need help just did compression check

[brs86supra]

Well as the title says i just did a compression check and the results are as followed.
Cylinder# Compression
1 150
2 140
3 150
4 140
5 between 135-140
6 140

so now im lost, so i think if i did have bhg it probably blown between 4 and 5? but now sure. Cause my car keeps overheating and i have already replaced the radiator cap and thermostat and it still overheats. so now i think im gonna drain the radiator and flush that old crappy thing. oh and by the way after letting the car sit overnight i can go start it and a little cloud of smoke does appear but only for a second and then it goes away. so if anyone could help me figure this out i would greatly appreciate it.

 

[Poodles]

Compression is a bit low...but fine going by how close they are together.

Functioning fan clutch?
Fan shroud?

Probably original radiator, replace it. Also, the smoke is probably valve stem seals...

 

[brs86supra]

clutch works and no fan shroud and original radiator. so i think i may swap it out with a brand new one i have laying around. but its for a rx7 so i may have to modify some stuff. and another thing im not sure if its bhg because a couple of years ago when i had it i had all the symptoms and this time i have none. but ill keep on looking and testing on the car adn see

 

[Poodles]

Fan doesn't function correctly without a fan shroud. It pulls the air from around the fan and not through the radiator.

Get a NEW radiator, don't rig one up as it won't work with the fan shroud, not to mention it might not have the compacity you need.

 

[IJ.]

135>150 is out of spec.

 

[92nsx]

TSRM shows compression for a 7mgte should be 142psi, with a max difference between cylinders of 14 psi and a minimum of 128 psi.

 

[Poodles]

He said between 135-140 so I assumed 137 and that would be in spec...not ideal, but in spec.

Could do a leakdown test and listen for bubbles at the radiator cap, but I doubt the HG is blown...

 

[brs86supra]

ok thanks a lot guys, now that i think about it i think i still have my radiator from my 86.5 n/a so i will try that. but i was looking at the specs for the supra radiator and i seen this:
Specifications:

* Dimensions: 14 3/4" x 25" x 1 1/4"
* Rows: 2
* Tank Inlet: 1 3/4" x 25 9/16"
* Tank Outlet: 1 3/4" x 25 9/16"
* Hose Inlet: 1 3/8"; Top Left
* Hose Outlet: 1 3/8"; Bottom Right
* TOC: 12 7/8"
* EOC:
* Construction: Plastic Tank Aluminum Core

What is TOC? and just for fun here is the specs for the rx7 radiator:

Specifications:

* Dimensions: 16 3/4" x 22 3/8" x 1 1/4"
* Rows: 2
* Tank Inlet: 1 3/4" x 22 3/8"
* Tank Outlet: 1 3/4" x 22 3/8"
* Hose Inlet: 1 1/2"; Top Right
* Hose Outlet: 1 1/2"; Bottom Right
* TOC: 9"
* EOC:
* Construction: Plastic Tank Copper Brass Core

so as poodles said i think i will try my spare supra radiator, cause i dont think the rx7 one is compatable

 

[Poodles]

Turbo and N/A radiators are the same, so you'll be fine as long as it's not clogged.

 

[buckshotglass]

I would still do a leak down test. Was the car warmed up for the compression test?

 

[92nsx]

I would still do a leak down test. Was the car warmed up for the compression test?

Good question, I missed that

 

[CRE]

The cylinders with 150 could have more carbon build up than the others too. When you did the HG did you clean your pistons? Did you test the compression with oil added to the cylinders and did you pull the EFI fuse when testing?

The stock radiator is fine as long as it's not cracked or kinked anywhere. If needed, most drivers need do nothing more than rebuild it and have it professionally flushed. Definitely get that fan shroud on and I'd recommend replacing the undercover if that's gone too.

 

[Poodles]

These days it's cheaper to just replace the radiator than have it rodded...

 

[CRE]

You're being presumptuous that there's anything even wrong with it. Most of these radiators that I've seen with issues usually only need a professional flush and new seals for the end tanks... MUCH cheaper than a new rad. It depends on how the car is going to be driven and who's doing the work of course.

 

[brs86supra]

The cylinders with 150 could have more carbon build up than the others too. When you did the HG did you clean your pistons? Did you test the compression with oil added to the cylinders and did you pull the EFI fuse when testing?

The stock radiator is fine as long as it's not cracked or kinked anywhere. If needed, most drivers need do nothing more than rebuild it and have it professionally flushed. Definitely get that fan shroud on and I'd recommend replacing the undercover if that's gone too.

when i last did the hg job, i did clean the pistons. And i didnt do a compression test with oil added to the cylinders yet, adn when i did it the first time i didnt pull the EFI Fuse, but should i have?

but so far i swapped over the radiator with my spare one adn its not overheating, but im gonna keep my fingers crossed.

 

[brs86supra]

oh and yes the car was warmed up when i did the first test.

 

[Poodles]

YES pull the EFI fuse so fuel isn't flowing.

You still need a shroud though, it makes a HUGE difference.

 

[brs86supra]

ok thanks for everyones help. i just need to find a fan shroud now