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Several months back, I was having issues with my 2001 CR-V running really rough, to the point of being undriveable. I ended up having the distributor replaced, and it seemed okay. A friend who checked it out before I had it fixed said it might be a vacuum leak, but those were hard to track down. (Keep in mind, I am not super mechanical. I can learn, but I'm not really set up here to do a whole lot of getting up under the car to check things out.) I also had the transmission rebuilt in November 2018, about 30,000 miles ago, give or take.

What I'm noticing currently (and these things may or may not be related, I don't know):

When the car is idling, it occasionally tends to run hot. Scary hot. The first time it happened, I was in slow moving traffic on a fairly hot day. Turned the heat on, temp dropped, traffic started moving, everything was fine. I hadn't noticed it since then, but last night it happened sitting in a drive-thru line waiting to pick up our order on a not terribly hot evening. Temp dropped with the heat on, but the engine was ticking, so I pulled over, sat a bit, and let it cool. Cranked it up, made it home just fine. The coolant level seems okay.

Occasionally the car hesitates when accelerating - sometimes it's from idling in park, sometimes it's from idling in gear, sometimes it's from going from reverse to drive and accelerating. From what I've read, this could be a symptom of a vacuum leak. It could also be something transmission related, and maybe I should get it checked out before that two-year warranty on the rebuild expires. (Of course, I'm not sure what they could check other than fluid level - when it was rebuilt, the shop told me that with this generation of CR-V, it's a closed system, and you can't really do anything with it without taking the whole thing apart anyway.)

Fast idle. Per specs, my CR-V should be idling at about 750 RPM on startup. It normally idles around 1000-1250 RPM on startup. I understand high idle could be a sign of a vacuum leak.

I don't notice anything leaking from anywhere under the car. Generally, once we're rolling, Thunderhorse is good to go. He's a good little car, and I hope to keep him in good order for a couple more years. Any thoughts on these odds and ends? Thanks for any insight!
 

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When the car is idling, it occasionally tends to run hot. Scary hot.
You have one and/or two problems: an air bubble in the cooling system, or a defective thermostat. It being almost 20 years old, maybe a new thermostat is in order 'just because'.

Fast idle. Per specs, my CR-V should be idling at about 750 RPM on startup. It normally idles around 1000-1250 RPM on startup. I understand high idle could be a sign of a vacuum leak.
Yes it can be. With the engine running, listen for any hissing. Does the under-hood sticker indicate anything about vacuum hose routing?
 

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A vacuum leak is simple to find by using a smoke test. A machine pumps smoke into the vacuum system, and a leak will be detected where smoke is seen exiting the system. A good shop will have one. I don't know if the auto parts stores loan these out or not.
 

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Vacuum leaks can be found fairly easily by spraying oxygen sensor safe carburetor cleaner sparingly along vacuum lines, valves and intake manifold to cylinder head. DO NOT SPRAY ON IGNITION WIRES! If wires are leaking voltage you could have ignition. If you find leak the idle will slow and smooth out. As noted before by someone else, they can sometimes be found by a hissing noise. Additionally, the engine on start up will idle higher until thermo wax valve heats and lowers a controlled vacuum leak. On over heating, must confirm the engine is overheating first. Using a laser sighted sensor or otherwise. You can listen for cooling fans, are they coming on? If they are not, check system by jumping fan control switch plug at back of thermostat housing with paperclip and seeing if fans come on.
 

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Discussion Starter #5
You have one and/or two problems: an air bubble in the cooling system, or a defective thermostat. It being almost 20 years old, maybe a new thermostat is in order 'just because'.
I went back and checked the list of things done to my CR-V before I got it in August 2018. The thermostat has been replaced, probably in the last 30,000 miles or so. So the one in there isn't as old as the car.



Yes it can be. With the engine running, listen for any hissing. Does the under-hood sticker indicate anything about vacuum hose routing?
I'll look and see. I don't hear any hissing with the engine running. I do hear a kind of teakettle whistling noise once I get up to about 40 miles per hour, and the faster I go the higher pitched it gets until I no longer hear it. I've noticed that since I've had the car, though. I thought that was just wind noise.
 

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A vacuum leak is simple to find by using a smoke test. A machine pumps smoke into the vacuum system, and a leak will be detected where smoke is seen exiting the system. A good shop will have one. I don't know if the auto parts stores loan these out or not.
I've got a friend who has that machine. I'm reasonably sure he'd bring it by if I asked. He and I have discussed the possibility of a vacuum leak before.
 

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Vacuum leaks can be found fairly easily by spraying oxygen sensor safe carburetor cleaner sparingly along vacuum lines, valves and intake manifold to cylinder head. DO NOT SPRAY ON IGNITION WIRES! If wires are leaking voltage you could have ignition. If you find leak the idle will slow and smooth out. As noted before by someone else, they can sometimes be found by a hissing noise. Additionally, the engine on start up will idle higher until thermo wax valve heats and lowers a controlled vacuum leak. On over heating, must confirm the engine is overheating first. Using a laser sighted sensor or otherwise. You can listen for cooling fans, are they coming on? If they are not, check system by jumping fan control switch plug at back of thermostat housing with paperclip and seeing if fans come on.
I do hear the cooling fans kicking on.

My husband took a look at the coolant. The radiator was full, but the coolant level in the radiator reserve was below the minimum line. He added coolant, and it's been fine since. Now, I haven't tested it by sitting in traffic. But it's been running a bit cooler than it was. I'll be going back to work next week, and I'm sure I'll have a chance to sit in at least a little bit of traffic. If it's still running extremely hot in those situations, then I'll try some of the things you suggested, Nebby.
 

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I do hear the cooling fans kicking on.

My husband took a look at the coolant. The radiator was full, but the coolant level in the radiator reserve was below the minimum line. He added coolant, and it's been fine since. Now, I haven't tested it by sitting in traffic. But it's been running a bit cooler than it was. I'll be going back to work next week, and I'm sure I'll have a chance to sit in at least a little bit of traffic. If it's still running extremely hot in those situations, then I'll try some of the things you suggested, Nebby.
No worries, just remember the fans. If you get hot with no fans you must start there by jumping the fan switch plug on the back side of thermostat housing. If the fans come on with the key, replace the fan switch with factory Honda only.
 

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No worries, just remember the fans. If you get hot with no fans you must start there by jumping the fan switch plug on the back side of thermostat housing. If the fans come on with the key, replace the fan switch with factory Honda only.
Good to know - thank you!

Just for the record, I had the opportunity to sit in a drive-through line this evening, the situation in which it ran so very hot recently. Temp stayed even, no overheating. Perhaps the added coolant was all it needed. I'll keep an eye on it for now and take steps should it start acting up again.
 

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Just some food for thoughts. That missing coolant leaked somewhere. I've lost head gaskets the same way. And both were things I could had avoided given propper attention.
The problem was the same in both cases.
There are small water hoses running from the thermostat housing by pass to the throttle body to fitv(crx) back to intake manifold. They are about 1/4" fuel line size to 3/8" cant recall. I used fuel lines to replaced them.
Check them out. they will spring a hairline leak. That's the cause for a low coolant at reservoir but full radiator. Once the radiator gets low there goes the head gasket.
 
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