rx7nerd

my 7, when i got it, was sitting around for 6 months ,i'm thinking the seals in the engine possibly dried out(thats what everyone is saying,if thats even possible) but i have spark,i have fuel, and i'm guessing i got low compression,what type of oil should i use to gain back compression? i was thinking 20w-50...but then again tranmission fluid works too...any suggestions

hhn2002

really no sure fire way to gain back compression other than rebuild. how are u sure you've got low compression? your right in being skeptical about seals drying out cuz they cant.20-50 is a good choice to combat fuel dilution. look up fuel dilution if you dont know what that is.

Snack

the seals could have seized down because of built up carbon. carbon + time = glue. if u pour some tcw3 two cycle into each face of the rotors, it will build up some compression. a good way to see if theres compression is the poor man ways. pull the trailing sparks plugs out of the motor, pull the egi fuse out(no flooding) and crank the motor. if it has a constent choo choo train sound without any pause, you have no seized of broken seals.

SpeedOfLife

iTrader: (16)

No, everyone is not saying that, and no one who is should touch a rotary (unless they just say 'dry' as in 'devoid of oil', but that usually isn't the case). The seals concerned with making compression in the motor are all metal, and they do not expand nor contract with the lack of or presence of oil. Now, low compression can be caused simply be wear, stuck seals, blown seals, poor sealing surfaces (housings/irons), too thick of motor oil, flooding (the gas washes the oil off the sealing surfaces. in severe flooding cases, it may be necessary to put just a few ounces of two stroke oil into the combustion chambers through the leading (lower) spark plug holes to regain that oil seal.), or maybe your starter isn't turning the motor fast enough. There may be a few cause I missed. That's just a quick overview, but reading the FAQ and searching the forum (using the search feature) should give you what you need and more.

rx7nerd

heres the whole story of why i am suspecting low compression
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/problem-13b-engine-718674/

SpeedOfLife

iTrader: (16)

Search compression check. A suitable compression gauge can be had for about $25 and checking the compression is not very difficult, but will probably require two people to do.

Hecubus84

iTrader: (1)

You need to stop suspecting low compression and start checking for low compression. Go to autozone and buy a cheapie compression tester, remove it's one-way valve and go to town.

Sideways7

iTrader: (7)

Actually, if a motor sits without being properly stored, the seals can "dry out" for lack of a better term. This is the exact reason why j-spec engines should be rebuilt before you put them in your car. 6 months, however, probably isn't long enough to do much if any damage.
That said, anyone that said that causes low compression IS an idiot. Low compression comes from worn out housings and hard seals, usually a combination.
Just do a compression check (directions in 2nd gen FAQ) and see what your compression is like. If its bad, the only way to fix is a rebuild.

rx7nerd

ok thanks

rx7nerd

i got 10-40 will that work to gain back some compression?

Hecubus84

iTrader: (1)

I assume you mean 10 psi on the front and 40 psi on the rear, those numbers mean your engine is likely done. It's highly unlikely you can increase your compression to 80 psi (bare minimum for an engine to run properly imo).

You will either need to have you engine rebuilt or find a used core with good compression.

Sideways7

iTrader: (7)

No, I think he's talking about 10w-40 motor oil and asking if it will help him with compression.

So the original poster: Have you checked for compression yet? If not, go do it now before you post again. And to answer your question, no that won't give you compression. The ATF trick is only to gain INITIAL compression after the engine has been flooded, not to gain overall compression. As we have said, nothing but a rebuild will get you more compression if the motor is shot.
Now if you do have low compression, it could be from sitting. I dropped in an engine that had been sitting for over a year and it had awful compression - about 70-75 PSI on each face. After I got it running, it eventually came up to about 95-100 PSI on each face.

Remember, the main thing you are looking for with the compression check is even pulses. As long as all of the pulses are even and the compression is at least decent, you should be ok.

Hecubus84

iTrader: (1)

To the op:

Ditto with sideways. Compression test your engine. We really can't diagnose what's wrong with your car until you supply us with this, the most basic of information.

Hwn_RX7

time for a rebuild

rx7nerd

ok,so pull the the lower plugs and roll it over and check if there are even pulses (or) get a compression guage and check it normally,.

(oil question) so your saying the 10w-40 is not going to help gain any compression back?

Hecubus84

iTrader: (1)

Use the top plugs, using the lowers will yield a slightly lower compression rating. Hopefully you will get 3 even puffs of at least 80psi on both rotors. Ive seen engines run on less but the all had to be bump started and/or had hot-start issues..

Yes, motor oil, soaked in the engine can help increase your compression but only on certain circumstances. For instance if your seals are locked up with carbon.

rx7nerd

ok great...i put the motor oil in the top plugs,rolled it over a few times and left it for a while, came back out with a fully charged battery and rolled it over but still did not start,so i pulled the plugs and i figured out that the oil got all over the plugs and it wasnt starting so i took the plugs dried them out and now i am waiting for better weather