Timing Chain Question

[jschatz]

If a timing chain breaks or slips in a SOHC v6 will the motor still crank? Will the motor attempt to turn over and fire?

Thanks,
Ray

 

[2000StreetRod]

low compression on one bank

If either the left or right camshaft timing chain breaks then the camshaft will probably come to rest in a position with low valve spring pressure. Some valves on the bank with the broken chain may be partially depressed but it is unlikely that any valve will be fully depressed. As a result, there is a chance that the valves may not be struck by the pistons when the crankshaft is rotated. The compression on the bank will be extremely low (zero) and it is unlikely that the engine would start on only three functional cylinders.

If the crankshaft to jackshaft chain breaks then neither camshaft will rotate but the relationship between the two camshafts will be maintained because they are both connected to the jackshaft. Both banks will have low compression and the chances of the pistons striking the valves are greater when the crankshaft is rotated. The engine would not start with no functional cylinders.

The chains are much stronger and longer lasting than the guide assemblies and the tensioners. Common failures are broken left and right guide assemblies and the primary (crankshaft to jackshaft) tensioner. If a guide assembly failure results in a slipped timing chain then the camshaft continues to rotate when the crankshaft rotates and the valves continue to fully depress but at the wrong time. If the chain only slips one tooth the engine may still start and run. If the chain slips enough the valves (usually the exhaust) will be destroyed by being struck by the pistons. The primary chain only infrequently slips when the primary tensioner fails.

 

[waskly]

its a interference engine, will it crank possibly if the chain broke while driving, even during cranking, and bent valves.... it can possibly crank. most times tho since lack of clearance it will stop cranking at some point. once the open valve hits the piston.

 

[jschatz]

Thanks. I will add possibility to my no start situation. My 98 has has ~248k miles on it, major chain rattle on startup. It died on my father going down the road the other day. I have changed the fuel filter and I have ~38psi of fuel pressure. The start relay and fuse are good. The starter cranks. My coil pack is producing spark. I changed my crk position sensor today. The other morning after it was down to single digits it took a long time to start. I thought my fuel may have had issues so I added a bottle of heet. I also hooked up some jumper cables for some extra juice. I am running out of ideas as to why it will not start. Ideas?

 

[2000StreetRod]

compression check

A compression check of all cylinders will tell you if a timing chain has slipped.

 

[apuszczalowski]

I had this exact same issue last week, the motor lost all power and then stalled while driving. Pulled over into a parking lot and all it would do is crank, I thought it wasn't getting fuel cause it cranked without a problem, just what sounded like a little bit of a slapping noise.

Spoke to the mechanic Saturday and he says the rear timing chain looks like it jumped a tooth and its slapping against something inside

I'm still waiting to hear back on the cost to have the motor pulled to fix the timing and then to have it put back in to check to see if any valves are bent/broken.

Mine only had 154k KM's (96k miles on it)

 

[jschatz]

Checking the compression is a lost cause. I would have to pull the heads and re- thread the spark plug holes because they are stripped. All the plugs are seated but cannot be removed. It is a story for a different time. The decision was made last year when the plug issue occured the motor would be replaced when it needed spark plugs again or when an issue with the chains occurred. After having a couple friends look at it we have decided that something has slipped and the something is slapping inside. The motor would need a complete rebuild at this point with mileage to even be worth fixing.

A motor swap may be a better option or it may be off to the scrap yard. Is it possible to swap in a motor out of 96 sohc 2dr into my 98 2dr? I know the fuse box looks different but other than that I do not know the differences.

Thanks.

 

[2000StreetRod]

No 96 SOHC V6 in the U.S.

I believe the SOHC V6 was not produced for the U.S. market until 1997. I suspect the V6 in the 96 is a OHV instead of a SOHC. The SOHC V6 is a fairly expensive engine to rebuild. I agree that purchasing a used one from a salvage yard would probably be less expensive. Since you can't even change the spark plugs on your current engine it may be time to retire it. It is inexpensive to check the camshaft timing visually but takes a fair amount of work: SOHC V6 Timing Chain Inspection & Repair

 

[jschatz]

Oh maybe the parts truck I bought is a 97 then. The motor looks the same from the top and had the plastic cover thing that says 4.0 L SOHC so maybe it is a 97. It has been 6 or 7 months since I bought it. I do know that it is pre PATS and it does have a different style rear hatch. I just didnt know if everything was the same sensor wise so that it would hook up to my 98s wiring harness. Most likely if I can use this motor I will probably scrap both explorers and just cut my losses. There are not a whole lot of salvage yards in the area and the ones that are here are outrageously priced. If I am able to use the motor I have I will replace the guides for the chains while I have it out. I just dont know whether it will work and I am hoping someone here can tell me.

