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Discussion Starter #1
I've noticed the range rover has been down on power recently and as I was doing some work on it anyway I thought i'd do a compression test just to rule out any issues with piston rings, valves, headgasket, etc. On the compression test I got very low readings of 45 psi in 2 pairs of adjacent cylinders, Nos 8 & 6 and 3 & 1. The other 4 were all at 140psi

I guess this strongly suggests a headgasket but I find it really surprising as there are none of the other usual signs of a headgasket going, no coolant loss, no water in the oil, it runs cool, and there are no issues starting or idling. Can anyone suggest anything else that could cause the low compression in the adjacent cylinders??

I don't mind changing the head gaskets but want to be fairly sure before I do it and the lack of other symptoms is a bit if a head scratcher!!

Thanks, Simon
 

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SimonB said:
I've noticed the range rover has been down on power recently and as I was doing some work on it anyway I thought i'd do a compression test just to rule out any issues with piston rings, valves, headgasket, etc. On the compression test I got very low readings of 45 psi in 2 pairs of adjacent cylinders, Nos 8 & 6 and 3 & 1. The other 4 were all at 140psi

I guess this strongly suggests a headgasket but I find it really surprising as there are none of the other usual signs of a headgasket going, no coolant loss, no water in the oil, it runs cool, and there are no issues starting or idling. Can anyone suggest anything else that could cause the low compression in the adjacent cylinders??

I don't mind changing the head gaskets but want to be fairly sure before I do it and the lack of other symptoms is a bit if a head scratcher!!

Thanks, Simon
Any coolant loss, etc, is only really associated to a blown gasket in the rear cylinders between the cylinder and the water channel from the block to the head. No other cylinders have water galleries close to have an affect on coolant. I recently stripped down a motor that had low compression in two cylinders either side and it was a head gasket. But can also be a worn cam.

Put a Vacuum gauge on it and it should tell you more
 

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Discussion Starter #3
Thanks for the advise Ian. It was the headgasket, I stripped the engine down yesterday and found a 5mm wide hole through the gasket between 2 pairs of cylinders on each side.

Seems like the Engine has had the gasket changed before and at that point it was swapped to a composite gasket but whoever did the work made a right mess of torquing the cylinder head bolts up as some were practically loose, i'm surprised the car ran as well as it did. Because of this i think i'll now have to get the heads checked to make sure they haven't warped.

Anyway, hopefully new headgaskets combined with a set of reconditioned injectors will mean that all my running problems are over..... for this week anyway!!
 

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SimonB said:
Thanks for the advise Ian. It was the headgasket, I stripped the engine down yesterday and found a 5mm wide hole through the gasket between 2 pairs of cylinders on each side.

Seems like the Engine has had the gasket changed before and at that point it was swapped to a composite gasket but whoever did the work made a right mess of torquing the cylinder head bolts up as some were practically loose, i'm surprised the car ran as well as it did. Because of this i think i'll now have to get the heads checked to make sure they haven't warped.

Anyway, hopefully new headgaskets combined with a set of reconditioned injectors will mean that all my running problems are over..... for this week anyway!!
There must be something to this lose head bolt business. The head that I pulled with the back two cylinders leaking also had a couple of head bolts that were basically finger tight where the leak was, but it had full metal gaskets. I wonder what causes the head bolts to come lose.
 

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Good job on the find. I'm about to tear into my rover's heads as well, and was curious who carries the best composite kit for the price? Scott on my thread mentioning getting the 4.0 head gasket kit too, will that match up with my 3.9 pretty easily? Thanks in advance!

Zach
 

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ZLandrum said:
Good job on the find. I'm about to tear into my rover's heads as well, and was curious who carries the best composite kit for the price? Scott on my thread mentioning getting the 4.0 head gasket kit too, will that match up with my 3.9 pretty easily? Thanks in advance!

Zach
If it is your 89 that you are doing, they had metal head gaskets, not composite. Therefore you should not use composite when doing them.
 

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Not use composite head gaskets? That is the first time I've heard that advice. My '89 had a minor coolant leak from one of its head gaskets, so I disassembled it last winter. Some previous owner had already converted it over to composite gaskets. I bought a steel gasket kit before taking the engine apart, but then I researched and found many, many posts here and on other sites all recommending newer composite head gaskets for the 3.9. I bought a new composite head gasket set for my engine and it is working very well.

