alankenji_84

I just bought a 4runner and it is now limping around so I ran a compression check and 2 cylinders out of 6 were dead. no compression at all. I am assuming that this is a burned valve problem. I was just wondering how I can tell if it is an intake or exhaust valve that in burned, or if that is really the problem. I need this car runnign good soon as I have to sell my truck and will be down to one mode of transport. any ideas would be greatly appreciated.

alankenji_84

sorry, but anyone have any ideas?

midiwall

Speaking from personal experience (ARGH!) but there's no _real_ way to tell short of pulling the head.

You should do a leakdown test (search if that's not familiar to you). One thing that can quickly be done to give you a hint is a simple paper towel test.

Take a single sheet and hold it at the end of the tail pipe while the engine's running (idle is fine). If the towel seems to get sucked towards the pipe, then you have a stuck/burnt exhaust valve.

Bottom line though, the fix is generally same for either intake or exhaust - you have to pull the head.


Obviously this is a 6 banger, is this the 3.0 or 3.4? There's nothing in your sig or profile to help figure that out. (hint!)

alankenji_84

Hey, thanks midiwall. I'll try to get my sig profile updated asap. its the 3.0what if the paper towel gets blown out with the exhaust? does that tell me it might not be a burned valve, and if so, any other ideas.

I might just go ahead and tear it down tomorrow. also, sorry for all the questions, but how do I know if I need the heads to be machined, and what all parts do I need.

Valves
Guides
Seats
anything else?

Thanks again in advance. This forum is such an awsome resource.

alankenji_84

sorry again, but any ideas about how much this valve job might set me back if I do it myself/ if I send it to a shop.

midiwall

Well, the paper towel test will only tell you if it's an exhaust valve - if one is stuck open, then there will be a vacuum at the tail pipe on what should be the intake stroke, and that's what will suck the towel in towards the pipe.

Given that you know you're losing compression, then you're looking at (in no particular order):

• Exhaust valve
• Intake valve
• Rings
• Burned piston
• Head gasket

Basically, if you pull the head and find a burned valve, then the RIGHT thing to do is to have the head machined. If this is the first time the head's been off, then there will be all sorts of crap on it and it needs to be cleared out.

If you've been running with a burned valve for a while, then you may need the cylinders honed... And, of course you may need a valve or two replaced.


If you do it yourself, and you have access to a milling machine (or you elect to NOT do the heads) then you're basically looking at the cost of the valves and a gasket set. Figure $300 total if you stay away from Toyota's gasket sets. If you send it out, then there's some decent labor involved, and figure on at least $100/hour.

For your "scary enjoyment", lemme point you here:
https://www.yotatech.com/forums/f123/3-4-rebuild-100924/

Now, I'm not giving $$$ numbers there, but I can tell you that the cost will go up dramatically based on how far you want to strip down the engine on your own. i.e., walking into a machine shop with a head and saying "do this" is a LOT cheaper than pulling the truck into a shop, saying "I need a valve job" and then walking out.

InternetRoadkill

If you know someone with a bore scope, you might be able to see what's going on thru the spark plug hole. The sad reality is that you're probably going to have to pull the heads to see what happened.

alankenji_84

HEy thanks, I was just wondering, How do I know which valves (intake/exhaust) are shot or if its pistons/rings etc. will a leak down before i take the heads off tell me more specifically. Thanks

midiwall

Yes. You really should search the forum, there's been a lot of talk lately about leakdown tests

This will get you started:
http://www.geocities.com/dsmgrrrl/FAQs/leakdown.htm

But understand that you already know you have 2 bad cylinders, so the heads are coming off. If you're trying to line up parts so you can have "everything you need" when you pull the heads, just over-buy. Pick up two sets of intake and exhaust valves along with a gasket set. But figure on forgetting something... you _will_ have to do a parts run or two while the truck is torn down in the driveway.

Also, like I said above, it may NOT be a valve... it could be rings, piston, etc...

Short of doing the work IN a parts depot, there's really no way that you're gonna get around tearing down the block and being without the truck for a while.

InternetRoadkill

The only thing that could be responsible for no compression that doesn't require removal of the head is a stuck valve. You can check for that by removing the valve cover and looking to see that the valve clearance is within reason.

WillRadford

How many miles are on your rig? It seems like almost every 3.0 needs a valve job around 170k - 200k. I just took the heads of a '91 I bought and it cost me $320 to have them cleaned up, have all the valves reground and have the bottoms remachined. I spent $140 on the gasket set. So you might spend ~$500 on the whole deal. Its not too bad to do it yourself. How much will a garage charge you for a valve job?

Does anyone at what point in a 3.0's life the piston rings or crankshaft bearings start going bad?

photomike72

engnbldr.com gasket set fer sure.

Just got mine back from another top-end rebuild on Friday.

good luck.

alankenji_84

If i get the heads resurfaced its $90. Valves bored $220 and another $90 to adjust them, plus $90 for the pressure testing. Total comes to $490 for the valve job befpre parts. is that a decent deal? also is there any way I can maybe do the adjusting myself.

I was also looking @ engnbldrs site and I didn't see a gasket set for a 3.0. does he still sell them? I did see he has valve sets for like $62, but how do I know what size I need. Does that depend on how much the vlaves need to be bored out.

Thanks for all the help. I am going to remove the head tomorrow and see what needs to be done

bwhyit

A vacuum gauge is the best way to check for burnt valves. Hook up the gauge to intake vacuum and wantch the needle. If the needle bounces around more than a 2-3 inches HG then you probably have a burnt valve.
My other question is: are the 2 low compression cylinders next to each other. If so then I would lean towards a HG or head problem.

alankenji_84

Thanks. The two dead cylinders are the middle cylinders on each head, and they don't have low pressure, there is no pressure at all. The needle doesn't even move. Does it matter which vacuum hose I use, or can I use any one. Thanks for the tip. I was looking for something that could tell me if it was the valves or if it might be something else.