 

[2000StreetRod]

any Ford 4.0L SOHC V6

Actually, you can use any Ford 4.0L SOHC V6 as a replacement: Discovery III, Explorer, Mountaineer, Ranger and Mustang. Your 97 engine should be nearly identical to your 98 engine. There were fuel system changes sometime in 98 when Explorers went from a return fuel system to a returnless one. Check your 98 for a fuel return line to the tank from the fuel pressure regulator on the fuel rail.

 

[jschatz]

This may sound silly but if the front clip is removed can the engine and transmission be pulled as a set with a 2 ton crane?

 

[petzl90]

I am unsure about my timing chains. My engine has been making a strange noise at about 3k RPMs and up until the engine gets so loud I can no longer hear it (about 4k RPMs). Some people (who are not car people) said it sounds like the valves are clattering. Many oil changes, fuel filter changes, switching to 89 gas, and about 1.5 years later it still does it. We had it sent to a local mechanic (told him we think its the valves) and he said that he could find the problem. The thing is, the best way I can describe the sound is that of a chain being shook. Is it possible that a timing chain tensioner broke, which is causing the chain to rattle?

P.S. Its been doing this for almost 2 years with no problems.

 

[jschatz]

I almost have my parts truck motor out which I will be putting on a stand and going partially through. The motor in my truck is pretty much trashed so im not worried. I just want to know if I can pull the motor amd tranny out together if the front clip is off. The transfer case and driveshafts are both already taken out of the parts truck so It shouldn't be that hard to get the transmission out and I thought it might be just as easy to pull them out as one and then separate them.

 

[2000StreetRod]

remove the radiator

I believe at least one member posted on the forum that he had removed the engine and transmission as an assembly. If the radiator is removed then there is a lot more room to maneuver. However, the body may have to be higher in order for the transmission to clear the tunnel/bellhousing body opening. Also, the required boom lift will be greater.

 

[jschatz]

I intend to pick up a 2 ton crane tomorrow so I am not worried about boom restriction. They radiator is already out and I am thinking about pulling the front clip so I should be able to raise the body and then pull it out. If not I will separate it and then just pull the engine out. The tranny is trash anyways. I think the hardest part will be getting the engine hooked up onto the crane. I hope to get the parts truck engine out sometime soon, maybe by wednesday evening.

 

[2000StreetRod]

2 ton crane base width

I believe the base of a 2 ton crane is wider than the distance between the front spindles. With the vehicle lifted the A arms will be low and may interfere with moving the crane fore and aft. It may be necessary to raise the vehicle more for clearance. One reason I got 6 ton jack stands for Christmas is they have a maximum 24 inch height.

 

[jschatz]

I guess it is a good thing my parts truck is sitting on 6 ton jack stands all the way around. I picked them up a couple of weeks ago so I can put the transmission back in my brothers truck. But if I have to move to much side to side then I will have to move the parts truck over.

 

[tomj1102]

Where to go for Timing chain repairs in uk

Hi I have a timing chain noise at times especially at start up then quiet and only get a noise back when accelerating slightly harder than normal. I have decided to get the tensioners and chains changed. My question is where to go for the best price without a compromise on quality. I am also looking to find somewhere close to Cheltenham or Chipping Norton. Does anyone have any one they know of.
Cheers

 

[bobflood]

Hi I have a timing chain noise at times especially at start up then quiet and only get a noise back when accelerating slightly harder than normal. I have decided to get the tensioners and chains changed. My question is where to go for the best price without a compromise on quality. I am also looking to find somewhere close to Cheltenham or Chipping Norton. Does anyone have any one they know of.
Cheers

Might want to post this over in the UK section to make sure that folks who can help you see it. Good luck!!

 

[jschatz]

So I have everything stripped of and am ready to yank these suckers out. Where exactly am I supposed to bolt chains to the block at? Some pictures would be handy. And what thread pitch bolts do I need for said holes?

Thanks,
Ray