Please, what is the problem with using the composite gaskets on an '89?

Scott
 

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skucera said:
Not use composite head gaskets? That is the first time I've heard that advice. My '89 had a minor coolant leak from one of its head gaskets, so I disassembled it last winter. Some previous owner had already converted it over to composite gaskets. I bought a steel gasket kit before taking the engine apart, but then I researched and found many, many posts here and on other sites all recommending newer composite head gaskets for the 3.9. I bought a new composite head gasket set for my engine and it is working very well.

Please, what is the problem with using the composite gaskets on an '89?

Scott
Simple, they lower the compression ratio by around 10% to 15%. Composite gaskets should only be used with heads that only have 10 head bolt holes. Any head with 14 bolt holes should use metal gaskets. If you want to use composite on a 14 bolt head, have it machined down 40 thou.
 

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Ah, here is the possible disconnect. My '89 3.9 does have only ten bolts per head. The composite gaskets aren't that much thicker either, certainly not enough to lower compression 10%. However, the idea that I might gain a few percentage points of compression with the steel gaskets does appeal to me.... Hmmm.... I've still got that set hanging on a peg on the garage wall.... Still, the used composite gaskets that came out are 1.50 mm thick (less than the news ones that went in, I imagine), but they are slightly thicker than the stamped ridges on the new steel gaskets, which are 1.24 mm thick. These stamped steel gaskets are suitable only for heads with ten bolts too. (Curious that Buick used 14 bolts and Olds used 18 bolts on these same heads.)

Scott
 

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skucera said:
Ah, here is the possible disconnect. My '89 3.9 does have only ten bolts per head. The composite gaskets aren't that much thicker either, certainly not enough to lower compression 10%. However, the idea that I might gain a few percentage points of compression with the steel gaskets does appeal to me.... Hmmm.... I've still got that set hanging on a peg on the garage wall.... Still, the used composite gaskets that came out are 1.50 mm thick (less than the news ones that went in, I imagine), but they are slightly thicker than the stamped ridges on the new steel gaskets, which are 1.24 mm thick. These stamped steel gaskets are suitable only for heads with ten bolts too. (Curious that Buick used 14 bolts and Olds used 18 bolts on these same heads.)

Scott
An 89 would have come with 14 bolt heads, the 10 bolt heads were not made until late 94. Some people only fitted 10 bolts to 14 bolt heads, but they are still 14 bolt heads.

A composite gasket is 30 thou thicker than metal ones. The difference is 8CC. this can be verified by checking the chamber capacity of the 10 bolt heads to 14 bolt heads, it changes from 32cc to 24cc. Depending on the size of the motor and the compression ratio, the bowl size on the piston can change, but generally are under 20cc. So total capacity of a 14 bolt head and piston is around 50cc. Fitting a composite gasket will increase this by 8cc. As it is this capacity that is used to calculate the compression ratio, a 10% change in total size will change the compression ratio by 10%. That is, a 10% change to a 9:1 compression ratio would become 8.1:1. However, a 8cc increase to a 50cc chamber is not a 10% increase, but a 16% increase. So it drops the compression ratio by 16%

To counteract the impact of the composite gaskets, Land Rover shaved 40thou of the heads (head chamber is smaller diameter that bore and therefore a 30 thou change in bore length required 40 thou off heads to match capacities.) Again this is a documented spec and can be checked from a number of sources you can easily find.

As Land Rover has built the same motor in a high compression and low compression version, the difference in power is again well documented. If you fit a composite gasket to a low compression motor it will not run overly well, do it to a high compression version and the motor is still quite driveable, just down a bit in power.

So what I am attempting to explain is that the impact on compression ratios of using a composite compared to metal gasket is well documented, you just have to join a few dots together. The impact on power of decreases in compression ratio are also well documented.
 

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Discussion Starter #11
I'd second Ian's comments, I'm fitting composite gaskets to my 95 which has the old 14 bolt engine as the previous owner had already done that, and I didn't want to risk changing things. You lose a bit of compression and hence power but i'm not too worried about that.

You can tell the 2 different types of Engine by the engine number, Suffix A has metal and 14 bolts, Suffix B has composite and 10 bolts.

