Difficulty getting into 1st gear when hot (and when AC is on?)
 

This is on my 2003 Protege 5, manual transmission.

With the warm weather over the weekend I noticed when I am driving in traffic for prolonged periods of time with the A/C on it gets increasingly difficult to shift into 1st (and other gears get notchier) from a complete stand-still. Is there some sort of safety that prevents accidental downshift into first that may be acting up?

It was totally fine during the colder months, and fine in the evenings when it is cooler.

Some other things I've noticed:

• Slots into gear just fine immediately after engine is turned off
• After some highway driving it gets easier to shift into 1st again
• The A/C may or may not be causing or increasing the problem (I haven't done a real comparison yet)
• When rolling to a stop, it slots into 1st easily when at very low speeds just about to stop

Things I've done to try and stop this:

• Front engine mount (side engine mounts seem ok)
• Manual tranny fluid
• Lubed up shift linkages

I am ordering some aftermarket Corksport shifter bushings next, but I don't think that will make much difference.

Any ideas?

Does Mazda has a factory manual so that you can see if A/C even shares any connections eg cooling / hydraulic components with your gearbox? It might be your gear oil got burnt away causing overheat?

That's the general gripe I have agaginst Japanese cars are the lack of good thorough DIY manual (like Bentley equivalents).

You've got bad clutch hydraulics. The clutch disc isn't being fully disengaged and is keeping the transmission input shaft spinning with drag.

It's worse when your AC is on because the engine RPM is increased, so the synchros have to work harder to let you shift into first. It's easier when you're still rolling because your output shaft is closer to the speed of the input shaft.

Double clutch that bish

Hmm, I will try replacing the hydraulic fluid since it only seems to be an issue in hot weather and in traffic (i.e. more braking, hotter brake fluid).

Double clutching doesn't work :okay:

When he said "clutch hydraulics", he meant physical components besides the fluid. He's talking clutch slave or master cylinder. What's the mileage on your car?
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160k kms. I checked recently and there's no leaks from the system. Brakes and clutch feel fine, not spongy or anything.

Maybe the master cylinder is on its way out?

The thing that puzzles me is the fact it shifts perfectly fine when cold and only happens when hot; I would've thought a dying master or slave cylinder would have issues even when cold.

But I'll add it to the list to check and perhaps replace.

I forgot to mention and I don't know if this applies to your car but if I recall correctly, the symptom you're experiencing was a common case of the slave cylinder on E30s and E36s slowly giving out as well.

Again, I know you have a Mazda but just throwing a suggestion out.

well when your system heats up your clutch fluid could heat up and therefore be thinning out, which would cause your clutch master/slave to have a harder time engaging/disengaging

Also recall that as things warm up, they expand.

What brand of transmission fluid do you run?

I am using Quaker State Synchromesh in there currently; had the same issue prior to the change, though.

Did some more digging and read some threads saying it could be as simple as needing a clutch pedal adjustment, so will give that a shot first.

I have trouble putting it in reverse and occasionally first when the ac is on and the car is cold.

had this problem on my old prelude. eventually got worse and worse. it was the master cylinder

For the record, I've had nothing but problems with the slave cylinder in my old Mazda's. Luckily they were super easy to replace and relatively cheap, but it appeared to be a common problem for a few years with Mazda cars.

Edit: And if my thinking is correct, the Protege5 engine is basically still the same as the ones from the mid-late 90's (just updated here and there). So that could very well be the problem.

I would have started with the cheapest and most probable cause by flushing the fluid from your master and slave and bleed it out fully. Its most likely the original dot 3 fluid in there and will absorb moisture over time. What this does is the moisture turns to small pockets of water vapor in the system that will compress when you press your clutch pedal and by doing so wont creat enough force to fully extend the slave. This is also why old brakes feel spongy when they are hot. Your AC is making it worst because it increases underhood temperatures.

I've had the same problem on my mitsubishi eclipse. In my case it was the slave cylinder, I tried changing fluid and checked for leaks but nothing, eventually I pulled the dust boot off the slave and saw that it was leaking. I replaced it and my car shifts smoothly regardless of whether it's hot or cold.
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