Transmission stop leak products bad? - Toyota Nation Forum : Toyota Car and Truck Forums

evanak · 02-01-2010, 02:40 AM

I have a 1990 4afe sedan with about 195k on it. A couple months ago I thought my transmission was leaking gear oil. I was hearing a loud grating noise and when I looked under the vehicle (I was in a dark parking garage) saw what appeared to be a pool of oil, also saw constant dripping, felt the pool with my hand and it was oil. So here I am in this dark garage and I'm thinking my transmission front seal is leaking massive amounts, when in fact I pulled into the one spot in the garage where some other car had leaked allot of oil lol.

I went to the auto parts store and bought some transmission stop leak and extra gear oil, jacked up the car in the garage and added the stop leak as well as some additional gear oil. My goal was just to get the car home without blowing the tranny. Well I added the stop leak and started to add gear oil but the gear oil started to pour out which indicated that the fluid was full. Upon getting the vehicle home and going out the next morning I saw another big pool on the ground which turned out to be coolant, then it hit me, my transmission was fine but my water pump had went out.

I've heard that these stop leak products are detrimental to seals etc and can actually cause leaks, is there any truth to this? Especially considering my transmission is fine and was not leaking? Is this more of a concern with newer cars that don’t have many miles racked up? If I should be concerned is there anything that I should do like change the tranny fluid/ have a shop flush it?

Donald · 02-01-2010, 12:34 PM

The only transmission additive I have ever used is Lucas Transmission Conditioner, and was very pleased with the improvement it made.

If you have doubts about that stuff that you put in, maybe you should do a drain and refill every few days, about three times total. That should get enough of the old stuff out for it to not be that much of a problem.

But really, I wouldn't worry about it. I can't think of why would it damage the seals if it is supposed to be a stop leak.
I think those stop leak products usually soften up old seals and reduce their brittleness.

Just my uninformed opinion, lets see what others have to say.

blb · 02-01-2010, 01:06 PM

I positively can't understand how a person can mistake gear oil, for antifreeze, especially when the transmission is on the oppostie side of the car from the water pump. Did you dip your finger in the puddle to feel and smell the fluid to identify it? Anyway, back to the question at hand, the stop leak products are supposed to work by causing the seals to swell, whch they do. Over time, in the long run, the same ingredient used to cause the seal to swell, will also cause the seal to degrade. You can get the same effect by adding a cap full or two of brake fluid. If it was me, I'd probably just change the gear oil in the trans (probably due anyway) to get rid of most of the stop leak product and be done with it. Good luck with the water pump job.

***SCT*** · 02-01-2010, 02:34 PM

Yea, some additives are to swell rubber gaskets so they can seal. Anything like STOP LEAKs should be used temporarily until you can get the fix done. If a trans do leak a large puddle, STOP LEAK would not be enough to seal off such a big breach.

I've had customers where they think putting a thicker grade oil would fix a severely abused motor thats knocking itself to complete death. If an additive seals a leak, it's going to seal anything else it can too including things that's not suppose to be completely sealed.

Can't figure out how you can mistake antifreeze with trans gear oil either. Gear oil smells like almost like rotten eggs and is oily. Antifreeze is more of a water that dries sticky with a scent not as potent.

When you go to change your water pump, I SUGGEST you change the timing belt, timing belt tensioner, and the front crank oil seal as well. They have to come off anyways, and the oil seal is only a step more. Everything mentioned is a bitch to change, so change them all in one time than in four different times.

Donald · 02-02-2010, 12:07 PM

I can understand all too well how one can mistake fluids, having done it myself.
A little bit of haste and preconception can take you a long way down the wrong road.

toyotaspeed90 · 02-02-2010, 02:41 PM

Quote:

Originally Posted by SCT

Yea, some additives are to swell rubber gaskets so they can seal. Anything like STOP LEAKs should be used temporarily until you can get the fix done. If a trans do leak a large puddle, STOP LEAK would not be enough to seal off such a big breach.

I've had customers where they think putting a thicker grade oil would fix a severely abused motor thats knocking itself to complete death. If an additive seals a leak, it's going to seal anything else it can too including things that's not suppose to be completely sealed.

Can't figure out how you can mistake antifreeze with trans gear oil either. Gear oil smells like almost like rotten eggs and is oily. Antifreeze is more of a water that dries sticky with a scent not as potent.

When you go to change your water pump, I SUGGEST you change the timing belt, timing belt tensioner, and the front crank oil seal as well. They have to come off anyways, and the oil seal is only a step more. Everything mentioned is a bitch to change, so change them all in one time than in four different times.

first few are put well.... keep in mind when you seal something up... it doesn't know where the problem is.... so, it seals everything it can reach.... (this is the case for any kind of "stop leak" sealant... oil, coolant, trans (auto or manual), etc.)

the timing belt doesn't have to come off to change the pump.... makes it a bit easier.... the timing covers at least do, however.

evanak · 02-02-2010, 03:38 PM

Thank you Donald, in response to how did I mistake fluids.... I said in my original post that there was a puddle of oil already on the ground (discovered this later on) so when I put my hand down in a dark parking garage mind you.... I was in fact feeling OIL and seeing dripping (which yes turned out to be coolant) into that puddle if that makes any sense. My engine oil was full so based upon the location of the puddle of oil the only thing I could think of was the transmission. Oh and I already got the water pump changed out a week or so ago.