One further question from me regarding skimming the heads......... I've cleaned up both heads on my rangie and they seem immaculate, no scorch marks or other visible damage. Is it still worth getting them skimmed??? especially given that I'm using a composite gasket that theoretically has a bit more tolerance to defects than metal.

Cheers, Simon
 

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SimonB said:
I'd second Ian's comments, I'm fitting composite gaskets to my 95 which has the old 14 bolt engine as the previous owner had already done that, and I didn't want to risk changing things. You lose a bit of compression and hence power but i'm not too worried about that.

You can tell the 2 different types of Engine by the engine number, Suffix A has metal and 14 bolts, Suffix B has composite and 10 bolts.

One further question from me regarding skimming the heads......... I've cleaned up both heads on my rangie and they seem immaculate, no scorch marks or other visible damage. Is it still worth getting them skimmed??? especially given that I'm using a composite gasket that theoretically has a bit more tolerance to defects than metal.

Cheers, Simon
The block did not change with the move to composite gaskets. You can fit a 10 bolt head to a 14 bolt block without any issues. I had a 10 bolt block fitted with 14 bolt heads and composite gaskets. It was a 4.6 low compression motor and was always a little disappointed with the power. I later changed the heads to 10 bolt ones and the increase in power was very noticeable. It is now a very nice motor. So from first hand experience I can attest to the implications of using incorrect head gaskets. I will never fit the incorrect gasket to heads again, the preferred option would always to go with 10 bolt heads and composite gaskets on any rover V8. But if you plan to stick with 14 bolt heads, use metal gaskets.

In regard to getting your heads skimmed, put a straight edge over the head to check if there is any warping, etc. If it checks out there is probably no reason to get it skimmed.

I would also recommend that you switch to ARP studs rather than head bolts. They give a lot better tensioning of the head and will help prevent any issues in the future.
 

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Ian, thanks for the lesson. I like to learn something new. I saw the four extra holes and the note in the manuals saying that no bolts are used on the lower four holes, and figured I had the "10 bolt" heads because it was secured with only ten bolts.

So, since I had composite gaskets on the engine when I got it, and the engine ran very nicely with plenty of power, I wonder if the previous owner who put them in skimmed my heads? I'm not going to pull them off to measure them now, not after all the work to put them on again this winter, so the question will have to wait until some day when these gaskets give up the ghost. With any luck, that will be another 100,000 miles from now. (I have 195,000+ miles now, the "+" because the speedo cable broke just after we bought the truck, and it took me a week to get the replacement and put it in.)

Scott
 

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skucera said:
I wonder if the previous owner who put them in skimmed my heads? I'm not going to pull them off to measure them now, not after all the work to put them on again this winter, so the question will have to wait until some day when these gaskets give up the ghost.
At the end of each head there is a ledge in the casting. It is this point that is used to take any measurements regarding amounts shaved from the heads. I am pretty sure you can do this with the heads on.

Just above the engine number on the block will be the compression ratio. I am pretty sure you will find that you started with a high compression motor.
 

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I definitely have a block marked with 9.0:1 or something like that. (I just took my shoes off after a long day, and I don't want to go out into the rain to check now.) I'll look for that reference ledge this weekend.

Scott
 

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Wow...i just noticed this thread. my 3.5efi has exactly the same symptoms. I was thinking head gasket, which seems to be the findings here.
thanks
 

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Discussion Starter #17
Hi Joe, Having read your other post it sounds like you've definitely got the same problem as me. I've just finished replacing my headgaskets and I've done another compression test and i'm now getting 140psi on all the cylinders. Hope to get the timng reset and the engine fired up on Saturday so fingers crossed!!!
Cheers, Simon
 

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Glad you got yours sorted. Yes, 140psi sounds right compared to the 6x good cylinders on mine. The two I am suspecting that are 'joined' due to the gasket break have very erratic readings, but average less than half the psi of the good ones!

I am pretty sure now I need to change the head gasket. Frustrating at the mo tho, as I've not long just come out of hospital after some full on eye retina surgery, so wont be under (or over) any cars for a few weeks yet until I'm off the healed. (shouldnt even be at my laptop...but hey ho!)

Will update on the other thread once I get out to do the work. cheers
 
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