related it may be nothing more serious than clogged EGR passages.
The same thing occurs with EGR passages as what happens with the fireplace in a home. Ever so often it needs to be cleaned out and in the case of a car a can of SeaFoam admininistered through the intake manifold may do the trick.
The years of light duty driving have probably been the reason for clogged ports.

(To elaborate a bit further on how ridiculous the factory recommendations are on valve lash inspection you need look no further than statements like “have an audible inspection done”.

That is a statement that is not only asinine but flat blows me away because there is no way on Earth even the best of the best, totally knowledgeable, factory techs or engineers can determine what valve lash is by listening to it. The quiet valves are the ones you should worry about the most.)

although the other two replies are correct, they may have twisted you away from an obvious suggestion/solution.

the EGR valve is NOT the valve issue you found in the internet. what you found is a separate but important item.

and the heat shield should be mentioned to your mechanic to totally eliminate it from the possibilities.

you mention; “why didnt they look at all other possibilities.” well, it depends on what you said to them when you dropped it off. if you said the engine is making noise from the vents then they may not have even looked under the car at the heat shield.

and personally; at your vehicles age/mileage i would suspect the heat shield being about to fall off is a distinct possibility. (the noise they make is quite rattle(y) and annoying.)

good luck at your new mechanic.

You guys have helped a lot…had a talk with the new mechanic this morning and am taking it in on Wednesday, will report back. He seemed pretty up to date on the older CRVs as they had just had one in (with the tight valve problem). Now I understand that these valve issues are different things and will make sure to specifically mention the EGR valve. Thanks again

While the car is in the shop, also have him drain and replace the “Dual-Pump Fluid” in your center and rear differentials. This will help to avoid the “binding up” of the differential in slow speed turns, which is a chronic problem with CR-Vs. Make sure that he uses the genuine Honda fluid. It isn’t cheap, but the other brands of fluid are not compatible with Honda’s differential design.

Reporting back. Had the car into the new place this morning, the mechanic drove it to listen to the rattle, took it back to the shop and found a broken heat shield. He cut off the shield, showed it to me, charged me thirty bucks and said I’m good to go, the car itself is running well. (Didn’t replace the shield!)